Source code for modelzoo.common.pytorch.layers.TransformerEncoder

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"""
Adapted from https://github.com/pytorch/pytorch/blob/master/torch/nn/modules/transformer.py
"""

from typing import Optional

import torch.nn as nn
from torch import Tensor

from modelzoo.common.pytorch.layers.utils import _get_clones


[docs]class TransformerEncoder(nn.Module): r"""TransformerEncoder is a stack of N encoder layers Args: encoder_layer: an instance of the TransformerEncoderLayer() class (required). num_layers: the number of sub-encoder-layers in the encoder (required). norm: the layer normalization component (optional). enable_nested_tensor: if True, input will automatically convert to nested tensor (and convert back on output). This will improve the overall performance of TransformerEncoder when padding rate is high. Default: ``False`` (disabled). Examples:: >>> encoder_layer = nn.TransformerEncoderLayer(d_model=512, nhead=8) >>> transformer_encoder = nn.TransformerEncoder(encoder_layer, num_layers=6) >>> src = torch.rand(10, 32, 512) >>> out = transformer_encoder(src) """
[docs] def __init__( self, encoder_layer, num_layers, norm=None, enable_nested_tensor=False ): super(TransformerEncoder, self).__init__() assert not enable_nested_tensor, "Nested tensors are not supported." self.layers = _get_clones(encoder_layer, num_layers) self.num_layers = num_layers self.norm = norm # Re-initialize all layers to get new set of weights for each layer self.__reset_parameters()
def reset_parameters(self): self.__reset_parameters() def __reset_parameters(self): for layer in self.layers: layer.reset_parameters() if self.norm: if hasattr(self.norm, 'bias') and hasattr(self.norm.bias, "data"): self.norm.bias.data.zero_() if hasattr(self.norm, 'weight') and hasattr( self.norm.weight, "data" ): self.norm.weight.data.fill_(1.0)
[docs] def forward( self, src: Tensor, mask: Optional[Tensor] = None, src_key_padding_mask: Optional[Tensor] = None, self_attn_position_bias: Optional[Tensor] = None, **extra_args, ) -> Tensor: r"""Pass the input through the encoder layers in turn. Args: src: the sequence to the encoder (required). mask: the mask for the src sequence (optional). src_key_padding_mask: the mask for the src keys per batch (optional). self_attn_position_bias: the tensor containing position bias to apply in self-attention, can be obtained from relative or alibi position embeddings. Shape: see the docs in Transformer class. """ output = src for mod in self.layers: output = mod( output, src_mask=mask, src_key_padding_mask=src_key_padding_mask, self_attn_position_bias=self_attn_position_bias, **extra_args, ) if self.norm is not None: output = self.norm(output) return output