Meta & MIT paper: looping transformer layers beats adding depth at fixed size

rohanpaul_ai · x · 2026-11-02

A new Meta/MIT paper, "How to Loop Your Transformer," systematically studies looping — re-running the same layers multiple times to add depth without extra parameters. Trained from scratch at up to 1B params on 155B tokens (up to 1.07×10²¹ FLOPs, 32 loops), it finds looping the full stack gives the best quality at a fixed parameter budget, while looping a middle block pays off best when training compute is tight. Gains from more loops eventually saturate or reverse; small per-loop low-rank adapters (only +1.1–4.3% params vs +51.4% for doubling depth) help more as loops increase. The paper also fixes Parallel Loop Transformers so loop stages can run concurrently during decoding, removing the linear decoding slowdown.

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