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Hao Zhou∗, Xinyu Niu†, Junqi Yuan∗, Lingli Wang∗, Wayne Luk †

Connect On the Fly: Enhancing and Prototyping of Cycle-Reconfigurable Modules. Hao Zhou∗, Xinyu Niu†, Junqi Yuan∗, Lingli Wang∗, Wayne Luk † †Dept. of Computing, Imperial College London, UK

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Hao Zhou∗, Xinyu Niu†, Junqi Yuan∗, Lingli Wang∗, Wayne Luk †

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  1. Connect On the Fly: Enhancing and Prototyping of Cycle-Reconfigurable Modules Hao Zhou∗, Xinyu Niu†, Junqi Yuan∗, Lingli Wang∗, Wayne Luk† †Dept. of Computing, Imperial College London, UK ∗School of Microelectronics, Fudan University, China

  2. Outline • motivation • EURECAarchitecture • Architectureoptimisation • results • summary

  3. Summary of Contributions 1. Reconfiguration strategies for data access patterns • Three categories for dynamic data accesses • Reconfiguration modes: maximise configuration sharing 2. Architecture design space exploration • Multiplexers or permutation network • Optimal EURECA module size 3. Prototype chip layout • Manually developed with SMIC 130-nm technology • Results measured using Cadence tools

  4. Static vs dynamic data access • conditional arithmetic operators • dynamic data access patterns for (i=0; i<n; i+=N) #parallel unroll N for(j=0; j<N; j++){ k=i*N+j; d[k]=a[k+1] * c[k]; } for (i=0; i<n; i+=N) #parallel unrollN for(j=0; j<N; j++){ k=i*N+j; d[k]=a[b[k+1]] * c[k]; } static:easy dynamic:hard

  5. Example: dynamic data access d for (i=0; i<n; i++){ d[k]=a[b[k+1]] * c[k]; } C connectionsfor onedata-path:easy

  6. Example: dynamic data access for (i=0; i<n; i+=N) #parallel unroll N=32 for(j=0; j<32; j++){ k=i*32+j; d[k]=a[b[k+1]] * c[k]; } connectionsfor 32data-paths:hard

  7. Implementation 1: multiplexors • congested routing • 1024-to-1024 bitconnections • unroutable in XC6V-SX475T • expensiveusermultiplexers d 32outputports,each32-bitwide

  8. EURECA module: execution flow Initialconfiguration CDN: Configuration Distribution Network Initialconfiguration

  9. EURECA module: execution flow CG: Configuration Generator Data-paths CG InitialConnections

  10. Run-time reconfiguration flow CG Runtimeconfiguration InitialConnections

  11. Run-time reconfiguration flow CG Initialconfiguration

  12. Run-time reconfiguration flow data-pathdata CG Initialconfiguration memorydata

  13. 1. Optimising Data Access Patterns • Static(a): accesses with fixed strides • Dynamic size(b): linear accesses with variable vector size • Dynamic offset(c): vector access with dynamic offsets • Random(d): each access with a dynamic offset

  14. Dynamic FIFOs • Dynamic sizeDynamicFIFOs:BRAMsorganisedasFIFOs • AsingleconfigurationissharedbyallruntimereconfigurableconnectionsinaEURECAmodule • EnablesignalstoFIFOsaredynamicallyconnectedtocorrespondingFIFOports

  15. Dynamic cache • Dynamic offsetDynamiccache:BRAMsassharedcache • Singleconfigurationsharedbyallruntimereconfigurableconnections • InputaddresstoBRAMsaredynamicallyconnected

  16. Dynamic shared cache • RandomDynamicsharedcache:accessconflicts • Accessconflictshappenwhen2ormoredata-pathstrytoaccessthesameportatthesametime:thelowertwodata-pathsinthefigure • Eachreconfigurableconnectionhasaseparateconfiguration • Conflictedports(thelowestdata-path)aredisabledbyscheduler

  17. 2. Optimising Connection Network • Multiplexersorpermutationnetwork? • Threeparameterstoevaluate: • Numberofpinstosupportruntimereconfiguration • Siliconareatoimplementthenetwork • Logicrequiredtogenerateruntimeconfigurationsforthenetwork

