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Time-bounded program execution

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1. Normal Execution Path print Algol Algol print Algo2 Algo2 print Algo3 Algo3 print Normal Exit QUICK EXIT print Leaving RunPrograms exit end The following is an example pseudo code application pro gram that calls the above functions to perform three algo rithms 1001 Algo2 and Algo3 in a timed execution fash ion Example program execution paths for various timeout conditions are provided below program TimeoutExample N print gt Timeout Example in Thread B call InitTimedExec call StartTimedExec N call RunPrograms call StopTimedExec call UninitTimedExec print lt end The following is an example execution path for the example pseudo code application program where a timeout at 100 ms occurs between Algo2 and Algo3 in RunPro grams gt run TimeoutExample 100 gt Timeout Example in Thread B In InitTimedExec In StartTimedExec In RunPrograms Setup Rollback Check Timeout Condition Normal Execution Path Algol Algo2 Check Timeout Condition Timeout occurred Leaving RunPrograms In StopTimedExec In UninitTimedExec eus Thus when the timeout occurs program execution may be interrupted preventing Algo3 from being performed The program may be reset to the determined rollback state e g to 20 30 35 40 45 50 55 60 65 24 the rollback point and execution resumed with a timeout condition
2. 06 28 ulojs s 1ejnduuoo ulejs s Jejnduuoo v9 jeureju NVM NV 1 US 7 559 060 B2 Sheet 3 of 13 Jul 7 2009 U S Patent 9 AN P sE uonisinboy 09 159 PUN spseog uonisinboy vl OO ce WOMAN O01 d sjuaunijsu paseg sayndwiog 68 XIOMJSN US 7 559 060 B2 Sheet 4 of 13 Jul 7 2009 U S Patent wog 65000 gc 014 ainssald RY URRY 82 P w 4 c8l Way 921 jeubis VOL Pi lt 2 spiced 72 Rg f sx P d ejeq ur 8nig Wogpietj 091 G8L U S Patent Jul 7 2009 Sheet 5 of 13 US 7 559 060 B2 Figure 3A Figure 3B e E c O U S Patent Jul 7 2009 Sheet 6 of 13 US 7 559 060 B2 FIG 4 US 7 559 060 B2 Sheet 7 of 13 Jul 7 2009 U S Patent 9LL SISSE XA 981 IXIN sng 9199 vi EN cel 28 uonisinboy PIED 9199 AUC pJeH L ejeq 02 sng uoisuedx3 991 Jej onuo sng 291 sng 1s0H v94 09L Jej ouo2 99 08 O8plA U S Patent Jul 7 2009 Sheet 8 of 13 US 7 559 060 B2 set timeout condition in a first process 602 initiate execution of a program in a second process 604 the first process determin
3. 30 45 50 55 60 65 8 Visual Solutions ObjectBench by SES Scientific and Engi neering Software and VisiDAQ from Advantech among others The term graphical program includes models or block diagrams created in graphical modeling environments wherein the model or block diagram comprises intercon nected nodes or icons that visually indicate operation of the model or block diagram exemplary graphical modeling envi ronments include Simulink SystemBuild VisSim Hypersig nal Block Diagram etc A graphical program may be represented in the memory of the computer system as data structures and or program instructions The graphical program e g these data struc tures and or program instructions may be compiled or inter preted to produce machine language that accomplishes the desired method or process as shown in the graphical program Input data to a graphical program may be received from any of various sources such as from a device unit under test a process being measured or controlled another computer pro gram a database or from a file Also a user may input data to a graphical program or virtual instrument using a graphical user interface e g a front panel A graphical program may optionally have a GUI associated with the graphical program In this case the plurality of interconnected nodes are often referred to as the block dia gram portion of the graphical program Node In the context of a
4. 40 45 65 10 As shown in FIG 1A the computer system 82 may include a display device operable to display the program as the pro gram is created and or executed The display device may also be operable to display a graphical user interface or front panel of the program during execution of the program The graphi cal user interface may comprise any type of graphical user interface e g depending on the computing platform The computer system 82 may include a memory medium s on which one or more computer programs or software components according to one embodiment of the present invention may be stored For example the memory medium may store one or more programs which are execut able to perform the methods described herein Also the memory medium may store a programming development environment application used to create and or execute such programs The memory medium may also store operating system software as well as other software for operation of the computer system Various embodiments further include receiving or storing instructions and or data implemented in accordance with the foregoing description upon a carrier medium FIG 1B Computer Network FIG 1B illustrates a system including a first computer system 82 that is coupled to a second computer system 90 The computer system 82 may be connected through a network 84 ora computer bus to the second computer system 90 The computer systems 82 and 90 may each be any
5. in response to which the program may exit nor mally The following is an example execution path for the example pseudo code application program where a timeout limit of 1000 ms 1000 ms 1s allows RunPrograms to com plete execution normally run TimeoutExample 1000 gt Timeout Example in Thread B In InitTimedExec In StartTimedExec In RunPrograms Setup Rollback Check Timeout Condition Normal Execution Path Algol Algo2 Algo3 Normal Exit Leaving RunPrograms In StopTimedExec In UninitTimedExec Note that as described above the timeout example pro gram runs in Thread B at critical priority When SetTimeout is called in Start TimedExec control is passed to Thread A also at critical priority to set the timeout event then Thread A goes to sleep returning control back to Thread B Note that when RunPrograms starts Thread B s priority is reduced allowing Thread A to interrupt when awakened by the timeout event In case of a timeout Thread A rolls back Thread B s execution and returns to a sleep state allowing Thread B to resume control at the new execution point the determined rollback point It should be noted that the above functions or substantial equivalents and programs may be implemented as and or invoked from graphical programs as illustrated in FIG 9 described below Implementation of Time Bounded Program Execution Various embodiments of the techniques described herein may thus allo
6. whether timed out or not corresponds to one of a series of items events or processes such as in an automated manufacturing or inspection system For example as FIG 6A shows once the program has exited normally in 608 the method may proceed to 602 and continue as described above e g per forming the time bounded execution of the program in an iterative manner e g executing the program for each of a plurality of items e g objects on a conveyor belt etc Simi larly as also shown in FIG 6A once the program has exited with the timeout condition in 614 the method may proceed to 602 and continue as described above FIG 6B Detailed Method for Time Bounded Program Execution FIG 6B is a more detailed flowchart of a method for time bounded program execution It should be noted that in various embodiments some of the steps may be performed concurrently in a different order than shown or may be omitted Additional steps may also be performed as desired As FIG 6B shows in 622 a timed program execution process may be initiated where the timed program execution process is operable to execute a program in a time bounded manner In a preferred embodiment the timed program execution process comprises a first execution thread Then in 624 a timeout process may be initiated In one embodiment the timeout process executes at a first priority level In a preferred embodiment the timeout process com prises a second executio
7. 060 B2 ae V Initialize Il Set IV Disable Bo meos Ehe Tees Pedo Trent Hri nes Process Event Event Process Thread B Program Execution Normal Exdcution Path ______ _________ t Restore Resource State Exit Code Execution path before timeout Execution path after timeout Point where rollback state was determined Figure 8 U S Patent Jul 7 2009 Sheet 13 of 13 US 7 559 060 B2 Initialize Timed Time Bounded Program Execution Execution Per Iteration Execution Stop Timed Execution Figure 9 US 7 559 060 B2 1 TIME BOUNDED PROGRAM EXECUTION PRIORITY DATA This application claims benefit of priority to U S Provi sional Patent Application Ser No 60 477 388 titled Time Bounded Program Execution filed Jun 10 2003 and whose inventors were Darren R Schmidt Aljosa Vrancic and Satish Kumar FIELD OF THE INVENTION The present invention relates to real time program execu tion and more particularly to a system and method for time bounded program execution DESCRIPTION OF THE RELATED ART Many industrial systems require real time operation such as for example automated manufacturing control and qual ity control where an algorithm or operation or set of opera tions must be performed under strict time limitations for each of a series of items e g on a moving assembly or manufactur
8. for processing the next item is to begin The timed program execution process may then perform a time bounded execution of the program or a plurality of programs In one embodiment the execution ofthe program may be performed at a second priority level where the second priority level is below the first priority level In other words the process that executes the program preferably operates at a priority level below that of the timeout process so that the timeout process can reliably preempt the execution process as necessary A preferred embodiment of the program execution step is described below As noted above in one embodiment the method may execute a plurality of programs For example the time bounded program execution may be performed in an iterative manner where at each iteration a respective program is executed The timeout event may then be disabled and the timeout process may be terminated In other words cleanup opera tions for the timeout process may be performed In one embodiment once the timeout event has been disabled the method may return to setting the timeout event and may execute the program or programs proceeding as described above In other words the program or programs may be performed iteratively where for each iteration the timeout event is set the program executed and the timeout disabled e g for each ofa plurality of items e g on an assembly line or conveyor belt Thus each program or
9. may return to the set timeout condition step above and continue as described e g per forming the time bounded execution of the program in an iterative manner e g executing the program for each of a plurality of items e g objects on a conveyor belt etc Simi larly once the program has exited with the timeout condition US 7 559 060 B2 3 the method may proceed back to setting the timeout condi tion and continue as described above In another embodiment of the present invention a timed program execution process may be initiated where the timed program execution process is operable to execute a program in a time bounded manner In a preferred embodiment the timed program execution process comprises a first execution thread Then a timeout process may be initiated In one embodi ment the timeout process executes at a first priority level In a preferred embodiment the timeout process comprises a second execution thread In one embodiment initiating the timeout process may be performed by the timed program execution process A timeout event may then be configured or set Note that the timeout event may be based on a timer a signal from an external process and or any other type of event For example acontrol process or sensoron a conveyor belt or assembly line may send a signal indicating that a next item has arrived and so indicate that the time period for processing the current item is over and that the time period
10. terminated In other words cleanup operations for the timeout process may be performed As 0 jak 5 25 35 40 45 60 65 18 FIG 6B also indicates in one embodiment once the timeout event has been disabled in 630 the method may return to 626 setting the timeout event and executing the program or pro grams time bounded and proceeding as described above In other words the program or programs may be performed iteratively where for each iteration the timeout event is set the program executed and the timeout disabled e g for each ofa plurality of items e g on an assembly line or conveyor belt Thus each program or set of programs may be per formed in a time bounded manner a plurality of times Finally in 634 the timed program execution process may be terminated Thus the timed program execution may be performed for each item in a series of items being processed or analyzed e g items queued for processing on the assembly line or conveyor belt A more detailed embodiment of the timed program execution of step 618 is described below with refer ence to FIG 6C FIG 6C Time Bounded Execution of the Program FIG 6C is a more detailed flowchart of one embodiment of step 628 of the method of FIG 6B It should be noted that in various embodiments some of the steps may be performed concurrently in a different order than shown or may be omitted Additional steps may also be performed a
