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[Misc][Quantization] Clarify the intent of GGUF FusedMoE weight materialization #30310

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Merged
Isotr0py merged 1 commit into from
Dec 13, 2025
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[Misc][Quantization] Clarify the intent of GGUF FusedMoE weight materialization #30310

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8 changes: 6 additions & 2 deletions vllm/model_executor/layers/fused_moe/layer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1200,10 +1200,14 @@ def weight_loader(
if full_load:
shard_dim += 1

# Materialize GGUF UninitializedParameter
# Materialize GGUF UninitializedParameter accounting merged weights
if is_gguf_weight and isinstance(param, UninitializedParameter):
# To materialize a tensor, we must have full shape including
# number of experts, making this portion to require `full_load`.
assert full_load
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@Isotr0py Isotr0py Dec 9, 2025

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Perhaps add a message to clarify what's happening when assertion is false?

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@a4lg a4lg Dec 9, 2025

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Hmm, rather, it would be better to improve the comment (i.e. what is truly necessary). I'll consider changing around this line.

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@a4lg a4lg Dec 13, 2025

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I changed the comment to note why full_load is required.

Before:

# GGUF currently requires full load (3D tensors).

After:

# To materialize a tensor, we must have full shape including
# number of experts, making this portion to require `full_load`.

final_shape = list(loaded_weight.shape)
if shard_id in ["w1", "w3"]:
# w1 and w3 are merged per expert.
if shard_id in {"w1", "w3"}:
final_shape[1] *= 2
final_shape[shard_dim] = final_shape[shard_dim] // self.tp_size
param.materialize(final_shape, dtype=loaded_weight.dtype)
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