PufferLib 5.0 hits 60M steps/sec single-GPU RL training, solves Breakout in under a second

jsuarez · x · 2026-09-17

PufferLib 5.0 ships alongside an in-depth engineering writeup: up to 60M useful training steps per second on a single GPU, enough to solve Breakout in under a second. Version 4.0's custom CUDA C stack took an 8-month slog; 5.0 polishes the jank off.

Key numbers: throughput scales linearly down to below 100k parameters — 50M sps at 100k params, 10M sps at 1M params, and 1.8M sps at 10M params. The author argues this reverse-direction scaling (small-model efficiency, not the communication-overhead-besieged scaling-up race) is what makes the result striking.

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