11. the program US 7 559 060 B2 27 3 configuring a timeout event wherein the timeout event is an event indicating a timeout condition for the program 4 the timed program execution process performing a time bounded execution of the program comprising a determining and storing a rollback state for the pro gram b if the timeout event has not occurred executing the program wherein during said executing if the tim eout event occurs the timeout process setting the timed program execution process to the rollback state and dis abling the timeout event and d the timed program execution process resuming executing the program based on the rollback state with a timeout condition in preparation to perform a program exit procedure and performing the program exit procedure thereby ter minating execution of the program 5 disabling the timeout event 6 terminating the timeout process and 7 terminating the timed program execution process 2 The memory medium of claim 1 wherein e further comprises clearing the rollback state 3 The memory medium of claim 2 wherein the program instructions are further executable to perform iteratively performing said time bounded execution of a plurality of programs 4 The memory medium of claim 3 wherein said iteratively performing comprises for each of the plurality of programs performing a through e 5 The memory medium of claim 4 wherein e further co
12. to one embodiment and FIG 9 illustrates an example implementation of the meth ods of FIGS 6A 6C according to one embodiment While the invention is susceptible to various modifications and alternative forms specific embodiments thereof are shown by way of example in the drawings and are herein described in detail It should be understood however that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed but on the contrary the intention is to cover all modifications equiva 20 25 30 35 40 45 50 55 60 65 6 lents and alternatives falling within the spirit and scope ofthe present invention as defined by the appended claims DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Incorporation by Reference The following references are hereby incorporated by ref erence in their entirety as though fully and completely set forth herein U S Provisional Patent Application Ser No 60 477 388 titled Time Bounded Program Execution filed Jun 10 2003 and whose inventors were Darren R Schmidt Aljosa Vrancic and Satish Kumar U S Pat No 4 914 568 titled Graphical System Mod eling a Process and Associated Method issued on Apr 3 1990 U S Pat No 6 173 438 titled Embedded Graphical Pro gramming System filed Aug 18 1997 0 8 Pat No 6 219 628 titled System and Method for Configuring an Instrument to Perform
13. up to three rollback points may be utilized per program to properly manage timeouts Of course the number of rollback points or states used may be smaller or greater than three as needed Detailed Embodiment of the Process of FIG 8 An example embodiment of the process of FIG 8 is described below in terms of pseudo code It should be noted that the example shown is intended to be exemplary only and is not intended to limit the invention to any particular imple mentation form or functionality The following pseudo code represents one embodiment of a set of functions that may be invoked from an application program to provide time bounded execution functionality routine InitTimedExec print In InitTimedExec CreateTimeoutThread creates Thread A CreateResourceManagers end routine StartTimedExec time print In StartTimedExec EnableResources SetTimeout time calls Thread A end routine StopTimedExec print In StopTimedExec ClearTimeout DisableResources end routine UninitTimedExec print In UninitTimedExec DestroyTimeoutThread DestroyResourceManagers US 7 559 060 B2 23 continued end routine RunPrograms print In RunPrograms print Setup Rollback ReduceThreadPriority StoreResourceState SetRollbackPoint print Check Timeout Condition if Timeout occurred print Timeout occurred RestoreResourceState goto QUICK EXIT end print
14. 9 46 2006 01 configured in the timeout process at a first priority level and G06F 9 44 2006 01 a rollback state determined for the program Execution of the G06F 11 00 2006 01 program is initiated in the timed program execution process at 52 U S CL enn 718 100 718 102 718 104 a second priority level below the first priority level During 717 24 717 127 717 128 717 129 717 131 execution of the program the timeout process determines if 714 2 714 34 714 48 714 55 the timeout condition has occurred and if so the timeout 58 Field of Classification Search 718 1 108 process restores the execution of the program to the rollback 714 17 34 2 15 55 48 712 23 234 228 state and the timed program execution process resumes 717 174 11 168 178 120 131 execution of the program from the rollback state with the See application file for complete search history timeout condition The program exits in the timed program execution process in response to the timeout condition and 56 References Cited the timeout event disabled The timeout process is terminated U S PATENT DOCUMENTS and the timed program execution process is terminated 5 530 802 A 6 1996 Fuchs etal 714 17 5 944 778 8 1999 Takeuchi et al 718 100 27 Claims 13 Drawing Sheets Perform Time Bounded Execution of Program set execution priority level of timed program execution process to second priority level belo
15. Execution Per Iteration section of the graphical pro gram The scaled time limit may then be passed to the time bounded VI containing the optimization VI Thus the numerical optimization process may be embed ded or included in the time bounded program execution infra structure shown in FIG 9 and may thus be constrained to execute within specified time limits It should be noted that the examples described above are exemplary only and that various embodiments of the present invention are contemplated for use in any type of application domain system or process where program execution is to be performed in a time bounded manner Although the embodiments above have been described in considerable detail numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated It is intended that the follow ing claims be interpreted to embrace all such variations and modifications We claim 1 A computer accessible memory medium that stores pro gram instructions for performing time bounded execution of a program wherein the program instructions are executable by a processor to perform 1 initiating a timed program execution process wherein the timed program execution process is configured to execute a program in a time bounded manner 2 initiating a timeout process wherein the timeout process is configured to preempt the execution process to inter rupt execution of
16. Measurement Func tions Utilizing Conversion of Graphical Programs into Hard ware Implementations filed Aug 18 1997 Terms The following is a glossary of terms used in the present application Deterministic Program Determinism or a deterministic program relates to execution time of a program not repro ducible results A deterministic program completes execution in a predictable and repeatable amount of time for any valid input set Jitter The maximum variance in execution time from one run ofthe program to the next Smaller jitter represents a more deterministic behavior Resource Contention Also referred to as a resource con flict in a real time system refers to two or more processes demanding access to the same resource at overlapping time intervals For example a common resource contention occurs when two processes request memory from the system s memory manager Only one process is allowed access at a time and so the other is forced to wait possibly resulting in unpredictable behavior in execution that may prevent deter ministic execution Point By Point Algorithms typically iterative algo rithms that have been redesigned for a real time system to perform one iteration per execution This may require the program to maintain state information so that the following iteration starts from where the prior iteration left off Time Bounded Program a program that obeys a time limit t by completing execution with a re
17. Note that in this embodiment the block labeled Initialize Timed Execution refers to initiating the timeout process described above the block labeled Start Timed Execution refers to setting the timeout event the block labeled Stop Timed Execution refers to disabling the timeout event and the block labeled Un initialize Timed Execution refers to terminating the timeout process In one embodiment the initiation and termination of the timed pro gram execution process described above may occur prior to and after the block diagram respectively In one embodiment the time bound program execution may be performed in the following way where the process is presented in five stages I V I Initialize Timed Execution a Instantiate timeout mechanism b Preallocate all resources needed by the programs to run and initialize managers for these resources II Start Timed Execution a Enable the resource managers so that all request for resources are handled by them until the timed execu tion is stopped b Start the timeout mechanism III Run Program s for each individual program do the following a If a timeout has occurred in a prior program exit immediately b Store the state of resources handled by each resource manager c Establish a rollback state e g a rollback point d Execute the program as usual e Ifa rollback occurs 1 Restore the state of the resources handled by each resource mana
18. OF THE DRAWINGS A better understanding of the present invention can be obtained when the following detailed description of the pre ferred embodiment is considered in conjunction with the following drawings in which FIG 1A illustrates a computer system operable to execute a program according to an embodiment of the present inven tion FIG 1B illustrates a network system comprising two or more computer systems that may implement an embodiment of the present invention FIG 2A illustrates an instrumentation control system according to one embodiment of the invention FIG 2B illustrates an industrial automation system accord ing to one embodiment of the invention FIG is a high level block diagram of an exemplary system which may execute or utilize programs according to the present invention FIG 3B illustrates an exemplary system which may per form control and or simulation functions utilizing programs according to the present invention FIG 4 illustrates a machine vision system in an automated manufacturing application according to one embodiment FIG 5 is an exemplary block diagram of the computer systems of FIGS 1A 1B 2A 2B 3B and 4 FIGS 6A 6C are flowchart diagrams illustrating various embodiments of a method for time bounded execution of a program FIG 7 illustrates process flow of timed execution accord ing to one embodiment FIG 8 illustrates a more detailed example of timeout behavior according
19. The expansion bus 170 may be the PCI Periph 10 20 25 30 35 40 45 50 55 60 65 14 eral Component Interconnect expansion bus although other bus types can be used The expansion bus 170 includes slots for various devices such as described above The computer 82 further comprises a video display subsystem 180 and hard drive 182 coupled to the expansion bus 170 As shown a device 190 may also be connected to the computer The device 190 may include a processor and memory which may execute a real time operating system The device 190 may also or instead comprise a programmable hardware element The computer system may be operable to deploy a program to the device 190 for execution of the program on the device 190 The deployed program may take the form of graphical program instructions or data structures that directly represent the program functionality Alterna tively the deployed program may take the form of text code e g C code generated from a graphical program As another example the deployed program may take the form of com piled code generated from the program Time Bounded Program Execution Overview Of the restrictions imposed by determinism the upper limit on execution time is extremely valuable and provides the time behavior desired for many domains of operations While determinism demands that a result is generated in a certain time frame time bounded execution requires a result or a time
