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All-reduce ntokens_seen before logging #1509

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Merged
tianyu-l merged 2 commits into from
Aug 1, 2025
Merged

All-reduce ntokens_seen before logging #1509

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d19395c
All-reduce ntokens_seen before logging
runame Jul 31, 2025
540eab8
Style fix
runame Aug 1, 2025
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10 changes: 10 additions & 0 deletions torchtitan/distributed/utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,16 @@ def dist_max(
)


def dist_sum(
x: torch.Tensor,
mesh: DeviceMesh,
extra_pg: dist.ProcessGroup | None = None,
) -> float:
return _dist_reduce(
x, reduceOp=c10d.ReduceOp.SUM.name, mesh=mesh, extra_pg=extra_pg
)


def dist_mean(
x: torch.Tensor,
mesh: DeviceMesh,
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12 changes: 10 additions & 2 deletions torchtitan/train.py
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Original file line number Diff line number Diff line change
Expand Up @@ -498,15 +498,23 @@ def train_step(
if parallel_dims.dp_cp_enabled:
loss = loss.detach()
ft_pg = self.ft_manager.loss_sync_pg
global_avg_loss, global_max_loss = (
global_avg_loss, global_max_loss, global_ntokens_seen = (
dist_utils.dist_mean(loss, parallel_dims.world_mesh["dp_cp"], ft_pg),
dist_utils.dist_max(loss, parallel_dims.world_mesh["dp_cp"], ft_pg),
dist_utils.dist_sum(
torch.tensor(
self.ntokens_seen, dtype=torch.int64, device=self.device
),
parallel_dims.world_mesh["dp_cp"],
ft_pg,
),
)
else:
global_avg_loss = global_max_loss = loss.detach().item()
global_ntokens_seen = self.ntokens_seen

extra_metrics = {
"n_tokens_seen": self.ntokens_seen,
"n_tokens_seen": global_ntokens_seen,
"lr": lr,
}
self.metrics_processor.log(
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