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ALICE TPC Online Tracking on GPU

ALICE TPC Online Tracking on GPU. David Rohr for the ALICE Corporation 25.5.2010 Lisbon. Large Hadron Collider. Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary. ALICE TPC Online Tracking on GPU. The ALICE Experiment. Introduction Tracking Algorithm

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ALICE TPC Online Tracking on GPU

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  1. ALICE TPC Online Tracking on GPU David Rohr forthe ALICE Corporation 25.5.2010 Lisbon

  2. Large HadronCollider Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  3. The ALICE Experiment Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  4. Tracking Clusters Tracks Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  5. Real TPC pp-Event in Online Event Display Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  6. Simulated Heavy Ion Event Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  7. Tracks found in simulatedHeavy Ion Event Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  8. Tracks in simulated Central Heavy Ion Event Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  9. TPC Clusters divitedinto Slices Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  10. The ALICE TPC Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  11. TPC Trackerand Merger Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  12. One ALICE TPC Sector (Trakingisperformedrowbyrow) Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  13. Tracking Algorithm Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  14. Step I: NeighborsFinder (Fit beststraightlines) Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU dx+

  15. Step II: Evolution (Keep coinciding links) Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  16. Step III: TrackletConstruction Green: SeedRed: Extrapolation Clusters closetotheextraplationpointaresearched Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  17. Neighbours Finder on Real Data Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  18. Evolution Step on Real Data Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  19. TrackletConstruction on Real Data Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  20. TrackletSelection on Real Data Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  21. NVIDIA CUDA GPU Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  22. Parallel TrackletConstruction Trackletsareindependentandcanbeprocessedsimultaneously Becauseofdatalocalitythetrackletsareprocessedfor a commonRow Single Instruction Decoder  Either parallel fittingorextrapolation Red: Initial SeedGreen: Extrapolation Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU CurrentRow

  23. Initial GPU Tracker Performance (PeripheralPb-PB) (8 threads on Nehalem CPU with 8 virtual / 4 physicalcores)  Focus on TrackletConstructionwhenoptimizing Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  24. Active GPU Threads forthe First Implementation Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU Active GPU Threads: 19% Colors representTrackletConstructorSteps: Black: Idle Blue: Track Fit Green: Track Extrapolation x-axis: threads y-axis: time

  25. Active GPU Threads using Dynamic Scheduling Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU Active GPU Threads: 62% Colors representTrackletConstructorSteps: Black: Idle Blue: Track Fit Green: Track Extrapolation x-axis: threadsy-axis: time

  26. Pipelining Initialization / Output on CPU, Tracking on GPU and DMA Transfer canoverlap Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU Time

  27. Final Speedup (Central Heavy Ion) (CPU performance was doubledas a sideeffect) Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  28. Final Speedup in Contrastto Event Size (PP Mode: Special variant optimizedforsmallscaleevents) Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU

  29. Tracking Efficiency Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary ALICE TPC Online Tracking on GPU CPU GPU

  30. Summary Introduction Tracking Algorithm NVIDIA CUDA Tracking on GPU Results Summary Twofoldperformanceincrease on CPU 2.5-fold performanceincreasecomparedto CPU Tracking efficiencymatchesthe CPU tracker‘sefficiency A commonsourcecodeensuresmaintainability CPU still availableduringthe GPU tracking ALICE TPC Online Tracking on GPU Perspectiveforthe Future Next NVIDIA GPU generationFermi mayresult in anotherboost Track Merger maybeadaptedtorun on the GPU

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