20. US007559060B2 az United States Patent 10 Patent No US 7 559 060 B2 Schmidt et al 45 Date of Patent Jul 7 2009 54 TIME BOUNDED PROGRAM EXECUTION 6 014 669 A 1 2000 Slaughter et al 707 10 6 076 157 6 2000 Borkenhagen et al 712 228 75 Inventors Darren R Schmidt Cedar Park TX 6 161 193 A 12 2000 Gargetal 714 6 US Aljosa Austin TX US 6 185 577 Bl 2 2001 Nainani et al 707 202 Satish V Kumar Austin TX US 6 189 022 2 2001 Binns 718 100 73 Assignee National Instruments Corporation Austin TX US Continued Notice Subject to any disclaimer the term of this patent is extended or adjusted under 35 OTHER PUBLICATIONS U S C 154 b by 992 days LabVIEW Real Time Module User Manual Apr 2003 21 Appl No 10 784 866 Continued 22 Filed Feb 23 2004 Primary Examiner Van H Nguyen Assistant Examiner Abdullah Al Kawsar 65 Prior Publication Data 74 Attorney Agent or Firm Meyertons Hood Kivlin US 2004 0255296 A1 Dec 16 2004 Kowert amp Goetzel P C Jeffrey C Hood Mark S Williams Related U S Application Data 67 ABSTRACT 60 Provisional application No 60 477 388 filed on Jun 10 2003 System and method for performing time bounded execution ofa program A timed program execution process is initiated 51 Int Cl and a timeout process is initiated A timeout condition is G06F
21. abled state to avoid rolling back to an unstable process state For this an 5 40 45 60 65 20 reason the rollback mechanism may be disabled during por tions of fundamental resource operations or other operations that involve an unstable process state For example in one embodiment performing time bounded execution of the program step 618 of FIG 6B may include receiving a disable request from the program to dis able the rollback state and disabling the rollback state in response to said disable request The program may then con tinuing execution e g performing a memory allocation etc while the rollback state is disabled An enable request may then be received from the program to enable the rollback state e g once the memory allocation is done and the roll back state enabled in response to the enable request The rollback state for the program may then be updated In one embodiment enabling the rollback state may include check ing to see if a timeout event occurred while disabled and performing a rollback if it did In another embodiment this check may be performed as a part of the rollback update Note that this type of protection against rolling back to an unstable state is necessary for any system calls that degrade the process state if stopped prematurely FIG 7 High Level Example of Time Bound Program Execution FIG 7 high level block diagram illustrating time bound program execution
22. am and un ini tializing the one or more resource managers for the one or more resources Note also that in some embodiments the releasing one or more resources may be performed before the un initializing the one or more resources managers while in other embodiments the un initializing the one or more resources managers may be performed first and or may include the releasing US 7 559 060 B2 5 In another embodiment initiating the timeout process may further include enabling each of the one or more resource managers and terminating the timeout process further may include disabling each ofthe one or more resource managers Note that the resources may include any type of resource used by the program and or by the timed program execution process and or by the timeout process For example in one embodiment the one or more resources include one or more memory pools for memory allocations during the time bounded execution of the program In one embodiment prior to determining the rollback state e g the rollback point in the program a respective resource state for each ofthe one or more resources may be stored and each of the one or more resource managers may be enabled In this embodiment per forming the program exit procedure may include if the tim eout event has occurred restoring the respective resource state for each of the one or more resources and disabling each of the one or more resource managers BRIEF DESCRIPTION
23. an additional callback mechanism is typically be required to allow the user to define other states in which the optimization may exit This mechanism must generally be built in to the optimization routine at design time The use of this mechanism is usually driven by the need to limit the execution time of the optimi zation Classes of functions that behave well for a specific optimization approach require roughly the same number of iterations to converge and hence take roughly the same amount of time to compute if the time to evaluate the func tion is similar Functions not suited for this type of optimi zation may require a much larger number of iterations and thus generally exceed desired execution times However lim iting iterations punishes functions that evaluate quickly but have slower convergence and so this approach may introduce undesired biases The above infrastructure may be used to solve this type of problem in numeric optimization As with the blob analysis example an optimization VI may replace the VI in the Run Program s section The Time Limit ms input should be set to the maximum amount of time the application permits for one optimization to take place In one embodiment this limit may be scaled in accordance with the time required by the function to be evaluated so that optimizing more complex functions may be allowed more time Code performing this scaling may be placed in the loop of the Time Bounded Pro gram
24. an icon representing a clock and an instrument interface that is itself a graphical program shown expanded in the bottom section of FIG 9 As shown the expanded graphical program may include a Start Timed Execution section a Run Program s section and a Stop Timed Execution section as well as vari ous node providing input and output for the sections Addi tionally the Run Program s section preferably includes a program node or a collection of program nodes also referred to as a virtual instrument VI or collection of VIs whose processing time is to be limited In other words the graphical program node shown in the Run Program s section comprises the program whose execution is to be time bounded Please refer to FIGS 7 and 8 described above for further details of each section Example Machine Vision For an example in the machine vision domain consider an application needed to inspect the number of surface imper fections in a camera lens Given a digital image of the lens this type of inspection may achieved by counting the number ofblobs in animage ofthe lens For example in IMAQ Vision 7 a machine vision application provided by National Instru ments Corporation this processing may be performed using an IMAQ Particle Analysis VI Under normal circumstances acamera lens should have at most 10 15 detectable blemishes and hence should contain no more than 15 blobs Assume the execution time to process the di
25. ay be trying to develop The plant 94 repre sents the system the user may be trying to control For 20 25 30 35 40 45 50 55 60 65 12 example if the user is designing an ECU for a car the con troller 92 is the ECU and the plant 94 is the car s engine and possibly other components such as transmission brakes and so on As shown a user may create a program that specifies or implements the functionality of one or both ofthe control ler 92 and the plant 94 For example a control engineer may use a modeling and simulation tool to create a model pro gram ofthe plant 94 and or to create the algorithm program for the controller 92 FIG 3B illustrates an exemplary system which may per form control and or simulation functions As shown the con troller 92 may be implemented by a computer system 82 or other device e g including a processor and memory medium and or including a programmable hardware element that executes or implements a program In a similar manner the plant 94 may be implemented by a computer system or other device 144 e g including a processor and memory medium and or including a programmable hardware element that executes or implements a program or may be implemented a real physical system e g a car engine Inone embodiment ofthe invention one or more programs may be created which are used in performing rapid control prototyping Rapid Control Prototyping RCP generally ref
26. bove the rollback state may include a rollback point in the program and so the second process may resume execution of the program from the rollback point Finally a program exit procedure may be performed In one embodiment performing the program exit procedure may include clearing the rollback state e g clearing the rollback point In one embodiment the program may exit with an error code indicating the timeout condition as described above As noted above in one embodiment the method may include iteratively performing time bounded execution of a plurality of programs For example in one embodiment iteratively performing the time bounded execution of a plu rality of programs may include performing the method described above for each of the plurality of programs In one embodiment performing the program exit proce dure may also include if the timeout event has occurred storing an indication of a timeout condition where the timed program execution process performing a time bounded execution of the program includes performing the method above for each program only if the timeout condition is not indicated Thus in a preferred embodiment each of the methods described herein may be performed in an iterative manner where each program or each of a set of programs is per formed as described above for each of a plurality of items processes or events such as for example items on an assem bly line or conveyor belt In an embo
27. c or field programmable devices FPDs such as one or more FPGAs Field Programmable Gate Arrays or one or more PLDs Programmable Logic Devices such as one or more Simple PLDs SPLDs or one or more Complex PLDs CPLDs or other types of program mable hardware programmable hardware element may also be referred to as reconfigurable logic Medium includes one or more of a memory medium carrier medium and or programmable hardware element encompasses various types of mediums that can either store program instructions data structures or can be configured with a hardware configuration program Program the term program is intended to have the full breadth of its ordinary meaning The term program includes 1 a software program which may be stored in a memory and is executable by a processor or 2 a hardware configuration program useable for configuring a program mable hardware element Software Program the term software program is intended to have the full breadth of its ordinary meaning and includes any type of program instructions code script and or data or combinations thereof that may be stored ina memory medium and executed by a processor Exemplary software programs include programs written in text based program ming languages such as C Pascal Fortran Cobol Java assembly language etc graphical programs programs writ ten in graphical programming languages assembly language program
28. combination thereof In the machine vision system of FIG 4 computer system 102 is coupled to a camera 112 via bus 122 and operates to receive one or more images e g of items to be inspected The computer system 102 may be operable to perform various machine vision tasks e g pattern characterization or match ing programs to analyze the images e g for quality control In the example illustrates in FIG 4 ifthe analysis determines that an item does not meet specified quality standards the item may be discarded There may be restrictions on the time allowed per item for performance of the tasks and so time bounded execution of the task programs may be enforced in accordance with embodiments of the present invention In other words embodiments of the present invention may be used to limit the time spent performing the tasks per item to some specified duration For example in one embodiment if the time spent performing the tasks on a given item meets or exceeds the specified duration the item may be marked or removed for further processing and analysis and the next item considered In this way the item that failed the time bounded limitation may receive further processing or analysis as needed e g offline while processing of subsequent items in the queue on the assembly or inspection line continues without delay or interruption Further details of time bounded execution are provided below FIG 5 Computer System Block Diag
