[fix] Enforce param dtype before wrap ddp#992
Merged
Conversation
Contributor
There was a problem hiding this comment.
Code Review
This pull request introduces a _wrap_model_with_ddp function to ensure that fp32 parameter restoration is performed before Distributed Data Parallel (DDP) wrapping, preventing parameter detachment from buffers. It also adds a unit test to verify this sequence. The review feedback suggests addressing a hardcoded path in the test, replacing magic numbers in the bucket size calculation with constants, and removing an unnecessary CUDA stream during DDP initialization to reduce complexity.
The dtype enforcement is no longer needed at these call sites; the model provider now handles fp32 param marking natively. Made-with: Cursor
With enforce_marked_param_dtypes removed, the custom DDP wrapper that ran after fp32 restoration is no longer needed. Revert to letting Megatron's get_model() handle DDP wrapping directly. Also remove the now-obsolete test_model_fp32_wrap_order test. Made-with: Cursor
Zhichenzzz
approved these changes
Apr 20, 2026
yueming-yuan
approved these changes
Apr 21, 2026
DavidBellamy
added a commit
to LLM360/miles
that referenced
this pull request
Apr 21, 2026
…region clusters (#10) * Revert "[BUGFIX] [P2PRDMA] Add rollout post-processing after P2PRDMA weight updates" (radixark#882) * [Fix] fix ci (radixark#894) * Avoid threading for ray getting object (radixark#886) * Add explicit errors for unsupported Megatron profiles (radixark#887) * Add nvfp4 quantizer files (radixark#907) * Bump flash-linear-attention version to 0.4.2 (radixark#892) * [BUGFIX] Invoke "post_process_quantization" by default after weight updating (radixark#890) Co-authored-by: Yueming Yuan <yym022502@gmail.com> * Add heartbeat and id to session server (radixark#866) * fix: adding thin glm5 image to docker build + latest tag sync (radixark#871) * Add consistent hashing routing policy for rollout (radixark#891) Co-authored-by: Yueming Yuan <yueming@Mac.attlocal.net> * [example] add retool v2 example with multi-turn framework interfaces (radixark#654) Co-authored-by: GuanxingLu <gxlu02@gmail.com> Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * Expose rollout-batch-size, n-samples-per-prompt, global-batch-size as CLI args in swe-agent-v2 (radixark#954) Co-authored-by: Shi Dong <shi.dong@radixark.ai> * chore: remove obsolete swe-agent server.py and run-qwen3.sh (radixark#952) Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * Add weight staleness control for fully async rollout (radixark#958) * Fix/pause generation mode (radixark#924) Co-authored-by: Yueming Yuan <yym022502@gmail.com> * [v0.5.10][1] Bump sglang to v0.5.10 (radixark#898) * [v0.5.10][2] Fix apply_chat_template behavior for transformers >=5.0 (radixark#926) Co-authored-by: guapisolo <guapisolo@gmail.com> Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * [v0.5.10][3] Fix processor return_tensors duplicate kwarg for transformers >=5.0 (radixark#927) Co-authored-by: guapisolo <guapisolo@gmail.com> Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * [v0.5.10][4] Fix _no_split_modules set not subscriptable in transformers >=5.0 (radixark#931) * [v0.5.10][5] Disable piecewise cuda graph to avoid NVLS oom (radixark#935) * [v0.5.10][6][FSDP] fix outdated weight update logic in FSDP (radixark#948) Co-authored-by: guapisolo <guapisolo@gmail.com> Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Co-authored-by: maocheng23 <35615230+maocheng23@users.noreply.github.com> Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> * [v0.5.10][7][FSDP] move FSDP to experimental and disable by default (radixark#961) * Add skiplist and more robust calculation on val (radixark#965) * [fix] tiny fix debug rollout only in weight version check (radixark#967) * feat: real cp support with relayout fix for qwen3.5 train/rollout mismatch (radixark#885) * [AMD] Upgrade to sglv0.5.10 (radixark#973) * switch model to actor (radixark#756) * [fix] support general logic to bypass fp32 downcast and fix qwen35 A_log dtype (radixark#975) Co-authored-by: yueming-yuan <yym022502@gmail.com> * fix: populate prefix_cache_info in OpenAI/session rollout path (radixark#960) * Remove prepare_harbor_tasks.py; use harbor-private adapters (radixark#982) * [fix] Skip flush_cache in in_place mode and add fully async example (radixark#974) Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * GLM47 full cmd for async and sync reasoning (radixark#986) Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> * fix: handle non-tool appended messages in TITO incremental tokenization (radixark#949) Co-authored-by: Yanbin Jiang <jybsuper@gmail.com> * [docker] Add sgl-model-gateway install and download .tar.gz assets (radixark#895) * [ci] fix hf rate limit error by caching tokenizer loading (radixark#1014) Co-authored-by: maocheng23 <35615230+maocheng23@users.noreply.github.com> * Use load_generate_function in legacy sglang_rollout path (radixark#1016) * Update CODEOWNERS to add new reviewers (radixark#1021) * Support moe lora for gpt-oss (radixark#798) Co-authored-by: Ethan (Yusheng) Su <yushengsu.thu@gmail.com> * [fix] restore expert_bias to fp32 before bridge