Princeton & UPenn propose Recurrent Looped Transformer: 100% parity at 256 bits after training on 40

TheTuringPost · x · 2026-10-17

Princeton and UPenn researchers propose the Recurrent Looped Transformer (RLT), which splits its layers between a parallel causal encoder (building shared KV memory) and a recurrent decoder that carries a running state updated at each token, so computation depth grows with sequence length at fixed per-token cost. Trained on at most 40 bits, RLT generalizes parity to 256 bits with 100% accuracy (baseline Transformer stays at chance), reaches 97% on swap-based permutation tracking at 8x training length (vs <1%), and up to 93% on out-of-range modular arithmetic (vs 33%). Ablations show layer splits between reading and updating matter per task; chunking feedback to every 4 tokens preserves 99% parity but tanks permutation tracking from 100% to 20%.

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