29. d then the program may complete and exit normally If the timeout condition does occur the first process may restore the program to a pre defined state in the program referred to as the rollback state In a preferred embodiment the rollback state includes a roll back point in the program from which the program may exit normally e g with a timeout condition Once the program has been restored to the pre defined state e g to the rollback state the second process may execute the program from the rollback state with the error timeout condition In other words the second process e g thread may resume execution of the program from the roll back state In a preferred embodiment the program may resume execution from the rollback point Finally the program may exit in the second process in response to the timeout condition e g with an error code indicating that program execution was interrupted In other words the program did not complete execution before the timeout occurred and so the program execution may be inter rupted and reset for subsequent execution It should be noted that in preferred embodiments the method described above may be performed iteratively where for example each time bounded program execution whether timed out or not corresponds to one of a series of items events or processes such as in an automated manufacturing or inspection system For example once the program has exited normally the method
30. diment where the pro gram includes one or more sub programs or where the pro gram comprises a set of programs executing the program may include performing the above steps for each ofthe one or more sub programs or for each ofthe set ofprograms In other words the priority level set for the program may apply to each of the sub programs or the set of programs In one embodiment setting the execution priority level of the timed program execution process may include storing an original execution priority level of the timed program execu tion process prior to setting the execution priority level ofthe timed program execution process In this embodiment per forming the program exit procedure may also include restor ing the execution priority level of the timed program execu tion process to the original execution priority level In one embodiment initiating the timeout process may include acquiring one or more resources for the time bounded execution of the program and initializing one or more resource managers for the one or more resources Note that in some embodiments the acquiring one or more resources may beperformed before the initializing the one or more resources managers while in other embodiments the initializing the one or more resources managers may be performed first and or may include the acquiring Terminating the timeout process may then include releasing the one or more resources for the time bounded execution of the progr
31. e are directly related to the number of blobs found in an input image According to determinism requirements execu tion time and resource usage should not vary over different valid inputs Hence these programs or algorithms are not suited for deterministic execution Algorithms for pattern matching and edge detection have similar challenges that make determinism unfeasible Thus improved systems and methods for time bounded program execution are desired SUMMARY OF THE INVENTION Various embodiments of the present invention provide for time bounded execution of programs such as in real time applications In one embodiment a timeout condition may be set ina first process e g a first thread For example a timeout event may be configured or set such that the event will fire when a specified amount of time has elapsed Execution of a program may be initiated in a second process e g a second thread It should be noted that in other embodiments the second process may include two or more execution threads or processes e g a plurality of second threads Note that in some embodiments execution of the program may include execution of a plurality of programs For example in one embodiment the program may include one or more sub programs i e the program may comprise a set of programs During execution of the program the first process may determine if the timeout condition has occurred and if the timeout condition has not occurre
32. e or more instruments may include a GPIB instru ment 112 and associated GPIB interface card 122 a data acquisition board 114 and associated signal conditioning cir cuitry 124 a VXI instrument 116 a PXI instrument 118 a video device or camera 132 and associated image acquisition or machine vision card 134 a motion control device 136 and associated motion control interface card 138 and or one or more computer based instrument cards 142 among other types of devices The computer system may couple to and operate with one or more of these instruments The instru ments may be coupled to a unit under test UUT or process 150 or may be coupled to receive field signals typically generated by transducers The system 100 may be used in a data acquisition and control application in a test and mea surement application an image processing or machine vision application a process control application a man machine interface application a simulation application or a hardware in the loop validation application and a data analysis appli cation among others FIG 2B illustrates an exemplary industrial automation system 160 which may implement embodiments ofthe inven tion The industrial automation system 160 is similar to the instrumentation or test and measurement system 100 shown in FIG 2A Elements which are similar or identical to ele ments in FIG 2A have the same reference numerals for con venience The system 160 may comprise a comput
33. e respective resource state for each ofthe one or more resources and disabling each of the one or more resource managers 14 The memory medium ofclaim 1 wherein said initiating the timeout process is performed during said executing 15 The memory medium of claim 1 wherein the program comprises one or more sub pro grams and wherein b further comprises performing a through e for each of the one or more sub programs 16 The memory medium of claim 1 wherein said initiating thetimeout process is performed by the timed program execu tion process 17 The memory medium of claim 1 wherein the rollback state comprises rollback point comprising an execution point in the pro gram and an execution state ofthe timed program execution process at the rollback point 18 The memory medium of claim 1 wherein the program comprises a subprogram and wherein said executing the program further comprises 8 initiating another timeout process 9 configuring another timeout event 10 the timed program execution process performing a time bounded execution of the subprogram compris ing f determining and storing another rollback state for the subprogram g if the another timeout event has not occurred execut ing the subprogram wherein during said executing the subprogram if the another timeout event occurs US 7 559 060 B2 29 h the another timeout process setting the timed program execution process to the anot
34. er 82 which connects to one or more devices or instruments The computer 82 may comprise a CPU a display screen memory and one or more input devices such as a mouse or keyboard as shown The computer 82 may operate with the one or more devices to a process or device 150 to perform an automation function such as MMI Man Machine Interface SCADA Supervisory Control and Data Acquisition portable or dis tributed data acquisition process control advanced analysis or other control among others The one or more devices may include a data acquisition board 114 and associated signal conditioning circuitry 124 a PXI instrument 118 a video device 132 and associated image acquisition card 134 a motion control device 136 and asso ciated motion control interface card 138 a fieldbus device 170 and associated fieldbus interface card 172 a PLC Pro grammable Logic Controller 176 a serial instrument 182 and associated serial interface card 184 or a distributed data acquisition system such as the Fieldpoint system available from National Instruments among other types of devices FIG is a high level block diagram of an exemplary system which may execute or utilize programs according to embodiments of the present invention FIG 3A illustrates a general high level block diagram of a generic control and or simulation system which comprises a controller 92 and a plant 94 The controller 92 represents a control system algo rithm the user m
35. ers to the process by which a user develops a control algorithm and quickly executes that algorithm on a target controller connected to a real system The user may develop the control algorithm using a program and the program may execute on the controller 92 e g on a computer system or other device The computer system 82 may be a platform that supports real time execution e g a device including a pro cessor that executes a RTOS ora device including a program mable hardware element Inone embodiment ofthe invention one or more programs may be created which are used in performing Hardware in the Loop HIL simulation Hardware in the Loop HIL refers to the execution of the plant model 94 in real time to test opera tion of a real controller 92 For example once the controller 92 has been designed it may be expensive and complicated to actually test the controller 92 thoroughly in a real plant e g arealcar Thus the plant model implemented by a program is executed in real time to make the real controller 92 believe or operate as if it is connected to a real plant e g real engine Inthe embodiments of FIGS 2A 2B 3B and 4 above one or more ofthe various devices may couple to each other over a network such as the Internet In one embodiment the user operates to select a target device from a plurality of possible target devices for programming or configuration using a pro gram Thus the user may create a program
36. es if the timeout condition occurs during program execution NO program exits normally 612 606 the first process restores program to pre defined point in program 608 timeout condition 607 YES the program exits from the pre defined point 610 Figure 6A U S Patent Jul 7 2009 Sheet 9 of 13 US 7 559 060 B2 initiate timed execution process 612 initiate timeout process 614 set timeout event 616 perform time bounded execution of program 618 disable timeout event 620 terminate timeout process 622 terminate timed program execution process 622 Figure 6B U S Patent Jul 7 2009 Sheet 10 of 13 US 7 559 060 B2 Perform Time Bounded Execution of Program 618 set execution priority level of timed program execution process to second priority level below first priority level of timeout process 632 determine rollback point in program 634 YES exit 650 timeout event NO execute program 636 rollback program and imeout event during resume execution program execution from rollback point 638 perform program exit procedure 640 Figure 6C US 7 559 060 B2 Sheet 11 of 13 Jul 7 2009 U S Patent SS920Jg ezijeniulu A sIqesiq AI 2 aniy 5 uny Il jue 3 195 SS8901q ezyeniu I U S Patent Jul 7 2009 Sheet 12 of 13 US 7 559
37. exit procedure thereby terminating execution of the other program 11 disabling the another timeout event and 12 terminating the another timeout process 21 The memory medium of claim 1 wherein said execut ing the program further comprises receiving a disable request from the program to disable the rollback state disabling the rollback state in response to said disable request receiving an enable request from the program to enable the rollback state enabling the rollback state in response to said enable request and updating the rollback state for the program 22 The memory medium of claim 1 wherein the program comprises a machine vision applica tion 23 The memory medium of claim 1 wherein the program comprises a numerical analysis appli cation 24 The memory medium of claim 1 wherein the program comprises a text based program 25 The memory medium of claim 1 wherein the program comprises a graphical program 26 A system for performing time bounded execution of a program wherein the system comprises a processor and a memory coupled to the processor wherein the memory stores program instructions executable by the processor to 20 25 35 40 45 50 55 60 30 1 initiate a timed program execution process wherein the timed program execution process is configured to execute a program in a time bounded manner 2 initiate a timeout process wherein the timeout process is config
38. f a graphical user interface such as for providing input or dis playing output Exemplary graphical user interface elements comprise input controls and output indicators Input Control a graphical user interface element for pro viding user input to a program Exemplary input controls comprise dials knobs sliders input text boxes etc Output Indicator a graphical user interface element for displaying output from a program Exemplary output indica tors include charts graphs gauges output text boxes numeric displays etc An output indicator is sometimes referred to as an output control Computer System any of various types of computing or processing systems including a personal computer system PC mainframe computer system workstation network appliance Internet appliance personal digital assistant PDA television system grid computing system or other device or combinations of devices In general the term com puter system can be broadly defined to encompass any device or combination of devices having at least one pro cessor that executes instructions from a memory medium Measurement Device includes instruments data acqui sition devices smart sensors and any of various types of devices that are operable to acquire and or store data A mea surement device may also optionally be further operable to analyze or process the acquired or stored data Examples of a measurement device include an instrument suc
