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(fix): fix get_pad_mask for eos_token_id and pad_token_id. #304

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Merged
PanAndy merged 1 commit into from
Dec 22, 2025
Merged

(fix): fix get_pad_mask for eos_token_id and pad_token_id. #304

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17 changes: 15 additions & 2 deletions roll/utils/functionals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -307,13 +307,26 @@ def get_eos_mask(response_id: torch.Tensor, eos_token: int = 2, dtype=torch.int6
return eos_mask


def get_pad_mask(response_id: torch.Tensor, pad_token: int = 0, dtype=torch.int64):
def get_pad_mask(response_id: torch.Tensor, pad_token: int = 0, eos_token: int = 1, dtype=torch.int64):
"""
e.g. pad token=0
response_id: [1, 2, 2, 42, 3, 5, 1, 0, 0]
pad_mask: [1, 1, 1, 1, 1, 1, 1, 0, 0]

If eos_token == pad_token, the first pad token (which is the eos token) should be kept.
e.g. pad_token=0, eos_token=0
response_id: [1, 2, 2, 42, 3, 5, 0, 0, 0]
pad_mask: [1, 1, 1, 1, 1, 1, 1, 0, 0] (first pad token/eos token is kept)
"""
pad_mask = response_id.not_equal(pad_token).to(dtype)

# eos_token == pad_token, 需要保留第一个pad token否则会误将eos token mask掉
if eos_token == pad_token:
pad_positions = response_id.eq(pad_token).to(dtype)
cumsum_pad = torch.cumsum(pad_positions, dim=-1)
first_pad_token = (cumsum_pad == 1).to(dtype)
pad_mask = pad_mask | first_pad_token

assert (
not (pad_mask[:, 0] == 0).logical_and(pad_mask.sum(-1) != 0).any()
), f"response_id is not valid: {response_id}, pad_token is {pad_token}"
Expand Down Expand Up @@ -812,7 +825,7 @@ def postprocess_generate(
attention_mask = (
attention_mask.unsqueeze(1).repeat(1, num_return_sequences, 1).view(output_batch_size, prompt_length)
)
response_mask = get_pad_mask(response_id=response, pad_token=pad_token_id, dtype=attention_mask.dtype)
response_mask = get_pad_mask(response_id=response, pad_token=pad_token_id, eos_token=eos_token_id, dtype=attention_mask.dtype)
attention_mask = torch.cat((attention_mask, response_mask), dim=-1)

position_ids = prompts.batch["position_ids"]
Expand Down