broadcast_coalesced Fails with Cuda failure 1 'invalid argument'
DataParallel model replication fails at the SharedInit step with a CUDA invalid-argument error, often tied to legacy nn.DataParallel inside complex launchers.
DataParallel model replication fails at the SharedInit step with a CUDA invalid-argument error, often tied to legacy nn.
What this failure is
broadcast_coalesced Fails with Cuda failure 1 'invalid argument' is a Communication failure seen during ML training runs. DataParallel model replication fails at the SharedInit step with a CUDA invalid-argument error, often tied to legacy nn.DataParallel inside complex launchers. Common tags: Nccl, Dataparallel, Broadcast Coalesced, Invalid Argument.
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Why it happens (the mechanism)
Nn.DataParallel re-replicates the model and re-inits NCCL state per step. SharedInit fails with an invalid CUDA argument under the launcher's device/visibility setup. Often a CUDA_VISIBLE_DEVICES / context mismatch inside the wrapper. Taken together, these mechanisms explain why the failure is reproducible, why it tends to surface on specific workloads or scales, and why generic mitigation attempts often fall short without addressing the underlying cause.
What you'll observe
- Crash during model replication at the end of an epoch
- Happens inside torch._C._broadcast_coalesced
- Uses nn.DataParallel rather than DDP
Common symptoms and what they mean
| Symptom | Why it happens |
|---|---|
| RuntimeError: NCCL Error 1: unhandled cuda error | nn.DataParallel re-replicates the model and re-inits NCCL state per step |
| NCCL WARN Cuda failure 1 'invalid argument' | SharedInit fails with an invalid CUDA argument under the launcher's device/visibility setup |
| Socket recv failed while polling for opId | Often a CUDA_VISIBLE_DEVICES / context mismatch inside the wrapper |
Which systems are affected
- nn.DataParallel multi-GPU jobs
- HuggingFace Trainer wrapped in Ray remote tasks
- A100 nodes with NVLink, NCCL 2.19.x
How to confirm this is the problem
Use this checklist to test the hypothesis against a small reproduction. No single line proves the root cause, so preserve the preceding events and compare one variable at a time.
- ✓Reproduce the failure from a clean checkpoint/seed: the symptom must appear without warm-up state from a previous run.
- ✓Verified signal present: RuntimeError: NCCL Error 1: unhandled cuda error
- ✓Verified signal present: NCCL WARN Cuda failure 1 'invalid argument'
- ✓Verified signal present: Socket recv failed while polling for opId
- ✓A targeted fix from the "How to fix it" section eliminates or substantially reduces the symptom within one validation pass.
The fix and the prevention pattern
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Install the free VS Code extensionNCCL errors in context
NCCL is where a distributed job reports failure, which is not the same as where it failed. The hub lists every common NCCL error next to what it actually indicates, and the environment variables that tell them apart.
Compare every nccl error side by sideRelated failures to investigate next
Root cause
- nn.DataParallel re-replicates the model and re-inits NCCL state per step
- SharedInit fails with an invalid CUDA argument under the launcher's device/visibility setup
- Often a CUDA_VISIBLE_DEVICES / context mismatch inside the wrapper
The fix and how to prevent it
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