39. ger ii Handle the error condition and exit the program f Otherwise exit the program as usual IV Stop Timed Execution a Stop the timeout mechanism b Disable the resource managers so that all requests for resources are handled as usual US 7 559 060 B2 21 V Un initialize Timed Execution a Free up the timeout mechanism b Free all resources controlled by the resource manag ers Thus the above process may facilitate time bounded execution of a program or of a plurality of programs and may also include performing initialization I and cleanup V operations related to the program execution Note that the above description is meant to be exemplary only and is not intended to limit the method or process to any particular set of steps or to any particular organization of steps For example in one embodiment the above method may be performed in three stages e g I II III amp IV V As another example the indicated loop may not be required although such loops are common in applications As yet another example if the programs to run do not require any dynamic system resources then the following steps may not be required I b II a III b III e sub i IV b and V b FIG 8 Process Flow FIG 8 illustrates a high level flow of the process of FIG 7 from the start of the timer the setting of the timeout event through the program execution including the recognition ofa timeout event and subsequent ex
40. gital image of an acceptable camera lens is roughly 5 ms milliseconds However the image ofa bad lens having 100 or more surface problems may cause the blob inspection s execution time to jump as much as 10 times or gt 50 ms for this example and thus time bounded program execution may be desirable Using the above infrastructure of FIG 9 the Time Limit ms input may be set to a value of approximately 10 ms This time limit may allow for some variation in performance but may avoid spending excessive amounts of time processing images of bad lenses with many blemishes In this example the VI in the Run Program s section may be replaced by the IMAQ Particle Analysis VI or equivalent and a trivial check made to see if this VI process a timed out or b found more 20 25 30 40 45 50 55 60 65 26 than 15 blobs If either of these conditions is true a failure condition may be returned from the VI e g via an Error Out node as shown Note that in this example a node is provided indicating the Execution Time in milliseconds Example Numerical Analysis numerical analysis domain can provide another spe cific example Consider a numerical optimization process where determination of a minimum value of a function is required Many optimization routines are based on iterative processes If the optimization routine is to be interrupted before its result conditions tolerances are met
41. graphical program an element that may be included in a graphical program A node may have an associated icon that represents the node in the graphi cal program as well as underlying code or data that imple ments functionality of the node Exemplary nodes include function nodes terminal nodes structure nodes etc Nodes may be connected together in a graphical program by con nection icons or wires Data Flow Graphical Program or Data Flow Diagram A graphical program or diagram comprising a plurality of inter connected nodes wherein the connections between the nodes indicate that data produced by one node is used by another node Graphical User Interface this term is intended to have the full breadth of its ordinary meaning The term Graphical User Interface is often abbreviated to A GUI may comprise only one or more input GUI elements only one or more output GUI elements or both input and output GUI elements The following provides examples of various aspects of GUIs The following examples and discussion are not intended to limit the ordinary meaning of GUI but rather provide examples of what the term graphical user interface encompasses A GUI may comprise a single window having one or more GUI Elements or may comprise a plurality ofindividual GUI Elements or individual windows each having one or more GUI Elements wherein the individual GUI Elements or windows may optionally be tiled together A GUI
42. h as a tradi tional stand alone box instrument a computer based instrument instrument on a card or external instrument a data acquisition card a device external to a computer that operates similarly to a data acquisition card a smart sensor one or more DAQ or measurement cards or modules in a chassis an image acquisition device such as an image acqui sition or machine vision card also called a video capture board or smart camera a motion control device a robot having machine vision and other similar types of devices Exemplary stand alone instruments include oscilloscopes multimeters signal analyzers arbitrary waveform genera tors spectroscopes and similar measurement test or auto mation instruments measurement device may be further operable to perform control functions e g in response to analysis ofthe acquired or stored data For example the measurement device may send a control signal to an external system such as a motion control system or to a sensor in response to particular data A measurement device may also be operable to perform auto mation functions i e may receive and analyze data and issue automation control signals in response FIG 1A Computer System FIG 1A illustrates a computer system 82 operable to execute a program configured to execute in a time bounded manner One embodiment of a method for time bounded program execution is described below 0 an 5 20 25
43. her rollback state and disabling the another timeout event and 1 the timed program execution process resuming executing the subprogram based on the another roll back state with another timeout condition and j performing a subprogram exit procedure thereby ter minating execution of the subprogram 11 disabling the another timeout event and 12 terminating the another timeout process 19 The memory medium of claim 18 wherein j further comprises e 20 The memory medium of claim 1 wherein the program instructions are further executable to perform time bounded execution of another program substantially in parallel with the time bounded execution of the program by 8 initiating another timeout process 9 configuring another timeout event 10 the timed program execution process performing a time bounded execution of the another program com prising f determining and storing another rollback state for the another program g if the another timeout event has not occurred execut ing the another program wherein during said execut ing the another program if the another timeout event Occurs h the another timeout process setting the timed program execution process to the another rollback state and disabling the another timeout event and i the timed program execution process resuming executing the another program based on the another rollback state with another timeout condition and j performing another program
44. ime bounded execution of the program and 25 30 35 40 45 50 55 60 65 28 initializing one or moreresource managers forthe one or more resources and wherein said terminating the timeout process comprises releasing the one or more resources for the time bounded execution of the program and un initializing the one or more resource managers for the one or more resources 10 The memory medium of claim 9 wherein said initiating the timeout process further com prises creating each ofthe one or more resource managers and wherein said terminating the timeout process further com prises deleting each of the one or more resource managers 11 The memory medium of claim 9 wherein said initiating the timeout process further com prises enabling each ofthe one or more resource managers and wherein said terminating the timeout process further com prises disabling each of the one or more resource managers 12 The memory medium of claim 9 wherein said one or more resources comprises one or more memory pools for memory allocations during the time bounded execution of the program 13 The memory medium of claim 9 wherein prior to a the program instructions are farther executable to perform storing a respective resource state for each of the one or more resources and enabling each of the one or more resource managers wherein e further comprises if the timeout event has occurred restoring th
45. impossible Using embodiments of the techniques dis closed herein these constraints may not apply and so a much larger set of algorithms may be considered time boundable FIG 9 Example Implementation FIG 9 illustrates time bounded execution in a LabVIEW application according to one embodiment More specifically FIG 9 illustrates an embodiment of the present invention where the program and the time bounded execution process are implemented in graphical program code specifically as LabVIEW graphical programs It should be noted that the particular implementation of FIG 9 is intended to be exem plary only and is not intended to limit the form function or appearance of the invention to any particular implementa tion In other words the time bounded program execution techniques described herein are considered to be broadly applicable to any process where a program text based or graphical is required to execute in a time bounded manner As FIG 9 shows a top level graphical program may include an Initialize Time Execution portion a Time Bounded Program Execution portion and an Uninitialize Time Execution portion Note that the Time Bounded Pro gram Execution portion of the graphical program includes a loop structure for iteratively performing the program in a time bounded manner e g once per item on an assembly line As FIG 9 also shows the Time Bounded Program Execu tion portion includes a graphical program node with
46. ing line Increasingly such operations are per formed by computer implemented systems where a computer system in conjunction with various other devices such as cameras motion control devices and so forth executes one or more programs to perform the operation s Real time systems often provide execution environments that facilitate deterministic program or algorithm perfor mance where in this context the term deterministic refers to execution of the program i e performance of the algo rithm in substantially constant time In other words a deter ministic program may be expected to execute and return a result for any valid input set in substantially the same amount of time The term program may refer to an entire applica tion or may refer to a portion of an application such as a sub routine dynamic linked library or any other set of pro gram instructions executable to perform a function opera tion or task However not all programs that execute on real time sys tems are deterministic In fact most real time programs are not deterministic due to a number of restrictions determinism entails or imposes First and foremost the program s resource needs during execution need to be known a priori Otherwise requests from the system for dynamically allocated resources may be made and resource contention cannot be ruled out This requirement alone removes a large set of algorithms as candidates for deterministic executi
47. it In a preferred embodi ment the process includes operations on two or more dif ferent execution threads as described below As FIG 8 shows in one embodiment a timeout mecha nism may be initiated e g a timer started running in its own thread e g Thread A at time critical priority Once the timer is started this thread may go to sleep thereby allowing other process to run Note that as shown the thread remains asleep until a timeout occurs or fires described below As FIG 8 also shows a timed program execution process may begin executing in a separate thread e g Thread B As indicated by the Set Priority block the priority of the thread is preferably set so that only the timeout mechanism can inter rupt processing In other words as mentioned above the priority level of Thread B is preferably set to just below that of Thread A so that only Thread A can interrupt the processing of Thread B Then as indicate by the Store Resource State block required resource managers may be enabled and their current state stored in case a timeout occurs In other words any resources required by the program may have their respective state information saved so that in the case of a timeout the resources may be reset to this state A rollback state e g a rollback point may then be set so that the program can be interrupted by the timeout mecha nism as indicated by the Set Rollback State block Note that in FIG 8 the poi
