Open-Source Zephon Data Loader Integrates TorchTitan With Bit-Identical Training Resumption
josh_wills · x · 2026-10-17
Zephon, a recently open-sourced training data loader, announced integration with PyTorch TorchTitan. Key claim: identical global batches when training resumes on a different GPU count—in a 1B-parameter test, resuming a 16-GPU checkpoint on 8/32/64 GPUs matched every global batch's SHA-256 hash.
Zephon tokenizes, packs, shuffles, and mixes data inside the training job, avoiding a preprocessed corpus copy. Data, tokenizer, seed, mixture, context length, and global batch size must stay unchanged when resuming; lane counts must divide evenly across data-parallel replicas and each optimizer step's batch across lanes.
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