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Phantora: Maximizing Code Reuse in Simulation-based Machine Learning...

Talkat NSDI '26 · 2026-05-04..05-06· [machine-learning]
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name:Yongji Wu
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name:Liang Luo
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Phantora runs unmodified ML frameworks inside containerized rank emulators and intercepts CUDA/NCCL calls to forward computation and communication events to a discrete-event simulator, using one real GPU for kernel profiling. It supports Megatron, DeepSpeed and TorchRec out of the box, simulates up to 256 GPUs at roughly one minute per GPU per iteration, and reports 2.9% average error (8.5% max) versus published benchmarks using hybrid simulation and one-GPU profiling.

AI-written summary · about

  1. 0:00Phantora introduction and goals
  2. 1:44Simulation method limitations
  3. 4:53Hybrid simulation code reuse
  4. 6:57Phantora architecture components
  5. 8:21Rollback for past events handling
  6. 10:50Emulating CUDA PyTorch behaviors
  7. 12:13Transparent execution tuning case
  8. 13:39Validation Touch Titan benchmarks
  9. 14:43Future directions challenges
  10. 16:27Conclusion open-source
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