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HeteCCL: Synthesizing Near-Optimal Collective Communication Schedules for Heterogeneous

Talkat NSDI '26 · 2026-05-04..05-06· [machine-learning, distributed-systems]
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name:Jiayi Li
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HeteCCL generates near‑optimal collective schedules by quantizing data into step‑level chunks, modeling topology and link bandwidth precisely, and casting scheduling as a maximum parallel transfer problem on a weighted directed graph solved with SMT formulas and counterexample‑guided inductive synthesis. Implementation synthesizes schedules two orders of magnitude faster than prior synthesizers, achieves up to 2.8×, 4.4×, and 2.6× higher bandwidth versus NCCL, TACCL, and TE‑CCL on 32‑GPU H20/V100 testbeds, and speeds end‑to‑end training by 23%–37%.

AI-written summary · about

  1. 0:00Introduction to HeteCCL
  2. 1:15Limitations of fixed schedules
  3. 2:55Challenges in synthesis
  4. 4:09Impact of heterogeneity
  5. 6:28Pipeline and model issues
  6. 8:00SMT problem formulation
  7. 9:53Chunking abstraction
  8. 10:50Search space reduction
  9. 11:22Inductive synthesis approach
  10. 12:27Evaluation and results
  11. 13:38Conclusion
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