Tutorial for the SPARK Parallelizing High
Contents
1. sh where OS is the operating system for which you downloaded the distribution and Version is the Spark version To begin with source the spark setup scr script as follows source spark setup csh if you are using csh tcsh shell spark setup sh if you are using sh bash shell For the Windows distribution if you are using Spark under CYGWIN or MSYS MINGW then you can source the spark setup sh file else for native Windows you can run the batch file spark setup bat The spark setup script sets up the path to the Spark executable along with some environment variables and some default include paths required by Spark The include directory contains standard C include files such as stdio h et cetera that are included by some input applications including our tutorial However note that for the Windows distribution these include files are not useful If you do want to include system files such as stdio h et cetera please specify the path to these files using the environment variable SPARK_INCLUDES or using the command line flag I path to include The directory tutorial contains the Spark tutorial The contents of this directory are tutorial mpeg_play synops README txt README win32 txt The directory mpeg_play contains the Berkeley MPEG player distribution We will next demonstrate how to synthesize the motion estimation algorithm from this MPEG playe2. 1 Reporting Bugs The Spark distribution comes with no official bug fixing support or maintenance and we are not obliged to provide any updates or modifications However you may report bugs to spark ics uci edu Subject BUG Brief description of bug 1 2 Acknowledgments The Spark framework was developed by Sumit Gupta with major contributions to the underlying framework by Nick Savoiu Mehrdad Reshadi and Sunwoo Kim also contributed to the code base Professors Rajesh Gupta Nikil Dutt and Alex Nicolau led the Spark project This project was funded by Semiconductor Research Corporation and Intel Incorporated 1 3 Change Log Date Changes 1 12 04 Introduced documentation for the newly introduced Windows version of SPARK Also some additional notes in the VHDL section since output VHDL is now synthesizable by Xilinx XST 09 1 03 First release of document 1 4 Copyright The Spark software is Copyright 2003 2004 The Regents of the University of California All Rights Re served Permission to use copy modify and distribute this software and its documentation for educational research and non profit purposes without fee and without a written agreement is hereby granted provided that the above copyright notice this paragraph and the following three paragraphs appear in all copies Permission to incorporate this software into commercial products or for use in a commercial setting may be obtained by contacti
3. Tutorial for the SPARK Parallelizing High Level Synthesis Framework Version 1 1 Sumit Gupta Center for Embedded Computer Systems University of California at San Diego and Irvine sumitg cecs uci edu http mesl ucsd edu spark Copyright 2003 2004 The Regents of the University of California All Rights Reserved April 14 2004 Contents 1 About this Tutorial 1 1 Reportins Bugs dani e aoe ye a RB ae a 1 2 Acknowledaments 2 044 24 24 44 ea ea ea Per ae Sada Pe adore bacea eae wo Lo Change LOB ha e 2 koe ae ie ks Oe ea ee TAO Bee eee fe a 14 ICOPYEBDE sie asa Ga ee RK oe ee ee a We Oe oe Ge ee we kS Disclaimers tica 06 a aise a eats tia Ae a AD we le e a ah ld ee 2 Downloading and Executing the Spark Tutorial 2 1 Downloading and Setting up the Tutorial ee ee 2 2 Synthesizing the Motion Compensation Algorithm _ o e 2 3 Functional Verification of Output C Generated by Spark o o o ooo o 2 4 Viewing the Graphical Output of Spark o oo 2 5 Logic Synthesis of VHDL Outputof Spark s ss as ew mamas e a ee 2 6 Logic Synthesis using non Synopsys Logic Synthesis Tools o ooo Chapter 1 About this Tutorial This tutorial demonstrates how to use the Spark parallelizing high level synthesis software tool with an example Through the tutorial you will learn how to invoke Spark how to sometimes modify C code to make it synthesizable by Spark 1
4. _Modified dotty dotty output HTG_motionvector_forSpark_c_ComputeBackVector_Modified_sched dotty for the ComputeBackVector function 2 5 Logic Synthesis of VHDL Output of Spark Running Spark on the motion compensation algorithm by sourcing the runTut csh sh script also produces an output VHDL file This VHDL file out put motionvector_forSpark_spark_rtl vhd can be synthesized by Synopsys Design Compiler Change directory to tutorial synops The contents of the synops directory are as follows synops dbs reports scripts src The runTut csh sh script copies the VHDL file out put motionvector_forS park_spark_rtl vhd to the src di rectory here The scripts directory contains the Synopsys synthesis script motionvector_forS park_spark_rtl scr This script can be used for Design Compiler as follows dc_shell f motionvector_forSpark_spark_rtl scr gt dc_out log This script synthesizes the VHDL file and stores the generated reports in the synops reports directory and the generated database files in the synops dbs directory We have set the execution time of the multiplier as 2 cycles in the hardware description file distributed with the Spark tutorial You can alter this cycle time in the de fault spark file that is in the mpeg_play directory under the section titled Resources More information on the format of the de fault spark file is given in the user manual 2 6 Logic Synthe
