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Alice Weekly Meeting: Software for Hardware Accelerators

→ Europe/Zurich
ALICE GPU Meeting
Zoom Meeting ID
61230224927
Host
David Rohr
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    • 10:00 → 10:20
      Discussion 20m
      Speaker: David Rohr (CERN)

      Color code: (critical, news from this week: blue, news from last week: purple, no news: black)

      Sync reconstruction

       

      Async reconstruction

      • Need to investigate short GPU stall problem.
      • Limiting factor for pp workflow is now the TPC time series, which is to slow and creates backpressure (costs ~20% performance on EPNs). Enabled multi-threading as recommended by Matthias - need to check if it works.
      • Will tune existing 16-core settings, add a SITEARCH for 16core CPU, and 16coreCPU + generic NVIDIA / AMD GPU, like for 8 core.
      • Will retune EPN async workflow for TPC + ITS on GPU on 2025 data.

       

      GPU ROCm / compiler topics:

      • Problem with building ONNXRuntime with MigraphX support.
      • Need to find a way to build ONNXRuntime with support for CUDA and for ROCm.
      • Try to find a better solution for the problem with __device__ inline functions leaking symbols in the host code.
      • Need to check ROCm 7.2 corrtecness.
      • Need to understand deterministic mode issue on AMD Pro 9700 reported by Oliver - Status?

       

      TPC / GPU Processing 

      • WIP: Use alignas() or find a better solution to fix alignment of monte carlo labels: https://its.cern.ch/jira/browse/O2-5314
      • Need to check the problem with ONNX external memory allocator.
      • Next high priority topic: Improvements for cluster sharing and cluster attachment at lower TPC pad rows. PR: https://github.com/AliceO2Group/AliceO2/pull/14542
      • Check for unnecessary f64 instructions in GPU code.
      • PR with changes for qTot-reading / dEdx code, to support >16 bit range for saturated signals: merged

       

      Other topics:

      • Need to bump ONNXRuntime to 1.24, Giulio is checking, needed for ROCm 7.2 - Status?
      • GCC bump - Status?

       

      EPN GPU Topics:

      • 2 nodes with MI50 and MI100 with ALMA 10.2 and newest ROCm available for validation.
    • 10:20 → 10:25
      TPC ML Clustering 5m
      Speaker: Christian Sonnabend (CERN, Heidelberg University (DE))

      Tangent vector application in track seeding

      • Neural network can predict tangent vector to track trajectory -> This can be used in seeding
      • Network predicts sector-local dy/dx and dz/dx => In neighbour finding we can use e.g. y + NN_dydx*dx

       

      Implemented. Draft-PR for discussion: https://github.com/AliceO2Group/AliceO2/pull/15582

      So far reproducing the same number of tracks within 0.5‰. Slow-down due to additional computations: 2.93±0.01 s/TF (NN class + reg, epn000) -> 3.15±0.013 s/TF (NN class + reg + mom vector, epn000). (Default reco is 2.06±0.01 s/TF)

      Need to do MC investigation now.

       

      LHCP proceedings: https://alice-conferences.web.cern.ch/node/70501

      CHEP proceedings: https://alice-conferences.web.cern.ch/node/70535

      ICHEP slides: In preparation

    • 10:25 → 10:30
      GPU Parameter Optimizations 5m
      Speaker: Gabriele Cimador (CERN, Università and INFN Torino)
    • 10:30 → 10:35
      Efficient Data Structures 5m
      Speaker: Dr Oliver Gregor Rietmann (CERN)
       

      NextGenTrigger Task 1.7

      • Supervising a student to work an a CMS clustering algorithm.
      • Gave a presentation about my NGT cluster usage this Friday.

      Implement NGT SoA Code in O2 standalone benchmark

      • Working on this fork of the AliceO2 repo, with a CI pipeline:
        • Running on NGT hardware with 4 different GPUs (Nvidia and AMD)
        • Extended CI-pipline to fail if GPU.out changes
      • Implemented SoA in:
        • SectorTracker
          • GPUTPCBaseTrackParam
          • GPUTPCTrackParam
          • GPUTPCTracklet
          • GPUTPCTrack
      • Writing ACAT Proceedings (deadline extended to end of July)
      • Make better use of SoA to improve performance
      • Next Steps:
        • ...
    • 10:40 → 10:45
      TPC Clusterization / OpenCL / Highly Ionizing Particles 5m
      Speaker: Felix Weiglhofer (CERN)
       

      OpenCL

      No news.

      GPU Servers

      • CI Server: alidist recipe for a simple GPU smoke test done (https://github.com/alisw/alidist/pull/6264)
      • New issue: GPU server had issues with handling Vault secrets (will follow up with Giulio)

      Highly Ionizing Particles

      • vectorized CPU version of tail filter done
        • Tiny differences persist in deterministic mode (~ 1 / 10^7 clusters)...
    • 10:45 → 10:50
      ITS Tracking 5m
      Speakers: Felix Schlepper (CERN, Heidelberg University (DE)), Gabriele Cimador (CERN, Università and INFN Torino), Matteo Concas (CERN)

      Felix: no news. preparing some scripts for Gabriele to validate/tune his vertexing changes

    • 10:50 → 10:55
      System Run Coordination Topics 5m
      Speaker: Ernst Hellbar