299ebb62b2
Signed-off-by: Chanh Nguyen <cnguyen@linkedin.com> Co-authored-by: Chanh Nguyen <cnguyen@linkedin.com>
64 lines
2.7 KiB
Python
64 lines
2.7 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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"""Utility methods for model layers."""
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from typing import Tuple
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import torch
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def get_token_bin_counts_and_mask(
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tokens: torch.Tensor,
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vocab_size: int,
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num_seqs: int,
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) -> Tuple[torch.Tensor, torch.Tensor]:
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# Compute the bin counts for the tokens.
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# vocab_size + 1 for padding.
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bin_counts = torch.zeros((num_seqs, vocab_size + 1),
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dtype=torch.long,
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device=tokens.device)
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bin_counts.scatter_add_(1, tokens, torch.ones_like(tokens))
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bin_counts = bin_counts[:, :vocab_size]
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mask = bin_counts > 0
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return bin_counts, mask
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def apply_penalties(logits: torch.Tensor, prompt_tokens_tensor: torch.Tensor,
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output_tokens_tensor: torch.Tensor,
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presence_penalties: torch.Tensor,
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frequency_penalties: torch.Tensor,
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repetition_penalties: torch.Tensor) -> torch.Tensor:
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"""
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Applies penalties in place to the logits tensor
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logits : The input logits tensor of shape [num_seqs, vocab_size]
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prompt_tokens_tensor: A tensor containing the prompt tokens. The prompts
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are padded to the maximum prompt length within the batch using
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`vocab_size` as the padding value. The value `vocab_size` is used
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for padding because it does not correspond to any valid token ID
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in the vocabulary.
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output_tokens_tensor: The output tokens tensor.
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presence_penalties: The presence penalties of shape (num_seqs, )
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frequency_penalties: The frequency penalties of shape (num_seqs, )
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repetition_penalties: The repetition penalties of shape (num_seqs, )
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"""
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num_seqs, vocab_size = logits.shape
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_, prompt_mask = get_token_bin_counts_and_mask(prompt_tokens_tensor,
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vocab_size, num_seqs)
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output_bin_counts, output_mask = get_token_bin_counts_and_mask(
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output_tokens_tensor, vocab_size, num_seqs)
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repetition_penalties = repetition_penalties.unsqueeze(dim=1).repeat(
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1, vocab_size)
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# If token appears in prompt or output, apply, otherwise use 1.0 for no-op.
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penalties = torch.where(prompt_mask | output_mask, repetition_penalties,
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1.0)
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# If logits are positive, divide by penalty, otherwise multiply by penalty.
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scaling = torch.where(logits > 0, 1.0 / penalties, penalties)
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logits *= scaling
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# We follow the definition in OpenAI API.
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# Refer to https://platform.openai.com/docs/api-reference/parameter-details
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logits -= frequency_penalties.unsqueeze(dim=1) * output_bin_counts
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logits -= presence_penalties.unsqueeze(dim=1) * output_mask
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return logits
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