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fix: Fix DTensor slice crash after PyTorch 2.9 bump #1689

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Merged
terrykong merged 1 commit into from
Jan 2, 2026
+5 −4
Merged

fix: Fix DTensor slice crash after PyTorch 2.9 bump #1689

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9 changes: 5 additions & 4 deletions nemo_rl/algorithms/loss_functions.py
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Original file line number Diff line number Diff line change
Expand Up @@ -922,11 +922,12 @@ def __call__(
if context_parallel_group is None
else torch.distributed.get_world_size(context_parallel_group)
)
logit_slice_idxs = slice(
seq_start // cp_size,
(seq_start + padded_seq_lengths[seq_idx]) // cp_size,
logit_start = seq_start // cp_size
logit_end = (seq_start + padded_seq_lengths[seq_idx]) // cp_size
logit_length = logit_end - logit_start
next_token_logits_slice = next_token_logits.narrow(
1, logit_start, logit_length
)
next_token_logits_slice = next_token_logits[:, logit_slice_idxs, :]

loss, metrics = self.loss_fn(
next_token_logits_slice,
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