Support DSV4 disaggregated launcher

[yueming-yuan]

Summary

• Add DeepSeek V4 launcher resource plumbing for non-colocated training and rollout workers
• Use --rollout-num-nodes to derive actor nodes and rollout GPU counts from --num-nodes and --num-gpus-per-node
• Use actor node/GPU counts for SPMD conversion and Megatron parallel config
• Switch the 64-GPU H200 recipe to TP8 CP1
• Use SGLang router only: R3 adds --use-rollout-routing-replay without enabling Miles router
• Use the DAPO thinking_mode chat-template kwarg
• Set SGLANG_HEALTH_CHECK_TIMEOUT=120 to avoid false rollout health failures during long detokenizer gaps

Validation

• pre-commit run --all-files
• Covered by the DeepSeek V4 16-node disaggregate debug run: 8 training nodes + 8 rollout nodes, R3 enabled, Miles router disabled, reached step 1 with no health failures or engine kills

Related PRs

• Megatron expert-bias update fix: Skip missing expert bias updates Megatron-LM#55
• SGLang DSV4 unloaded warning: Shorten DSV4 unload warning sgl-project/sglang#27603
• SGLang DeepGEMM cache isolation: Isolate DeepGEMM cache per process sgl-project/sglang#27604
• Miles DeepGEMM rollout envs: Set per-process DeepGEMM cache env #1309

[gemini-code-assist]

Code Review

This pull request introduces support for non-colocated actor and rollout configurations in the DeepSeek-V4 training script, adding new arguments (colocate, actor_num_nodes, actor_num_gpus_per_node, and rollout_num_gpus) along with validation logic in __post_init__. It also updates the parallel configuration logic, environment variables, and chat template arguments, and introduces a conditional enable_miles_router flag. The feedback recommends replacing bare assert statements with explicit ValueError exceptions to prevent uninformative errors and avoid issues when Python is run with optimization flags.

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[gemini-code-assist]

Using bare assert statements for input validation in __post_init__ can lead to uninformative AssertionError exceptions and may be optimized away if Python is run with the -O flag. It is better to raise a ValueError with a descriptive error message to improve usability and robustness.

        if self.actor_num_nodes is None:
            if self.colocate:
                self.actor_num_nodes = self.num_nodes
            else:
                if self.num_nodes % 2 != 0:
                    raise ValueError(
                        f"num_nodes ({self.num_nodes}) must be even for non-colocated training "
                        "when actor_num_nodes is not specified."
                    )
                self.actor_num_nodes = self.num_nodes // 2
        if self.actor_num_nodes > self.num_nodes:
            raise ValueError(f"actor_num_nodes ({self.actor_num_nodes}) cannot exceed num_nodes ({self.num_nodes}).")
        if self.actor_num_gpus_per_node > self.num_gpus_per_node:
            raise ValueError(
                f"actor_num_gpus_per_node ({self.actor_num_gpus_per_node}) cannot exceed "
                f"num_gpus_per_node ({self.num_gpus_per_node})."
            )
        if self.rollout_num_gpus is None:
            if self.colocate:
                self.rollout_num_gpus = self.actor_num_nodes * self.actor_num_gpus_per_node
            else:
                self.rollout_num_gpus = (self.num_nodes - self.actor_num_nodes) * self.num_gpus_per_node
        if not self.colocate and self.rollout_num_gpus <= 0:
            raise ValueError("rollout_num_gpus must be greater than 0 when colocate is False.")

[gemini-code-assist]

Using a bare assert statement here can raise an uninformative AssertionError if enable_miles_router is enabled without enable_r3. Raising a ValueError with a clear, actionable error message is much more user-friendly.

Suggested change

	assert args.enable_r3
	if not args.enable_r3:
	raise ValueError("enable_miles_router requires enable_r3 to be True.")