48. leep but allowing the program to be interrupted by the timeout mechanism when the timeout mechanism wakes up Running at time critical priority may beimportant in that otherwisethe program can be interrupted by another process running on the system Likewise the program preferably cannot go to sleep or another process will take over FIG 6A Method for Time Bounded Program Execution FIG 6A is a high level flowchart of a method for time bounded program execution according to one embodiment It should be noted that in various embodiments some of the steps may be performed concurrently in a different order than shown or may be omitted Additional steps may also be performed as desired As FIG 6A shows in 602 a timeout condition may be set in a first process e g a first thread For example a timeout event may be set such that the event will fire when a specified amount of time has elapsed In 604 execution ofa program may be initiated in a second process e g a second thread It should be noted that in other embodiments the second process may include two or more execution threads or processes e g a plurality of second threads Note that in some embodiments execution of the program may include execution of a plurality of programs For example in one embodiment the program may include one or more sub programs i e the program may be a set of programs In 606 during execution of the program the first process
49. lustrated in the Normal Execution Path block Note also that the execution path for the case when no timeout occurs is shown as a thin solid line proceeding through the Normal Execution Path block to the Exit Code block Thus the program Thread B may regain control of the processor but continue processing from a previous execution point As shown the method again checks whether roll back has occurred which in this example is true because the timeout has occurred The method may then restore the state of resources to reflect the resource state prior to running the program indicated by the Restore Resource State block Finally the program may exit e g with an error timeout condition As mentioned above with reference to FIG 7 the manage ment ofresources i e the Store Resource State block and the Restore Resource State block may not be required by all programs and so may be considered optional steps In one embodiment the state of the resources may simply be a valid invalid condition where storing the state insures the resources are valid and the restoring of the state invalidates the resources However in a preferred embodiment the method may actually maintain valid resources so that they are never in an invalid unusable state In one embodiment several rollback states e g rollback points may be established during the program processing to insure safe exiting in case a timeout occurs For example in one embodiment
50. may be associated with a graphical program In this instance various mechanisms may be used to connect GUI Elements in the GUI with nodes in the graphical program For example when Input Controls and Output Indicators are cre ated in the GUI corresponding nodes e g terminals may be automatically created in the graphical program or block dia gram Alternatively the user can place terminal nodes in the block diagram which may cause the display of corresponding GUI Elements front panel objects in the GUI either at edit time or later at run time As another example the GUI may comprise GUI Elements embedded in the block diagram por tion of the graphical program US 7 559 060 B2 9 Front Panel A Graphical User Interface that includes input controls and output indicators and which enables a user to interactively control or manipulate the input being pro videdto a program and view output ofthe program whilethe program is executing front panel is a type of GUI A front panel may be associated with a graphical program as described above In an instrumentation application the front panel can be analogized to the front panel of an instrument In an industrial automation application the front panel can be analogized to the MMI Man Machine Interface of a device The user may adjust the controls on the front panel to affect the input and view the output on the respective indicators Graphical User Interface Element an element o
51. may determine if the timeout condition has occurred and as indicated in 607 if the timeout condition has not occurred then the program may complete and exit normally as shown in 608 If the timeout condition does occur then in 610 the first process may restore the program to a pre defined state in the program referred to as the rollback state as noted above As noted above in a preferred embodiment the rollback state includes a rollback point in the program from which the program may exit normally e g with a timeout condition Once the program has been restored to the pre defined state e g to the rollback state then in 612 the second cess may execute the program from the rollback state with the error condition In other words the second process e g thread may resume execution of the program from the roll US 7 559 060 B2 17 back state In a preferred embodiment the program may resume execution from the rollback point Finally in 614 the program may exit in the second process in response to the timeout condition e g with an error code indicating that program execution was interrupted In other words the program did not complete execution before the timeout occurred and so the program execution may be inter rupted and reset for subsequent execution It should be noted that in preferred embodiments the method of FIG 6A is performed iteratively where for example each time bounded program execution
52. mprises ifthe timeout event has occurred storing an indication ofa timeout condition and wherein the timed program execution process performing a time bounded execution of the program comprises performing a through e if the timeout condition is not indicated 6 The memory medium of claim 2 wherein the program instructions are further executable to iteratively perform setting a timeout event the timed program execution process performing a time bounded execution of the program and disabling the timeout event 7 The memory medium of claim 2 wherein the timeout process executes at a first priority level and wherein the program instructions are further executable to perform setting an execution priority level of the timed program execution process to a second priority level wherein the second priority level is below the first priority level 8 The memory medium of claim 7 wherein said perform ing a time bounded execution of the program further com prises storing an original execution priority level of the timed program execution process prior to said setting the execution priority level of the timed program execution process and wherein e further comprises restoring the execution priority level ofthe timed program execution process to the original execution priority level 9 The memory medium of claim 2 wherein said initiating the timeout process comprises acquiring one or more resources for the t
53. n a real time system to facilitate appropriate time critical behavior and to guarantee special control over resources at run time While this approach is may be more difficult to design and implement than that described above it may result in minimal jitter during execution on any target and avoids intrusive changes to complex programs or algorithms Foundation of the Timed Environment mechanism enforcing the time limit preferably satis fies the following requirements 1 It preferably times events at significantly high resolution preferably microseconds to support the required jitter response for a program US 7 559 060 B2 15 2 It preferably runs at a process priority allowing itto react immediately when a time has expired 3 It is preferably capable of stopping program execution at any point along the program s execution path For example the current timeout mechanism in National Instruments Corporation s LabVIEW RT uses the high reso lution timer capabilities provided on the Pentium III class Intel processors and above but is not limited to this mecha nism Since LabVIEW RT supports time critical execution threads the mechanism runs at time critical highest level priority so that nothing prevents it from reacting to a timeout condition substantially immediately The capability or means to stop the program execution is described in more detail below In a preferred embodiment two or more threads or
54. n thread In one embodiment initiat ing the timeout process may be performed by the timed pro gram execution process In 626 a timeout event may be set Note that the timeout event may be based on a timer a signal from an external process and or any other type of event For example a control process or sensor on a conveyor belt or assembly line may send a signal indicating that a next item has arrived and so indicate that the time period for processing the current item is over and that the time period for processing the next item is to begin In 628 the timed program execution process may perform a time bounded execution of the program or a plurality of programs In one embodiment the execution of the program may be performed at a second priority level where the second priority level is below the first priority level In other words the process that executes the program preferably operates at a priority level below that of the timeout process so that the timeout process can reliably preempt the execution process as necessary preferred embodiment of 628 is described below with reference to FIG 6C As noted above in one embodiment the method may execute a plurality of programs For example as FIG 6B indicates the time bounded program execution may be per formed in an iterative manner where at each iteration a respective program is executed In 630 the timeout event may be disabled and in 632 the timeout process may be
55. ner 2 means for initiating a timeout process wherein the tim eout process is configured to preempt the execution pro cess to interrupt execution of the program 3 means for setting a timeout event wherein the timeout event is an event indicating a timeout condition for the program 4 means for the timed program execution process per forming a time bounded execution ofthe program com prising a means for determining and storing a rollback state for the program b means for executing the program ifthe timeout event has not occurred wherein during said executing if the timeout event occurs C the timeout process setting the timed program execu tion process to the rollback state and disabling the timeout event and d the timed program execution process resuming executing the program based on the rollback state with a timeout condition in preparation to perform a program exit procedure and means for performing the program exit procedure to terminate execution of the program 5 means for disabling the timeout event 6 means for terminating the timeout process and 7 means for terminating the timed program execution process
56. nt in the process just after the rollback state has been determined is marked with an asterisk and is referred to in subsequent steps below check may then be made as to whether a rollback has occurred i e whethera timeout has occurred as indicated by the Rolled back decision block As shown in this example the initial timeout check is false 1 a rollback has not yet occurred and the program begins normal processing indi cated by the thick solid line beginning at the far left of the Normal Execution Path block In other words a timeout has not occurred and so the program begins execution As also indicated in this example during program execu tion the timeout fires waking up Thread A and the following preferably occurs Thread A the timeout mechanism may take control of the processor because it has a higher process priority set in the Set Priority block described above than Thread B The tim eout mechanism may update Thread B s execution state to 20 25 30 35 40 45 50 55 60 65 22 restart processing from the location at which the rollback point was established denoted by the asterisk in FIG 8 andthetimeout mechanism may be reset to await another start operation Note that in FIG 8 bold solid arrows denote the execution path before the timeout occurs and bold dashed arrows denote the execution path after the timeout occurs where as shown the timeout transition is il
57. of various types as desired The network 84 can also be any of various types includinga LAN local area network WAN wide area network the Internet or an Intranet among others The computer systems 82 and 90 may execute a program in a distributed fashion For example computer 82 may execute a first portion of the program and computer system 90 may execute a second portion of the program As another example computer 82 may display the graphical user interface of a program and computer system 90 may execute the remainder ofthe program In one embodiment the graphical user interface of the program may be displayed on a display device of the com puter system 82 and the program may execute on a device 190 connected to the computer system 82 The device 190 may include a programmable hardware element and or may include a processor and memory medium which may execute a real time operating system In one embodiment the pro gram may be downloaded and executed on the device 190 For example an application development environment with which the program is associated may provide support for downloading a program for execution on the device in a real time system Exemplary Systems Embodiments of the present invention may be involved with performing test and or measurement functions control ling and or modeling instrumentation or industrial automa tion hardware modeling and simulation functions e g mod eling or simulating a device or
