For large model training and infrastructure engineers

Separate RoCE v2 GID routing mismatches from DeepSpeed ZeRO-3 stage stalls on Scaleway.

Preserve NCCL RoCE Global Identifier (GID) table selections, Priority Flow Control (PFC) indicators, and DeepSpeed parameter partitioning logs when multi-node jobs freeze.

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Replay a resolved Scaleway multi-node DeepSpeed incident

Upload your log file. Review the selected evidence and masking, then run diagnosis. Keep the original log for any follow-up questions.

Before uploading, review cloud data handling and local options.

training_logs.txt

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Upload your log file. Large files are processed in your browser. Only selected evidence is submitted when you run diagnosis.

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Up to 50 diagnoses a day for 30 days. Verify your work email to activate an eligible company evaluation, then replay a resolved incident and compare the evidence and next steps with your team's confirmed cause.

What a useful evaluation should establish

Distinguish underlying RoCE network transport protocol negotiation issues from distributed framework memory deadlocks.

Use Denpex alongside your existing telemetry tools to investigate submitted incident evidence. With monitoring configured on a supported plan, detected failures can trigger alerts and an automatic diagnosis from the captured evidence.

Inside Denpex

See the evidence, not just the claim

Follow the causal chain, inspect the quoted evidence and prepare the next handoff. These actual product captures use founder-account examples and the VS Code extension, with the source identified under each image. Open a capture to inspect it at full size.

Denpex founder-account example: a causal graph connects an Xid 48 ECC event to a rank exit and downstream collective failures, with quoted evidence for each stage. — Live founder-account capture from the bundled NCCL/ECC example. Follow the hardware event, rank exit and downstream symptoms with a supporting log quote at each stage.Inspect original image

Denpex hardware handoff summary asks the operator to capture diagnostic evidence and verify RMA eligibility with the vendor. — Actual hardware handoff summary from the same founder-account example. Capture diagnostic evidence before an approved reset, then confirm RMA eligibility with the vendor.Inspect original image

Denpex historical example says a collective timeout does not establish the initiating rank, cause or failure domain and requests distinguishing evidence before a remedy. — Founder-account example restored from history. The original timeout remains unattributed, and the UI keeps the missing-evidence assessment visible.Inspect original image

Denpex VS Code extension displaying a bundled OOM-before-NCCL example, matched log evidence, verification guidance and an investigation handoff. — Actual VS Code extension capture of the bundled OOM-before-NCCL example. Review matched log evidence, verification guidance and the investigation handoff without leaving the editor.Inspect original image

Failure Signature Triage

Scaleway - Observed Runtime Evidence

Read Scaleway documentation

Incident pattern summary

A 2-node Scaleway H100 job running DeepSpeed ZeRO-3 freezes after step 1 without emitting a Python exception until the 30-minute timeout triggers. The NCCL initialization log shows Rank 0 selected an IPv4-mapped RoCE v1 GID while Rank 8 fell back to TCP socket transport.

Terminal traceback excerpt (Scaleway)

scw-gpu-node-1:512:589 [0] NCCL INFO NET/IB : Using [0]mlx5_0:1/RoCE [1]mlx5_1:1/RoCE ; OOB eno1:10.68.1.12<0>
scw-gpu-node-2:498:544 [8] NCCL WARN NET/IB : Unable to query GID 3 on device mlx5_0, falling back to GID 0
[2026-10-18 14:22:09,112] [WARNING] [stage3.py:1942:step] DeepSpeed ZeRO-3 coordinator waiting on rank 8 in_flight_all_gather

Recommended verification flags

Set these environment flags in your training container or launch script to capture high-resolution collective logs:

NCCL_DEBUG=INFONCCL_IB_GID_INDEX=3NCCL_IB_HCA=mlx5DEEPSPEED_TIMEOUT=15

Diagnostic Scope Boundary

Denpex cannot alter Scaleway top-of-rack switch ECN/PFC configurations or private VPC routing tables. The evaluation pinpoints protocol mismatches between your container environment and the underlying fabric.