  18. Connection Network • Multiplexersorpermutationnetwork? • Multiplexersareselectedasconfigurationscanbeshared • Toreconfigureapermutationnetworkwithinasinglecycletakesanunacceptableamountofpinsandconfigurationgenerationlogic

  19. Architecture Efficiency • Architectureefficiencyisevaluatedwiththeareasavedbyruntimereconfiguration,multipliedbyoverallareaoverhead Original chip area Original application resource usage Runtime reconfigurable application resource usage EURECA chip area

  20. EURECAOptimisation • Connectionnetwork:multiplexersorpermutationnetwork • Memorygroupsize:thenumberofBRAMblocksconnectedtoasingleEURECAmodule • Circuit models for application area reduction and module area • Small memory group size: small reductions in design area • Large memory group size: large module area overhead • Efficiencyreachesmaximumat32BRAMs, supported by circuit models

  21. 3. EURECAPrototype • PrototypelayoutdevelopedwithSMIC130-nmtechnology • Classicisland-styleFPGAarchitectureadapted • SmallFPGAsizeduetotape-outbudget • AsingleEURECAmoduleaddedtoonecolumnofBRAMs(8) • PrototypelayoutdevelopedwithSMIC130-nmtechnology • AEURECAmoduleisthesameareaas2.72CLBcolumns • AEURECAmodulebrings1.15nsdelay(typicalcircuitcriticalpathdelayonthisarchitecture20-40ns)

  22. EURECAPrototype

  23. Application 1: Large-scale Sorting • Large-scalesorting:dynamicFIFOs • Ateachcycle,thereareunknownamountofvaluescommittedfromeachFIFO • Thestartingaddresschangesfromcycletocycle

  24. Application 2: Memcached • Memcached:dynamiccache • Avectordatapointedbyadynamicpointerisreadeachcycle • Theaddresschangesfromcycletocycle

  25. Application 3: SpMV • SpMV:dynamicsharedcache • Accessedlocationsinthevectordependsonthepostionofnon-zerosinthesparsematrix • Eachvectoraccessisrandom • Aschedulermoduletoonlyenableoneruntimereconfigurationforamemoryport

  26. Experimental Setup • Targetchip • PrototypeEURECAchip • Area,delaymeasuredfromCadencesimulationresults • synthesisenvironment • Design Compiler (DC) for circuit synthesis • ABC for mapping • A graph matching algorithm for packing • Simulated annealing algorithm for placement • Path-finder for routing

  27. ApplicationPerformance • Threeimplementationsdevelopedforeachapplication • StaticdesignuseLUTstosupportalldynamicdataaccesses • EURECAsupportsdynamicaccesseswithoriginalarchitecture • Dynamicusestheoptimisedarchitecture,supportmaximumconfigurationsharing

  28. ApplicationPerformance • Threeimplementationsdevelopedforeachapplication • Upto11.2timesarea-delayreductionscomparedwithstaticdesign • Upto1.39timesarea-delayreductioncomparedwithoriginalEURECAarchitecture

  29. ApplicationPerformance • Area-delayreductionsgrowslinearlyasthenumberofBRAMsconnectedtoaEURECAmodulegrows • Areareductionincreasesto16for32BRAMs

  30. Current and future work • EURECAfull-stackcompiler • EURECAprogrammingmodels • operationmapping • dataaccessmapping • many-regioncommunication • EURECAsimulatorforarchitectureoptimisation • AutomaticallyexploredesignspacewithgeneratedarchitecturefilesandVerilogmodules

  31. Summary: EURECA • Routing challenge: dynamic data access applications • Threedataaccesspatterns • Optimisedreconfigurationstrategies • Designspaceexplorationandprototypelayout • Experimentalresults: prototypelayout+synthesistool • smallareaanddelayoverhead • Applicationperformance • upto1/11.2xarea-delayproductcomparedwithstaticarchitecture • upto1/1.39xarea-delayproductcomparedwithinitialarchitecture

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