58. on As noted above another restriction imposed by determinism is that program execution should complete in substantially the same amount of time for all valid inputs This is a significant hurdle to overcome for input domains that are multi dimensional because the sizes and number ofthe dimensions influence the execution time of the program These factors force most deterministic algorithms to be iterative in nature and may also restrict processing to small data sets or usually a single data point resulting in what are referred to as point by point algorithms Because determinism generally imposes severe restric tions on program design and resource usage it is generally impractical or impossible for most complex programs or algorithms to be converted to a form that executes determin istically For example in the field of vision algorithms such as used in machine vision applications virtually all programs operate on images containing two distinct dimensions of data that are spatially related This interrelationship between 20 25 30 35 40 45 50 55 60 65 2 dimensions makes the transition to an iterative form expen sive in resource usage or computationally intensive For example consider blob analysis programs or algorithms designed to determine connected collections of pixels blobs having the same pixel value While these algorithms iterate through the image sequentially their execution time and stor ag
59. on a computer and use execute the program on that computer or deploy the program to a target device for remote execution on the target device that is remotely located from the computer and coupled to the computer through a network Software programs which perform data acquisition analy sis and or presentation e g for measurement instrumenta tion control industrial automation modeling or simulation such as in the applications shown in FIGS 2A and 2B may be referred to as virtual instruments In one embodiment the programs described herein may be graphical programs such asthose developed in the LabVIEW graphical program devel opment environment Other graphical programs and graphi cal program development environments are also contem plated US 7 559 060 B2 13 FIG 4 Machine Vision System for Automated Manufactur ing FIG 4 illustrates a machine vision system or image acqui sition system which is an example of one application of the present invention The time bounded program execution techniques described herein may be used in various types of machine vision or motion control applications For example the computer 102 may be embodied in various form factors and or architectures e g a robot or embedded device among others It is also noted that the time bounded program execu tion techniques described herein may be performed in any of various manners either in software programmable logic or hardware or a
60. ormed first and or may include the releasing In another embodiment initiating the timeout process may further include enabling each of the one or more resource managers and terminating the timeout process further may include disabling each of the one or more resource managers Note that the resources may include any type of resource used by the program and or by the timed program execution process and or by the timeout process For example in one embodiment the one or more resources include one or more memory pools for memory allocations during the time bounded execution of the program In one embodiment prior to determining the rollback state e g the rollback point in the program a respective resource state for each of the one or more resources may be stored and each oftheone or more resource managers may be enabled In this embodiment performing the program exit procedure may include if the timeout event has occurred restoring the respective resource state for each of the one or more resources and disabling each of the one or more resource managers Enabling and Disabling the Rollback During program execution there may be some program states that are unstable e g during certain system calls or processes and during which it may not be safe to perform a rollback For example interrupting a memory allocation may leave the resource manager in an unknown state Thus in one embodiment the rollback mechanism may have a dis
61. other concurrent process mechanisms may be used to implement time bounded program execution also described below In a real time system typically only one time critical pro cess can run at a time To maintain control ofthe processor s a time critical process generally avoids going to sleep or requesting resources from the system In a multi threaded real time system such as LabVIEW RT the timeout mecha nism preferably runs at time critical priority in its own thread In one embodiment when a time limit is started the mecha nism may start an event lasting for the time requested allow ing other processes to run In one embodiment this is a microsecond event wrapper as is used in some operating systems This event may be set by an external signal such as an interrupt which may be invoked by a timer by an external signal etc When the event is triggered the timeout mecha nism may acquire control of the processor from the program s change the state of the thread in which the inter rupted program was executing to a stop state and go idle relinquishing control of the processor to the program s thread The program may then continue from a different execution point that facilitates exiting the operation quickly with a timeout error This altering ofexecution points by thetimeout mechanism along with the need to run at time critical may require the programs to use special resource management tools to avoid requesting resources during
62. out error within a specified time In other words time bounded execution does not require the program to complete the computation in the time allotted With the proper timing environment almost any complex program or algorithm can adhere to a time limit while avoiding substantial program or algorithm changes Supporting Time Bounded Execution One method for facilitating time bounded execution requires every program to repeatedly check against a time limit via a recognized timer and to exit when the time limit is reached While this method uses simple timing components every program must typically be altered to be aware of the time limit by adding timing checks throughout the program code The placement of these checks may be difficult to determine and the checks themselves will typically alter the timing behavior of the program In addition the jitter based on these time checks may vary dramatically from system to system because the execution of the code between time checks may vary substantially A second approach to time bounded program execution involves creating or establishing a timed program execution environment in which programs are unaware of the timing mechanism For this approach three primary components may be needed a mechanism capable of enforcing a time limit resource management tools that avoid system requests during timed execution and time aware program interfaces and utilities These components may be deployed o
63. ow catch model supported in programming but with some very impor 20 25 30 35 40 45 50 55 60 65 16 tant differences First whereas in the exception is typi cally caught in the same thread from which it is thrown in the approach of the present invention the exception is caught in a different thread from where it was generated Because of this the execution stack cannot be used to cleanup e g release or de allocate resources used by the program Herein lies another requirement for resource managers during timed execution If all intermediate resources used by the program are managed specially the state of system resources may always be valid even when rollbacks occur support timed execution programs are preferably aware of the timeout mechanism and resource managers and use them accordingly For example the determination of at least one rollback point as part of the rollback state is generally required at the start of a program so that the program can be interrupted during execution Once a rollback occurs the program preferably avoids system resource requests by using resource managers which may be enabled before the first rollback point the rollback state is established From an execution standpoint the program may typically need to run ata priority just below that ofthe timeout mechanism allow ing the program to run at time critical priority while the timeout mechanism is as
64. product being developed or tested data analysis such as numerical analysis etc Exem plary test applications where the graphical program may be used include hardware in the loop testing and rapid control prototyping among others However it is noted that the present invention can be used for a plethora of applications and is not limited to the above applications In other words applications discussed in the present description are exemplary only and the present inven tion may be used in any of various types of systems Thus the system and method of the present invention 15 operable to be used in any of various types of applications including the US 7 559 060 B2 11 control of other types of devices such as multimedia devices video devices audio devices telephony devices Internet devices etc as well as general purpose software applications such as word processing spreadsheets network control net work monitoring financial applications games etc FIG 2A illustrates an exemplary instrumentation control system 100 which may implement embodiments ofthe inven tion The system 100 comprises a host computer 82 which connects to one or more instruments The host computer 82 may comprise a CPU a display screen memory and one or more input devices such as a mouse or keyboard as shown The computer 82 may operate with the one or more instru ments to analyze measure or control a unit under test UUT or process 150 The on
65. ram FIG 5 is a block diagram representing one embodiment of the computer system 82 and or 90 illustrated in FIGS 1A and 1B or computer system 82 shown in FIGS 2A or 2B It is noted that any type of computer system configuration or architecture can be used as desired and FIG 5 illustrates a representative PC embodiment It is also noted that the com puter system may be a general purpose computer system a computer implemented on a card installed in a chassis or other types of embodiments Elements of a computer not necessary to understand the present description have been omitted for simplicity The computer may include at least one central processing unit or CPU processor 160 which is coupled to a processor or host bus 162 The CPU 160 may be any of various types including an x86 processor e g a Pentium class a PowerPC processor a CPU from the SPARC family of RISC proces sors as well as others A memory medium typically com prising RAM and referred to as main memory 166 is coupled to the host bus 162 by means of memory controller 164 The main memory 166 may store software instructions which are operable to execute a program in a time bounded manner and may also store the program The main memory may also store operating system software as well as other software for operation of the computer system The host bus 162 may be coupled to an expansion or input output bus 170 by means of a bus controller 168 or bus bridge logic
66. ram may exit with an error code indicating the timeout condition as described above As noted above in one embodiment the method may include iteratively performing time bounded execution of a plurality of programs For example in one embodiment iteratively performing the time bounded execution of a plu rality of programs may include performing the method of FIG 6C for each ofthe plurality of programs In one embodiment performing the program exit proce dure may also include if the timeout event has occurred storing an indication of a timeout condition where the timed program execution process performing a time bounded execution ofthe program includes performing the method of FIG 6C for each program only if the timeout condition is not indicated US 7 559 060 B2 19 Thus in a preferred embodiment each of the methods described herein may be performed in an iterative manner where each program or each of a set of programs is per formed as described above for each of a plurality of items processes or events such as for example items on an assem bly line or conveyor belt Inan embodiment where the program includes one or more sub programs or where the program comprises a set of pro grams executing the program in 636 may include performing steps 634 through 640 for each of the one or more sub programs or for each of the set of programs In other words the priority level set in 632 may apply to each of the sub prog