5. e executable mpeg_play fors park O out put motionvector_forS park_sparkout c The C output file for the motion compensation algorithm produced by Spark after scheduling synthesis This produces the executable mpeg_play afters park You can now test that the three executables work and produce the same results by playing the MPEG video file smoker mpg provided with the tutorial This can be done as follows mpeg_play orig smoker mpg mpeg_play forspark smoker mpg mpeg_play afterspark smoker mpg In this way we can do functional verification of the output C generated by Spark with the input C This gives us some confidence that at least the transformations applied by Spark have not changed the functionality of the application 2 4 Viewing the Graphical Output of Spark Spark produces output graphs for each function in the C input file before and after scheduling The format that Spark uses for the output graphs is that of AT amp Ts Graphviz tool 3 See the Spark User Manual for more details on the output graphs generated You can view the graphs for the input and output scheduled motionvector_forSpark c file by running the following commands dotty output HTG_motionvector_forSpark_c_ComputeForwVector_Modified dotty dotty output HTG_motionvector_forSpark_c_ComputeForwVector_Modified_sched dotty for the ComputeForwVector function dotty output HTG_motionvector_forSpark_c_ComputeBackVector
6. esources allocated to schedule the design resource library The Priority rules file contains the synthesis scripts that control the transformations applied to the design description Detailed information about these files is given in the Spark user manual 2 3 Functional Verification of Output C Generated by Spark Besides RTL VHDL Spark also generates a behavioral C file that corresponds to the transformed and scheduled design Clearly this C file does not have any of the timing clock boundary and structural information but it does have the code transformed by the optimizations applied by Spark Note that This functional verification is not done by the Windows distribution of Spark This is because the mpeg_play MPEG player uses X11 libraries and include files for executing It is thus not portable to Windows as far as we know Users of the Windows distribution can skip the rest of this section The runTut csh sh does functional verification using the output C code against the input C code by calling three targets from the Makefile of mpeg_play These calls to make produce three executables of the mpeg_play distribution for the following three motion estimation files O motionvector c Original motion compensation algorithm shipped with the Berkeley mpeg_play software This produces the executable mpeg_play orig O motionvector_forSpark c motion compensation algorithm modified to make it synthesizable by Spark This produces th
7. file by invoking the following command spark m hli hcs hcp hdc hs hcc hvf hb hec motionvector_forSpark c Note that For the windows distribution the motionvector_forSpark c is modified as motionvector_forS park_win32 c This is to remove include of system files such as stdio h For the rest of this tutorial whenever motionvector_forSpark c is used it refers to the file motionvector_forS park_win32 c in the Windows distribution This command does loop invariant code motion hli common sub expression elimination hcs copy propa gation hcp dead code elimination hdc scheduling hs output C code generation hcc output RTL VHDL code generation hvf resource binding hb and counts the execution cycles hec Invoking Spark with these command line flags produces three outputs a graphical outputs corresponding to Hierarchical Task Graphs HTGs Control Flow Graphs CFGs and Data Flow Graphs DFG b C corre sponding to the scheduled design and c VHDL corresponding to the design after scheduling resource binding and control synthesis To schedule bind perform control synthesis and generate output VHDL Spark reads two other files besides the motionvector_forS park c file These are the de fault spark and the Priority rules files in the mpeg_play directory The de fault spark file is a hardware description file that contains information on timing range of the various data types and the list of r
8. ng Technology Transfer Office 9500 Gilman Drive Mail Code 0910 University of California La Jolla CA 92093 0910 858 534 5815 invent ucsd edu 1 5 Disclaimer O The Spark software program and the documentation is copyrighted by the Regents of the University of California The following terms apply to all files associated with the software unless explicitly disclaimed in individual files O The software program and documentation are supplied as is without any accompanying services from The Regents The Regents does not warrant that the operation of the program will be uninterrupted or error free The end user understands that the program was developed for research purposes and is advised not to rely exclusively on the program for any reason O In no event shall the University of California be liable to any party for direct indirect special incidental or consequential damages including lost profits arising out of the use of this software and its documentation even if the University of California has been advised of the possibility of such damage The University of California specifically disclaims any warranties including but not limited to the implied warranties of merchantability and fitness for a particular purpose the software provided hereunder is on an as is basis and the University of California has no obligations to provide maintenance support updates enhancements or modifications Chapter 2 D
