SWA (Stochastic Weight Averaging) Training
SWA training issues arise from incorrect averaging frequency, learning rate schedule for SWA, or BN update steps.
SWA training issues arise from incorrect averaging frequency, learning rate schedule for SWA, or BN update steps.
What this failure is
SWA (Stochastic Weight Averaging) Training is a Training Stability failure seen during ML training runs. SWA training issues arise from incorrect averaging frequency, learning rate schedule for SWA, or BN update steps. Common tags: Swa, Weight Averaging, Generalization, Bn Update.
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Why it happens (the mechanism)
SWA applied too early in training. BN running statistics not updated for SWA. SWA LR not annealed correctly. SWA averaging includes bad checkpoints. Taken together, these mechanisms explain why the failure is reproducible, why it tends to surface on specific workloads or scales, and why generic mitigation attempts often fall short without addressing the underlying cause.
What you'll observe
- SWA model is worse than the original model
- SWA doesn't improve generalization
- BN statistics are wrong in SWA model
Common symptoms and what they mean
| Symptom | Why it happens |
|---|---|
| SWA model validation accuracy is lower than online model | SWA applied too early in training |
| SWA BN update is missing | BN running statistics not updated for SWA |
| SWA averaging too early or too late | SWA LR not annealed correctly |
Which systems are affected
- SWA training for better generalization
- Vision models with SWA
- Final phase of training with SWA
How to confirm this is the problem
Use this checklist to test the hypothesis against a small reproduction. No single line proves the root cause, so preserve the preceding events and compare one variable at a time.
- ✓Reproduce the failure from a clean checkpoint/seed: the symptom must appear without warm-up state from a previous run.
- ✓Verified signal present: SWA model validation accuracy is lower than online model
- ✓Verified signal present: SWA BN update is missing
- ✓Verified signal present: SWA averaging too early or too late
- ✓A targeted fix from the "How to fix it" section eliminates or substantially reduces the symptom within one validation pass.
The fix and the prevention pattern
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Diagnose this failure in VS Code
Select the traceback or open the failed terminal, then run Denpex locally to see the initiating rank, collateral failures, exact fix, and verification command without uploading the log.
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Root cause
- SWA applied too early in training
- BN running statistics not updated for SWA
- SWA LR not annealed correctly
- SWA averaging includes bad checkpoints
The fix and how to prevent it
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