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Support newer Megatron-Core / Megatron-Bridge (nemo:26.10) in Minitron pruning and Puzzletron - #2922
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… Puzzletron Newer MCore (e.g. nemo:26.10) refreshes the Mamba -exp(A_log) decode cache on eval(), gives each hybrid layer its own config copy and keeps per-layer lists index-aligned with HybridStack.layers; newer Megatron-Bridge derives gtp_weight_remat_size in __post_init__. Resize the cache to the active heads, slice/restore the per-layer lists when dropping layers, write the pruned architecture to the per-layer configs, and pass only init fields to GenericHeterogeneousProvider. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Keval Morabia <28916987+kevalmorabia97@users.noreply.github.com>
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The title clearly and concisely identifies the main compatibility changes for newer Megatron-Core and Megatron-Bridge versions in Minitron pruning and Puzzletron. |
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Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 8 functions across 3 files. (1 skipped: 1 … |
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PASS. The pull request changes only three Python files and the changelog. Added code contains no new torch.load(..., weights_only=False), numpy.load(..., allow_pickle=True), trust_remote_code=True, ev… |
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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Signed-off-by: Keval Morabia <28916987+kevalmorabia97@users.noreply.github.com>
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Review comments at @modelopt/torch/prune/plugins/mcore_minitron.py:
- Around line 467-470: The _prune candidate-state restoration must snapshot
independent copies of each per-layer hybrid config, not just the container
referenced by saved_stack_state. Capture fields mutated during pruning,
including hidden_size, num_layers, and derived attention/FFN sizes, before
candidate evaluation and restore them for subsequent candidates and final
export.
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📒 Files selected for processing: 4
CHANGELOG.rstmodelopt/torch/nas/plugins/megatron.pymodelopt/torch/prune/plugins/mcore_minitron.pymodelopt/torch/puzzletron/plugins/mbridge/base.py
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Additional details and impacted files@@ Coverage Diff @@
## main #2922 +/- ##
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+ Coverage 70.16% 78.91% +8.75%
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Files 659 659
Lines 74081 74103 +22
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+ Hits 51979 58481 +6502
+ Misses 22102 15622 -6480
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What does this PR do?
Type of change: Compatibility update (newer Megatron-Core / Megatron-Bridge)
Makes Minitron pruning of Mamba hybrid models and Puzzletron distillation work with newer Megatron-Core / Megatron-Bridge. The NeMo 26.10 container ships these changes. Without this PR, 4 Megatron GPU or example tests fail there, while they pass on nemo:26.08. Each fix is a no-op on the older versions, and none is a shim to drop once nemo:26.10 is the minimum: the newer MCore needs all of them, and the
hasattrchecks also tell GPT models (TransformerBlock) apart from hybrid ones._DynamicMambaMixer):MambaMixerkeeps a per-head-exp(A_log)cache that newer MCore refreshes on everyeval(). Once pruning shrinks the active heads, the refresh fails withThe size of tensor a (8) must match the size of tensor b (6). The cache is now resized to the active heads intrain()and afterexport().drop_mcore_language_model_layers): newerHybridStackkeepslayer_config_listand its execution lists index-aligned withlayers, and its forward zips them withstrict=True. Dropping layers now slices them too, and_temporarily_prunedrestores them after scoring a candidate. Grouped shortcut-MoE blocks are rejected before anything is mutated.MCoreMinitronSearcher._prune): each hybrid layer now holds its own copy of the config. The pruned architecture is now written to those copies as well asmodel.config. Megatron-Bridge's Mambain_projexport reads the layer's config, so before this fix exporting a pruned Nemotron-H hit a device-side index-out-of-bounds.HeterogeneousBridgeMixin.provider_bridge): newer Megatron-Bridge derivesgtp_weight_remat_sizein__post_init__(init=False), so only fields the constructor accepts are passed.This unblocks testing ModelOpt's Megatron CI against a newer Megatron-Bridge before nemo:26.10 is out (planned on top of #2889).
Testing
Run with a newer Megatron-Bridge (and its Megatron-LM submodule) on nemo:26.08:
src/megatron/bridgeand3rdparty/Megatron-LM/megatronreplaced from Megatron-Bridge main + NVIDIA-NeMo/Megatron-Bridge#6565:tests/examples/megatron_bridge: 98 passed, 2 failed (test_distill_puzzletron_anymodel,test_prune_minitron[nemotron_h]).tests/gpu_megatron: 448 passed, 4 failed.test_mcore_hybrid_pruning_nas_paramswas the real failure; the other 3 were OOMs from GPU contention and pass when rerun alone.tests/gpu_megatron/torch/{prune,nas}: 62 passed.test_prune_minitron[nemotron_h]andtest_distill_puzzletron_anymodel: pass.test_mamba_search_space,test_mcore_hybrid_pruning_nas_params,test_prune_minitron[nemotron_h]. The existing tests cover these paths once CI runs a newer MCore, so no new tests.Stock nemo:26.08, with this PR:
tests/gpu_megatron/torch/{prune,nas}: 62 passed.tests/examples/megatron_bridge/test_prune_minitron.pyandtest_distill.py: 19 passed.Not run: the nemo:26.10 container itself (its rc has the same Megatron-Core changes), and the full
tests/gpu_megatronwith this PR.Before your PR is "Ready for review"
CONTRIBUTING.md: N/AAdditional Information
Related: #2889 (Megatron-Bridge fake-quant export, whose CI bump depends on this), NVIDIA-NeMo/Megatron-Bridge#6565.
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