Source code for modelzoo.common.pytorch.model_utils.GPTLMHeadModelLoss

# Copyright 2022 Cerebras Systems.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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# See the License for the specific language governing permissions and
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# TODO: Move to a separate folder when more head models are added like MLM and NSP on bert, etc.

import torch
import torch.nn as nn


[docs]class GPTLMHeadModelLoss(nn.Module):
[docs] def __init__( self, vocab_size, loss_scaling, loss_weight, ): super(GPTLMHeadModelLoss, self).__init__() self.vocab_size = vocab_size self.loss_weight = loss_weight self.loss_scaling = loss_scaling assert ( self.loss_scaling == "num_tokens" or self.loss_scaling == "batch_size" ), f"Loss scaling can't be set to {self.loss_scaling}. \ Should be either 'num_tokens' or 'batch_size'" if self.loss_scaling == "num_tokens": assert ( self.loss_weight == 1.0 ), f"Loss scaling with 'num_tokens' requires loss_weight == 1.0"
def forward( self, lm_logits, labels, attention_mask, reduce_batch=True, ): loss_fct = nn.CrossEntropyLoss(reduction='none') lm_loss = loss_fct( lm_logits.view(-1, self.vocab_size), labels.view(-1).long(), ) if reduce_batch: lm_loss = lm_loss * attention_mask.to(dtype=lm_logits.dtype).view( -1 ) if self.loss_scaling == "num_tokens": lm_loss = torch.sum(lm_loss) / torch.sum( attention_mask.to(dtype=lm_logits.dtype) ) else: lm_loss = ( torch.sum(lm_loss) / labels.shape[0] ) * self.loss_weight loss = lm_loss.to(lm_logits.dtype) else: assert ( self.label_smoothing == 0.0 ), "Label smoothing not supported when reduce_batch=False" loss = lm_loss.view(attention_mask.shape) * attention_mask.to( dtype=lm_logits.dtype ) loss = torch.sum(loss, dim=-1) loss = loss.to(lm_logits.dtype) return loss