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35 lines
1.2 KiB
35 lines
1.2 KiB
8 months ago
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"""
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Critic model
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"""
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from typing import Optional
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import torch
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import torch.nn as nn
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from coati.models import BaseModel
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from transformers import PretrainedConfig
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class Critic(BaseModel):
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"""
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Critic model class.
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Args:
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pretrained (str): path to pretrained model.
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config (PretrainedConfig): PretrainedConfig used to initiate the base model.
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"""
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def __init__(self, pretrained: str = None, config: Optional[PretrainedConfig] = None, **kwargs) -> None:
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super().__init__(pretrained=pretrained, config=config, **kwargs)
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# et last hidden state size with dummy input
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self.value_head = nn.Linear(self.last_hidden_state_size, 1)
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def forward(self, input_ids: torch.LongTensor, attention_mask: Optional[torch.Tensor] = None) -> torch.Tensor:
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outputs = self.model(input_ids, attention_mask=attention_mask)
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last_hidden_states = outputs["last_hidden_state"]
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sequence_hidden_states = last_hidden_states[torch.arange(last_hidden_states.size(0)), :].type(
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self.value_head.weight.dtype
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)
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values = self.value_head(sequence_hidden_states).squeeze(-1) # ensure shape is (B, sequence length)
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return values
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