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Llama4: remove redundant transpose of router_logits #37468

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Merged
merged 2 commits into from
Apr 15, 2025
Merged

Llama4: remove redundant transpose of router_logits #37468

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Llama4: remove redundant transpose of router_logits
pbelevich Apr 12, 2025
b935ef0
Fix formatting
pbelevich Apr 12, 2025
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8 changes: 3 additions & 5 deletions src/transformers/models/llama4/modeling_llama4.py
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Original file line number Diff line number Diff line change
Expand Up @@ -159,14 +159,12 @@ def __init__(self, config):
def forward(self, hidden_states):
batch, seq_len, hidden_dim = hidden_states.shape
hidden_states = hidden_states.view(-1, self.hidden_dim)
router_logits = self.router(hidden_states).transpose(0, 1)
router_logits = self.router(hidden_states)
tokens_per_expert = batch * seq_len

router_top_value, router_indices = torch.topk(router_logits.transpose(0, 1), self.top_k, dim=1)
router_top_value, router_indices = torch.topk(router_logits, self.top_k, dim=1)
router_scores = (
torch.full_like(router_logits.transpose(0, 1), float("-inf"))
.scatter_(1, router_indices, router_top_value)
.transpose(0, 1)
torch.full_like(router_logits, float("-inf")).scatter_(1, router_indices, router_top_value).transpose(0, 1)
)
# We do this to make sure we have -inf for non topK tokens before going through the !
# Here we are just creating a tensor to index each and every single one of the hidden states. Let s maybe register a buffer for this!
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