9. ownloading and Executing the Spark Tutorial In this chapter we explain how to download setup and execute the tutorial The sample design we have used for this tutorial is the Berkeley MPEG Player 1 The MPEG player is representative of the class of multimedia and image processing applications that the Spark parallelizing high level synthesis framework has been developed for In this tutorial we show how C code downloaded from the Internet can be synthesized using Spark and the resulting VHDL can be synthesized using commercial logic synthesis tools 2 1 Downloading and Setting up the Tutorial The tutorial is part of the Spark distribution that can be found at the Spark website 2 at http mesl ucsd edu spark Choose the appropriate distribution based on the operating system you want to work on The distribution will be named spark OS Version tar gz So let us say you are interested the 1 1 version for the Linux platform you will download the file spark linux 1 1 tar gz For the Windows distribution we ship a ZIP archive named spark win32 Version zip After downloading this file gunzip and untar the file as follows gunzip spark linux 1 1 tar gz tar xvf spark linux 1 1 tar gz OR unzip spark win32 1 1 zip Uncompressing gunzip and untar the distribution will create the following directory structure spark 0S Version bin include tutorial spark setup csh spark setup
10. r The synops directory contains the Synopsys logic synthesis scripts for synthesizing the output VHDL generated by Spark We will come back to this in Section 2 5 2 2 Synthesizing the Motion Compensation Algorithm We choose the Motion Compensation algorithm from the MPEG 1 player for synthesis since this is one of most computationally expensive parts of the decoder In the Berkeley mpeg_play distribution this algorithm can be found in the file motionvector c An overview of synthesis of motion compensation algorithm by Spark is shown in Figure 2 1 In this figure the motion compensation algorithm corresponds to the motionvector c file Before we can synthesize the motionvector c file using Spark we have to check if the C code in this file is syn thesizable We find that the motionvector c file has two functions ComputeForwVector and ComputeBackVector However one of the inputs of the ComputeForwVector and ComputeBackVector functions is a structure VidStream x the_stream These functions then call the ComputeVector function declared as a de fine with the relevant mem bers of the struct VidStream x the_stream Since Spark does not currently support structs see User Manual we split the motionvector c file into two files motionvector_callsSpark c and motionvector_forSpark c As the names suggest the first file calls the second file We create two functions corresponding to the ComputeForwVector and ComputeBackVector functions in the Es
11. sis using non Synopsys Logic Synthesis Tools For logic synthesis using tools from other vendors you can instruct Spark to generate VHDL that is not vendor specific as follows O Set the PrintSynopsysVHDL to false in the OutputVHDLRules section of the default spark This removes references to Synopsys libraries and DesignWare functions from the VHDL code For example library Synopsys DWARE is removed O You will have to explicitly instantiate multi cycle components such as the multiplier and divider if any from the standard cell library of your technology vendor This has to be done in the architecture description of res MUL and res_DIV in the VHDL code Note that in this tutorial we use a two cycle multiplier Also you will have to write synthesis scripts for your logic synthesis vendor Bibliography 1 The berkeley mpeg player http bmrc berkeley edu frame research mpeg mpeg_play html 2 SPARK parallelizing high level synthesis framework website http www cecs uci edu spark 3 AT amp T Research Labs Graphviz Open source graph drawing software http www research att com sw tools graphviz 10
12. timation Algorithm C After RTL Scheduling VHDL Functional Logic Verification Synthesis Figure 2 1 Partitioning of the MPEG player application and synthesis of the motion compensation algorithm by the Spark high level synthesis tool Spark produces both RTL VHDL and behavioral C as output The C can be used for functional verification against the input C and the VHDL can be synthesized using commercial logic synthesis tools motionvector_forS park c file that are synthesizable by Spark We call these functions ComputeForwVector Modified and ComputeBackVector_Modi fied These functions take as input the members of the struct VidStreamxthe_stream that are required by the ComputeVector function The motionvector_callsSpark c file now contains the original ComputeForwVector and ComputeBackVector functions that now call the modified functions with the appropriate inputs taken from the members of the Vid Stream x the_stream struct We can now synthesize the motionvector_forSpark c file by sourcing the script runTut given in the mpeg_play directory as follows source runTut csh for csh tcsh shell runTut sh for sh bash shell runTut bat native Windows batch file This script first checks to see if it can find the Spark binary in the shell path this check is not done in the Windows distribution please make sure Spark is in your path It then runs Spark on the motionvector_forS park c
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