67. rams or the set of programs In one embodiment setting the execution priority level of the timed program execution process may include storing an original execution priority level of the timed program execu tion process prior to setting the execution priority level ofthe timed program execution process In this embodiment per forming the program exit procedure may also include restor ing the execution priority level of the timed program execu tion process to the original execution priority level In one embodiment initiating the timeout process may include acquiring one or more resources for the time bounded execution of the program and initializing one or more resource managers for the one or more resources Note that in some embodiments the acquiring one or more resources may beperformed before the initializing the one or more resources managers while in other embodiments the initializing the one or more resources managers may be performed first and or may include the acquiring Terminating the timeout process may then include releasing the one or more resources for the time bounded execution of the program and un ini tializing the one or more resource managers for the one or more resources Note also that in some embodiments the releasing one or more resources may be performed before the un initializing the one or more resources managers while in other embodiments the un initializing the one or more resources managers may be perf
68. s programs that have been compiled to machine language scripts and other types of executable software A software program may comprise two or more software pro grams that interoperate in some manner Hardware Configuration Program a program e g a netlist or bit file that can be used to program or configure a programmable hardware element Graphical Program A program comprising a plurality of interconnected nodes or icons wherein the plurality of inter connected nodes or icons visually indicate functionality of the program The following provides examples of various aspects of graphical programs The following examples and discussion are not intended to limit the above definition of graphical program but rather provide examples of what the term graphical program encompasses The nodes in a graphical program may be connected in one or more of a data flow control flow and or execution flow format The nodes may also be connected in a signal flow format which is a subset of data flow Exemplary graphical program development environments which may be used to create graphical programs include LabVIEW DasyLab DiaDem and Matrixx SystemBuild from National Instruments Simulink from the MathWorks VEE from Agilent WiT from Coreco Vision Program Man ager from PPT Vision SoftWIRE from Measurement Com puting Sanscript from Northwoods Software Khoros from Khoral Research SnapMaster from HEM Data VisSim from a 5
69. s desired As FIG 6C shows in this embodiment in 632 an execu tion priority level of the timed program execution process may be set to a second priority level where the second prior ity level is below the first priority level as described above In 634 a rollback state in the program may be determined which may include storing an execution state of the timed program execution process at a rollback point In other words the method may include storing state information for the process corresponding to the rollback point such that the process may be rolled back to that point and execution resumed as described below In 636 if the timeout event has not occurred the program may be executed otherwise the method may exit as indi cated in 650 In 638 during program execution if the timeout event occurs the timeout process may restore the execution state of the timed program execution process to the rollback state and disable the timeout event and the timed program execution process may resume executing the program from the rollback state As noted above the rollback state may include a roll back point in the program and so the second process may resume execution of the program from the rollback point Finally in 640 a program exit procedure may be per formed In one embodiment performing the program exit procedure may include clearing the rollback state e g clear ing the rollback point In one embodiment the prog
70. set of programs may be performed in a time bounded manner a plurality of times Finally the timed program execution process may be terminated Thus the timed program execution may be performed for each item in a series of items being processed or analyzed e g items queued for processing on the assembly line or conveyor belt A more detailed embodiment of the timed program execution step follows As described above in one embodiment an execution pri ority level ofthe timed program execution process may be set to a second priority level where the second priority level is below the first priority level rollback state in the program may be determined which may include storing an execution state of the timed program execution process at a rollback point In other words the method may include storing state information for the process corresponding to the rollback point such that the process may be rolled back to that point and execution resumed as described below 0 an 5 20 40 45 50 60 65 4 If the timeout event has not occurred the program may be executed otherwise the method may exit During program execution if the timeout event occurs the timeout process may restore the execution state of the timed program execu tion process to the rollback state and disable the timeout event and the timed program execution process may resume executing the program from the rollback state As noted a
71. sult within time t or exiting with an error in time t dt where dt is the acceptable jitter for the program Memory Medium Any of various types of memory devices or storage devices The term memory medium is intended to include an installation medium e g a CD ROM floppy disks 104 or tape device a computer system memory or random access memory such as DRAM DDR RAM SRAM EDO RAM Rambus RAM etc or a non volatile memory such as a magnetic media e g a hard drive or optical storage The memory medium may comprise other types of memory as well or combinations thereof In addi tion the memory medium may be located in a first computer in which the programs are executed or may be located in a second different computer which connects to the first com puter over a network such as the Internet In the latter US 7 559 060 B2 7 instance the second computer may provide program instruc tions to the first computer for execution The term memory medium may include two or more memory mediums which may reside in different locations e g in different computers that are connected over a network Carrier Medium a memory medium as described above as well as signals such as electrical electromagnetic or digi tal signals conveyed via a communication medium such as a bus network and or a wireless link Programmable Hardware Element includes various types of programmable hardware reconfigurable hardware programmable logi
72. timed execution Any resource request including memory allocations may thus be filled from a pre allocated source once a time limit is active and resources are being requested or the timed execution may be invalid as is the case for deterministic execution Thus for example a memory pool mechanism may be instantiated or allocated prior to starting a time bounded execution to man age memory usage Once the timeout mechanism is enabled a memory pool manager providing deterministic memory operations may service memory requests As noted above when a timeout occurs the timeout mechanism preferably regains control of the processor and changes the execution state of the program it interrupted so that the program may exit with a timeout error when it resumes This may be achieved by restoring the state of the thread in which the program runs to a rollback state where the program can safely exit with a timeout condition or error In one embodiment the rollback state may include a point in the program from which the program may exit gracefully with the timeout condition This point may be referred to as a rollback point and the restoration of the thread state to one of these points may be referred to as a rollback Thus the rollback state preferably includes a rollback point comprising an execution point in the program and an execution state of the timed program execution process at the rollback point This typeof mechanism is similarto the thr
73. ured to preempt the execution process to interrupt execution of the program 3 set a timeout event wherein the timeout event is an event indicating a timeout condition for the program wherein the timed program execution process is configured to 4 perform a time bounded execution of the program wherein in performing the time bounded execution the timed program execution process is configured to a determine and store a rollback state for the program b if the timeout event has not occurred execute the program wherein during said executing if the tim eout event occurs the timeout process is configured to set the timed program execution process to the rollback state and disable the timeout event and d the timed program execution process is configured to resume executing the program based on the rollback state with a timeout condition in preparation to per form a program exit procedure and perform the program exit procedure thereby termi nating execution of the program wherein the program instructions are further executable by the processor to 5 disable the timeout event 6 terminate the timeout process and 7 terminate the timed program execution process 27 A computer system for performing time bounded execution of a program comprising 1 means for initiating a timed program execution process wherein the timed program execution process is config ured to execute a program in a time bounded man
74. w existing code to be time bounded with mini mal changes focusing primarily on resource usage If the code is written using standard coding practices the necessary changes may be localized For example if memory alloca tions are performed via user defined allocate deallocate func tions e g perhaps only wrappers around base allocate deal locate functions then updating those functions to use a resource manager may protect all dynamic allocations requested in the code By eliminating resource requests from the system the deterministic behavior of the code may thus be improved In many cases a wrapper function may be all that is needed to time bound an algorithm especially if all work space buffers are passed as inputs or no internal allocations are needed The traditional way to port an algorithm to a deterministic environment typically involves redesigning the routine to produce results iteratively which is not always efficient or feasible for many complex algorithms For example fast pattern matching algorithms often use a form of sub sampling to characterize a search template Due to the 2 dimensional nature of the problem this type of sampling is inherently non linear making point by point scanning inefficient in his tory accumulation i e for determining possible locales for further inspection Often the samples are normalized to remove variations in lighting making point by point deci US 7 559 060 B2 25 sions
75. w first priority level of timeout process 832 834 determine rollback point in program perform program exit procedure 640 US 7 559 060 B2 Page2 U S PATENT DOCUMENTS 7 181 585 B2 2 2007 Abrashkevich et al 711 170 7 406 688 B2 7 2008 Shibayama etal 718 102 6 230 181 B1 5 2001 Mitchell etal 718 100 7 409 671 B1 8 2008 Meredith et al 717 104 6 269 478 B1 7 2001 Lautenbach Lampe 2003 0140334 1 7 2003 Granston etal 717A25 etal 2 717 127 2004 0015924 Al 1 2004 Hah et al 6 438 749 B1 8 2002 Chamberlain lt 717 174 2004 0064817 Al 4 2004 Shibayama etal 718 104 6 484 276 B1 11 2002 Singh etal 714 41 2004 0158549 Al 8 2004 Matena etal 707 1 6 584 601 B1 6 2003 Kodosky etal 716 4 6 892 331 B2 5 2005 Da Palma etal 714 55 OTHER PUBLICATIONS 7 039 012 B2 5 2006 Nakano et al 370 230 Timing a LabVIEW Operation Technical Note 022 Oct 1992 3 7 043 728 5 2006 Galpin 718 102 pages National Instruments Comondion 7 093 249 B2 8 2006 Melamed et al 718 100 7 178 062 B1 2 2007 Dice 714 38 cited by examiner U S Patent Jul 7 2009 Sheet 1 of 13 US 7 559 060 B2 Computer System 82 Figure 1A US 7 559 060 B2 Sheet 2 of 13 Jul 7 2009 U S Patent g n

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