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Fix image token mask in Gemma3 #38295

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Merged
merged 2 commits into from
May 27, 2025
Merged

Fix image token mask in Gemma3 #38295

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64b0290
fix mask
Cyrilvallez May 22, 2025
14ddff8
Merge branch 'main' into gemm3-mask
Cyrilvallez May 27, 2025
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17 changes: 12 additions & 5 deletions src/transformers/models/gemma3/modeling_gemma3.py
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Original file line number Diff line number Diff line change
Expand Up @@ -782,7 +782,7 @@ def forward(self, vision_outputs: torch.Tensor):
return projected_vision_outputs.type_as(vision_outputs)


def token_type_ids_mask_function(token_type_ids: Optional[torch.Tensor]) -> Optional[Callable]:
def token_type_ids_mask_function(token_type_ids: Optional[torch.Tensor], tokens_per_image: int) -> Optional[Callable]:
"""
This function adds the correct offsets to the `q_idx` and `kv_idx` as the torch API can only accept lengths,
not start and end indices.
Expand All @@ -792,8 +792,13 @@ def token_type_ids_mask_function(token_type_ids: Optional[torch.Tensor]) -> Opti
return None

def inner_mask(batch_idx: int, head_idx: int, q_idx: int, kv_idx: int) -> bool:
# If it's 1, we need to unmask it
return token_type_ids[batch_idx, kv_idx] == 1
# If the difference is less than image size, both are part of the same image block
same_image_block = torch.abs(kv_idx - q_idx) <= tokens_per_image
# If it's 1 for both query and key/value, we are in an image block
is_image_block = (token_type_ids[batch_idx, q_idx] == 1) & (token_type_ids[batch_idx, kv_idx] == 1)

# This is bidirectional attention whenever we are dealing with image tokens
return is_image_block & same_image_block

return inner_mask

Expand Down Expand Up @@ -945,7 +950,7 @@ def forward(
if token_type_ids is not None and inputs_embeds.shape[1] != 1:
# We need to pass an additional mask function to account for token type ids, and it needs to be an `or`
mask_kwargs["or_mask_function"] = token_type_ids_mask_function(
token_type_ids.to(cache_position.device)
token_type_ids.to(cache_position.device), self.config.mm_tokens_per_image
)

# Create the masks
Expand Down Expand Up @@ -1211,7 +1216,9 @@ def create_masks_for_generate(
# Add the token type ids mask for generate as well
if token_type_ids is not None and input_embeds.shape[1] != 1:
# We need to pass an additional mask function to account for token type ids, and it needs to be an `or`
mask_kwargs["or_mask_function"] = token_type_ids_mask_function(token_type_ids.to(cache_position.device))
mask_kwargs["or_mask_function"] = token_type_ids_mask_function(
token_type_ids.to(cache_position.device), config.mm_tokens_per_image
)

return create_masks_for_generate(**mask_kwargs)

Expand Down
17 changes: 12 additions & 5 deletions src/transformers/models/gemma3/modular_gemma3.py
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -722,7 +722,7 @@ def forward(self, vision_outputs: torch.Tensor):
return projected_vision_outputs.type_as(vision_outputs)


def token_type_ids_mask_function(token_type_ids: Optional[torch.Tensor]) -> Optional[Callable]:
def token_type_ids_mask_function(token_type_ids: Optional[torch.Tensor], tokens_per_image: int) -> Optional[Callable]:
"""
This function adds the correct offsets to the `q_idx` and `kv_idx` as the torch API can only accept lengths,
not start and end indices.
Expand All @@ -732,8 +732,13 @@ def token_type_ids_mask_function(token_type_ids: Optional[torch.Tensor]) -> Opti
return None

def inner_mask(batch_idx: int, head_idx: int, q_idx: int, kv_idx: int) -> bool:
# If it's 1, we need to unmask it
return token_type_ids[batch_idx, kv_idx] == 1
# If the difference is less than image size, both are part of the same image block
same_image_block = torch.abs(kv_idx - q_idx) <= tokens_per_image
# If it's 1 for both query and key/value, we are in an image block
is_image_block = (token_type_ids[batch_idx, q_idx] == 1) & (token_type_ids[batch_idx, kv_idx] == 1)

# This is bidirectional attention whenever we are dealing with image tokens
return is_image_block & same_image_block

return inner_mask

Expand Down Expand Up @@ -836,7 +841,7 @@ def forward(
if token_type_ids is not None and inputs_embeds.shape[1] != 1:
# We need to pass an additional mask function to account for token type ids, and it needs to be an `or`
mask_kwargs["or_mask_function"] = token_type_ids_mask_function(
token_type_ids.to(cache_position.device)
token_type_ids.to(cache_position.device), self.config.mm_tokens_per_image
)

# Create the masks
Expand Down Expand Up @@ -1055,7 +1060,9 @@ def create_masks_for_generate(
# Add the token type ids mask for generate as well
if token_type_ids is not None and input_embeds.shape[1] != 1:
# We need to pass an additional mask function to account for token type ids, and it needs to be an `or`
mask_kwargs["or_mask_function"] = token_type_ids_mask_function(token_type_ids.to(cache_position.device))
mask_kwargs["or_mask_function"] = token_type_ids_mask_function(
token_type_ids.to(cache_position.device), config.mm_tokens_per_image
)

return create_masks_for_generate(**mask_kwargs)

Expand Down