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[cache] Only use scalars in get_mask_sizes #40907

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Merged
merged 3 commits into from
Sep 16, 2025
Merged

[cache] Only use scalars in get_mask_sizes #40907

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8d7557d
remove tensor ops
Cyrilvallez Sep 16, 2025
e5c9c05
style
Cyrilvallez Sep 16, 2025
6a513b6
style
Cyrilvallez Sep 16, 2025
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15 changes: 7 additions & 8 deletions src/transformers/cache_utils.py
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Original file line number Diff line number Diff line change
Expand Up @@ -122,8 +122,7 @@ def get_mask_sizes(self, cache_position: torch.Tensor) -> tuple[int, int]:
"""Return the length and offset of the cache, used to generate the mask"""
kv_offset = 0
query_length = cache_position.shape[0]
past_seen_tokens = self.get_seq_length()
kv_length = query_length + past_seen_tokens
kv_length = self.get_seq_length() + query_length
return kv_length, kv_offset

def get_seq_length(self) -> int:
Expand Down Expand Up @@ -212,14 +211,13 @@ def update(
def get_mask_sizes(self, cache_position: torch.Tensor) -> tuple[int, int]:
"""Return the length and offset of the cache, used to generate the attention mask"""
query_length = cache_position.shape[0]
first_cache_position = cache_position[0]
is_full = self.cumulative_length >= self.sliding_window

kv_offset = torch.clamp(first_cache_position - self.sliding_window + 1, min=0)

if self.get_seq_length() >= self.sliding_window:
kv_offset = max(self.cumulative_length - self.sliding_window + 1, 0)
if is_full:
kv_length = self.sliding_window - 1 + query_length
else:
kv_length = self.get_seq_length() + query_length
kv_length = self.cumulative_length + query_length

return kv_length, kv_offset

Expand Down Expand Up @@ -461,9 +459,10 @@ def get_mask_sizes(self, cache_position: torch.Tensor) -> tuple[int, int]:
# Not yet full, but becoming full on this update
elif self.cumulative_length + query_length > sliding_window:
kv_length = self.cumulative_length + query_length
# Here the Cache is still smaller than the local size, but we return the local size as it's static
else:
# Here the Cache is still smaller than the local size, but we return the local size as it's static
kv_length = sliding_window

return kv_length, kv_offset

def get_seq_length(self) -> int:
Expand Down