weight export (radixark#811) * [chore] drop legacy transformers upgrade pin for glm47-flash and qwen35 (radixark#1018) * [fix] Enforce param dtype before wrap ddp (radixark#992) Co-authored-by: Zhichen Zeng <zczeng@uw.edu> * [upgrade] update Megatron-Bridge source and LoRA CI to megatron e2e tests and (radixark#1023) * [CI] Drop --use-miles-router from R3 tests and add r3 comparasion test between sgl & miles router (radixark#1015) * wandb: raise init_timeout, add retry wrapper, fix shared-mode init for cross-region clusters In online + shared mode, both `init_wandb_primary` and `init_wandb_secondary` make HTTPS round-trips to wandb cloud (login + run create/attach). On high-latency cross-region clusters (e.g. Abu Dhabi MBZUAI ↔ wandb-cloud US-West) with concurrent actor bursts, a single round-trip can exceed the wandb SDK's 90s default `init_timeout` — tearing down the whole run with a silent handshake abort. Observed on RL360 job 1564420, which forced `WANDB_MODE=offline` as a global default ever since (see https://github.com/LLM360/RL360/issues/87). The issue's original diagnosis assumed a local primary↔secondary socket handshake race. That's not how shared mode works — per wandb's own feature PR (wandb/wandb#6882), each writer spawns an independent wandb-core that talks to the cloud directly; aggregation is server-side by run_id. No local socket exists. The failure mode is pure network/latency, not a local readiness race. Changes ------- - Bump `init_timeout` to 300s for primary and secondary Settings. Configurable via `WANDB_INIT_TIMEOUT_SECS` env var for tuning. - Wrap both init paths in a bounded exponential-backoff retry (`_wandb_init_with_retry`) that re-attempts on wandb.errors.CommError and wandb.errors.UsageError. 3 attempts with 5→10→20s backoff by default, tunable via `WANDB_INIT_RETRY_ATTEMPTS` / `WANDB_INIT_RETRY_BACKOFF_SECS`. - Add `x_label` tagging per wandb distributed-training docs: primary gets `rank_<rank>_primary`, secondaries get `rank_<rank>_secondary`. Enables per-rank console-log filtering in the wandb UI. - Drop `reinit=True` from secondary init_kwargs. Shared mode natively supports concurrent writers on a single run; `reinit=True` triggered stale-state warnings on secondary actors without functional benefit. Followups this change enables ----------------------------- - `WANDB_MODE=offline` can be removed from scale.yaml's extra_env default once a pilot run confirms online mode boots cleanly. - The tmux-based `~/bin/wandb-sync-rl360.sh` workaround on David's M2 account becomes obsolete (no more offline-only default). - Near-realtime wandb dashboards replace the ~2-minute-lag offline sync; per-rank system metrics via x_label filtering. --------- Co-authored-by: JD <jaedon.guo@gmail.com> Co-authored-by: Ethan (Yusheng) Su <yushengsu.thu@gmail.com> Co-authored-by: fzyzcjy <5236035+fzyzcjy@users.noreply.github.com> Co-authored-by: Ziang Li <ziangli@umich.edu> Co-authored-by: Zhichen Zeng <zczeng@uw.edu> Co-authored-by: JensenFire <xinji1@microsoft.com> Co-authored-by: Yueming Yuan <yym022502@gmail.com> Co-authored-by: maocheng23 <35615230+maocheng23@users.noreply.github.com> Co-authored-by: Douglas Yang <douglasyang88@gmail.com> Co-authored-by: Yueming Yuan <yueming@Mac.attlocal.net> Co-authored-by: Huapeng Zhou <73010314+PopSoda2002@users.noreply.github.com> Co-authored-by: GuanxingLu <gxlu02@gmail.com> Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com> Co-authored-by: Shi-Dong <Shi-Dong@users.noreply.github.com> Co-authored-by: Shi Dong <shi.dong@radixark.ai> Co-authored-by: Jiajun Li <48857426+guapisolo@users.noreply.github.com> Co-authored-by: guapisolo <guapisolo@gmail.com> Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com> Co-authored-by: Yuzhen Zhou <82826991+zyzshishui@users.noreply.github.com> Co-authored-by: Yanbin Jiang <jybsuper@gmail.com> Co-authored-by: Ying Sheng <sqy1415@gmail.com> Co-authored-by: Yisheng Gong <yishenggong9437@gmail.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Need this. radixark/Megatron-LM#24
Bug behavior
When running
scripts/run-qwen3.5-35B-A3B-mtp-r3.sh, the logprob diff between train and inference (with r3):There is a spike after the first training step.
Root cause
The original fix #975 enforced marked tensors' data type to
fp32, but the timing is not correct.convert_hf_to_torch_dist.pybuilds the model structure withwrap_with_ddp=False. In the real training,miles/backends/megatron_utils/model.pybuild the model structure withwrap_with_ddp=Trueand set up ddp.Originally, we do the fp32 enforcement after
get_model(). But if we callget_model(wrap_with_ddp=True), the ddp will be build in theget_modelfunction with the wrong precisionbf16. Even though we do the fp32 enforcement right after theget_model, it's still useless.This also explain why step 0 is correct but step 1 is wrong. In step 0, we directly load the model weight from the converted ckpt with correct precision. But in step 1, we will do the fwd/bwd and update model weight with
bf16instead offp32and cause such a big numeric diff.Solution
Do the enforcement in Megatron
get_model()function beforewrap_with_ddp. See radixark/Megatron-LM#24Result
After the fix: