~/talk

When GPUs Make Python Slower: Patterns and Pitfalls

Talkat PyCon US 2025 · 2025-05-16..05-18· [machine-learning, python]
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slides:none on file

GPU acceleration often slows code when fixed costs dominate: moving RAM↔VRAM wipes out gains so regex string search on cuDF is slower for small or high-bandwidth jobs, while dense math like matrix multiplication on GPU is much faster (compute‑bound). Converting rowwise Python loops creates millions of tiny kernels and yields ~1–3% GPU utilization, surprising 3× vs expected 300× speedups. Tools shown: Numba, CuPy, cuDF, cuGraph and Nsight profiling; rules: minimize memory transfers, maximize operational intensity, avoid many small kernels.

AI-written summary · about

  1. 0:00Introduction and goals
  2. 1:23Minimizing memory transfers
  3. 4:28Analyzing GPU suitability
  4. 12:38Operational intensity
  5. 18:43Data format impact
  6. 24:03Avoiding kernel overhead
  7. 28:12Conclusion and Q&A
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