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Megatron-LM Initialization Failed

Megatron-LM initialization errors prevent large model training from starting due to configuration mismatches.

Quick answer

Megatron-LM initialization errors prevent large model training from starting due to configuration mismatches.

Symptom
RuntimeError: invalid tensor parallel configuration
Root cause
Hidden size not divisible by tensor parallel size. Number of layers not divisible by pipeline parallel size. TP*PP doesn't match world size.
Recommended fix
Set hidden size divisible by TP size
How Denpex helps
Denpex investigates Megatron-LM Initialization Failed using the evidence you provide or your connected workload collects. Earlier rank, host or application evidence is needed to distinguish an initiating failure from a downstream report.
Distributed Training#megatron#init#tensor-parallel#pipeline-parallel#distributed#large-model

What this failure is

Megatron-LM Initialization Failed is a Distributed Training failure seen during ML training runs. Megatron-LM initialization errors prevent large model training from starting due to configuration mismatches. Common tags: Megatron, Init, Tensor Parallel, Pipeline Parallel.

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Why it happens (the mechanism)

Hidden size not divisible by tensor parallel size. Number of layers not divisible by pipeline parallel size. TP*PP doesn't match world size. Sequence length not divisible by TP. 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

  • Megatron training fails at init
  • Tensor parallel setup fails
  • Pipeline parallel pipeline layout invalid

Common symptoms and what they mean

SymptomWhy it happens
Megatron-LM configuration errorHidden size not divisible by tensor parallel size
TP/PP degree mismatch with modelNumber of layers not divisible by pipeline parallel size
RuntimeError: invalid tensor parallel configurationTP*PP doesn't match world size

Which systems are affected

  • Large model training with Megatron-LM
  • New Megatron deployments
  • Configuration changes

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: Megatron-LM configuration error
  • ✓Verified signal present: TP/PP degree mismatch with model
  • ✓Verified signal present: RuntimeError: invalid tensor parallel configuration
  • ✓A targeted fix from the "How to fix it" section eliminates or substantially reduces the symptom within one validation pass.

Root cause

  • Hidden size not divisible by tensor parallel size
  • Number of layers not divisible by pipeline parallel size
  • TP*PP doesn't match world size
  • Sequence length not divisible by TP

The fix and how to prevent it

Searchable error signature

search key
RuntimeError: invalid tensor parallel configuration

Use this text as a lookup key in logs and upstream issue trackers. It is not presented as a captured customer log. Confirm the cause from your own preceding events, versions, configuration and the cited references.

The fix and the prevention pattern

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Diagnose this failure in VS Code

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Don't just read the fix, diagnose your run

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