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Profile and Fix

Don't guess why training is slow — measure it, then fix what the measurement shows.

Key Insight​

The PyTorch profiler records how long each part of a training step takes, so you can see whether the data loader — not the model — is the bottleneck. Common fixes include adding worker processes or enabling pinned memory.

Why This Matters​

Developers routinely guess wrong about where time goes and "optimize" the wrong thing. Profiling first turns tuning from guesswork into a targeted fix — the difference between an idle GPU and a fully-fed one.