Fix backward compatibility in normalization#3
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jlamypoirier
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May 20, 2026
- Add `_sdp_dim`/`_sdp_active` to `LanguageModelLoss.__init__` so GSPO's SDP branch doesn't AttributeError on the first non-test call. - Replace `document_index.max().item()` (and the SDP MAX all-reduce) with `len(kwargs[BlockKwargs.lengths])`: CPU-side, identical across SDP ranks, removes two GPU→CPU syncs per microbatch. - Decorate `fused_gspo_loss_forward_backward` with `@torch.compile` for parity with GRPO. The `num_segments == 1` test case skips on CPU since torch._inductor's CPU codegen mishandles `index_add_` into a size-1 buffer (atomic_add scatter). - Make `divisor` a required arg on `fused_gspo_loss_forward_backward`: the wrapper always overrides it with the global document count, and the previous local-rank default would silently mis-normalize under SDP. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Hopefully this works.