diff --git a/egs/librispeech/ASR/incremental_transf/.conformer.py.swp b/egs/librispeech/ASR/incremental_transf/.conformer.py.swp deleted file mode 100644 index 84d33d1fe..000000000 Binary files a/egs/librispeech/ASR/incremental_transf/.conformer.py.swp and /dev/null differ diff --git a/egs/librispeech/ASR/pruned_transducer_stateless_gtrans/conformer_old.py b/egs/librispeech/ASR/pruned_transducer_stateless_gtrans/conformer_old.py new file mode 100644 index 000000000..f94ffef59 --- /dev/null +++ b/egs/librispeech/ASR/pruned_transducer_stateless_gtrans/conformer_old.py @@ -0,0 +1,1593 @@ +#!/usr/bin/env python3 +# Copyright (c) 2021 University of Chinese Academy of Sciences (author: Han Zhu) +# +# See ../../../../LICENSE for clarification regarding multiple authors +# +# 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 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +import copy +import math +import warnings +from typing import List, Optional, Tuple + +import torch +from encoder_interface import EncoderInterface +from scaling import ( + ActivationBalancer, + BasicNorm, + DoubleSwish, + ScaledConv1d, + ScaledConv2d, + ScaledLinear, +) +from torch import Tensor, nn + +from icefall.utils import is_jit_tracing, make_pad_mask, subsequent_chunk_mask + + +class Conformer(EncoderInterface): + """ + Args: + num_features (int): Number of input features + subsampling_factor (int): subsampling factor of encoder (the convolution layers before transformers) + d_model (int): attention dimension, also the output dimension + nhead (int): number of head + dim_feedforward (int): feedforward dimention + num_encoder_layers (int): number of encoder layers + dropout (float): dropout rate + layer_dropout (float): layer-dropout rate. + cnn_module_kernel (int): Kernel size of convolution module + vgg_frontend (bool): whether to use vgg frontend. + dynamic_chunk_training (bool): whether to use dynamic chunk training, if + you want to train a streaming model, this is expected to be True. + When setting True, it will use a masking strategy to make the attention + see only limited left and right context. + short_chunk_threshold (float): a threshold to determinize the chunk size + to be used in masking training, if the randomly generated chunk size + is greater than ``max_len * short_chunk_threshold`` (max_len is the + max sequence length of current batch) then it will use + full context in training (i.e. with chunk size equals to max_len). + This will be used only when dynamic_chunk_training is True. + short_chunk_size (int): see docs above, if the randomly generated chunk + size equals to or less than ``max_len * short_chunk_threshold``, the + chunk size will be sampled uniformly from 1 to short_chunk_size. + This also will be used only when dynamic_chunk_training is True. + num_left_chunks (int): the left context (in chunks) attention can see, the + chunk size is decided by short_chunk_threshold and short_chunk_size. + A minus value means seeing full left context. + This also will be used only when dynamic_chunk_training is True. + causal (bool): Whether to use causal convolution in conformer encoder + layer. This MUST be True when using dynamic_chunk_training. + """ + + def __init__( + self, + num_features: int, + subsampling_factor: int = 4, + d_model: int = 256, + nhead: int = 4, + dim_feedforward: int = 2048, + num_encoder_layers: int = 12, + dropout: float = 0.1, + layer_dropout: float = 0.075, + cnn_module_kernel: int = 31, + dynamic_chunk_training: bool = False, + short_chunk_threshold: float = 0.75, + short_chunk_size: int = 25, + num_left_chunks: int = -1, + causal: bool = False, + ) -> None: + super(Conformer, self).__init__() + + self.num_features = num_features + self.subsampling_factor = subsampling_factor + if subsampling_factor != 4: + raise NotImplementedError("Support only 'subsampling_factor=4'.") + + # self.encoder_embed converts the input of shape (N, T, num_features) + # to the shape (N, T//subsampling_factor, d_model). + # That is, it does two things simultaneously: + # (1) subsampling: T -> T//subsampling_factor + # (2) embedding: num_features -> d_model + self.encoder_embed = Conv2dSubsampling(num_features, d_model) + + self.encoder_layers = num_encoder_layers + self.d_model = d_model + self.cnn_module_kernel = cnn_module_kernel + self.causal = causal + self.dynamic_chunk_training = dynamic_chunk_training + self.short_chunk_threshold = short_chunk_threshold + self.short_chunk_size = short_chunk_size + self.num_left_chunks = num_left_chunks + + self.encoder_pos = RelPositionalEncoding(d_model, dropout) + + encoder_layer = ConformerEncoderLayer( + d_model, + nhead, + dim_feedforward, + dropout, + layer_dropout, + cnn_module_kernel, + causal, + ) + self.encoder = ConformerEncoder(encoder_layer, num_encoder_layers) + self._init_state: List[torch.Tensor] = [torch.empty(0)] + + def forward( + self, x: torch.Tensor, x_lens: torch.Tensor, warmup: float = 1.0 + ) -> Tuple[torch.Tensor, torch.Tensor]: + """ + Args: + x: + The input tensor. Its shape is (batch_size, seq_len, feature_dim). + x_lens: + A tensor of shape (batch_size,) containing the number of frames in + `x` before padding. + warmup: + A floating point value that gradually increases from 0 throughout + training; when it is >= 1.0 we are "fully warmed up". It is used + to turn modules on sequentially. + Returns: + Return a tuple containing 2 tensors: + - embeddings: its shape is (batch_size, output_seq_len, d_model) + - lengths, a tensor of shape (batch_size,) containing the number + of frames in `embeddings` before padding. + """ + x = self.encoder_embed(x) + x, pos_emb = self.encoder_pos(x) + x = x.permute(1, 0, 2) # (N, T, C) -> (T, N, C) + + # Caution: We assume the subsampling factor is 4! + + # lengths = ((x_lens - 1) // 2 - 1) // 2 # issue an warning + # + # Note: rounding_mode in torch.div() is available only in torch >= 1.8.0 + lengths = (((x_lens - 1) >> 1) - 1) >> 1 + + if not is_jit_tracing(): + assert x.size(0) == lengths.max().item() + + src_key_padding_mask = make_pad_mask(lengths) + + if self.dynamic_chunk_training: + assert ( + self.causal + ), "Causal convolution is required for streaming conformer." + max_len = x.size(0) + chunk_size = torch.randint(1, max_len, (1,)).item() + if chunk_size > (max_len * self.short_chunk_threshold): + chunk_size = max_len + else: + chunk_size = chunk_size % self.short_chunk_size + 1 + + mask = ~subsequent_chunk_mask( + size=x.size(0), + chunk_size=chunk_size, + num_left_chunks=self.num_left_chunks, + device=x.device, + ) + x = self.encoder( + x, + pos_emb, + mask=mask, + src_key_padding_mask=src_key_padding_mask, + warmup=warmup, + ) # (T, N, C) + else: + x = self.encoder( + x, + pos_emb, + mask=None, + src_key_padding_mask=src_key_padding_mask, + warmup=warmup, + ) # (T, N, C) + + x = x.permute(1, 0, 2) # (T, N, C) ->(N, T, C) + return x, lengths + + @torch.jit.export + def get_init_state( + self, left_context: int, device: torch.device + ) -> List[torch.Tensor]: + """Return the initial cache state of the model. + + Args: + left_context: The left context size (in frames after subsampling). + + Returns: + Return the initial state of the model, it is a list containing two + tensors, the first one is the cache for attentions which has a shape + of (num_encoder_layers, left_context, encoder_dim), the second one + is the cache of conv_modules which has a shape of + (num_encoder_layers, cnn_module_kernel - 1, encoder_dim). + + NOTE: the returned tensors are on the given device. + """ + if len(self._init_state) == 2 and self._init_state[0].size(1) == left_context: + # Note: It is OK to share the init state as it is + # not going to be modified by the model + return self._init_state + + init_states: List[torch.Tensor] = [ + torch.zeros( + ( + self.encoder_layers, + left_context, + self.d_model, + ), + device=device, + ), + torch.zeros( + ( + self.encoder_layers, + self.cnn_module_kernel - 1, + self.d_model, + ), + device=device, + ), + ] + + self._init_state = init_states + + return init_states + + @torch.jit.export + def streaming_forward( + self, + x: torch.Tensor, + x_lens: torch.Tensor, + states: Optional[List[Tensor]] = None, + processed_lens: Optional[Tensor] = None, + left_context: int = 64, + right_context: int = 4, + chunk_size: int = 16, + simulate_streaming: bool = False, + warmup: float = 1.0, + ) -> Tuple[torch.Tensor, torch.Tensor, List[torch.Tensor]]: + """ + Args: + x: + The input tensor. Its shape is (batch_size, seq_len, feature_dim). + x_lens: + A tensor of shape (batch_size,) containing the number of frames in + `x` before padding. + states: + The decode states for previous frames which contains the cached data. + It has two elements, the first element is the attn_cache which has + a shape of (encoder_layers, left_context, batch, attention_dim), + the second element is the conv_cache which has a shape of + (encoder_layers, cnn_module_kernel-1, batch, conv_dim). + Note: states will be modified in this function. + processed_lens: + How many frames (after subsampling) have been processed for each sequence. + left_context: + How many previous frames the attention can see in current chunk. + Note: It's not that each individual frame has `left_context` frames + of left context, some have more. + right_context: + How many future frames the attention can see in current chunk. + Note: It's not that each individual frame has `right_context` frames + of right context, some have more. + chunk_size: + The chunk size for decoding, this will be used to simulate streaming + decoding using masking. + simulate_streaming: + If setting True, it will use a masking strategy to simulate streaming + fashion (i.e. every chunk data only see limited left context and + right context). The whole sequence is supposed to be send at a time + When using simulate_streaming. + warmup: + A floating point value that gradually increases from 0 throughout + training; when it is >= 1.0 we are "fully warmed up". It is used + to turn modules on sequentially. + Returns: + Return a tuple containing 2 tensors: + - logits, its shape is (batch_size, output_seq_len, output_dim) + - logit_lens, a tensor of shape (batch_size,) containing the number + of frames in `logits` before padding. + - decode_states, the updated states including the information + of current chunk. + """ + + # x: [N, T, C] + # Caution: We assume the subsampling factor is 4! + + # lengths = ((x_lens - 1) // 2 - 1) // 2 # issue an warning + # + # Note: rounding_mode in torch.div() is available only in torch >= 1.8.0 + lengths = (((x_lens - 1) >> 1) - 1) >> 1 + + if not simulate_streaming: + assert states is not None + assert processed_lens is not None + assert ( + len(states) == 2 + and states[0].shape + == (self.encoder_layers, left_context, x.size(0), self.d_model) + and states[1].shape + == ( + self.encoder_layers, + self.cnn_module_kernel - 1, + x.size(0), + self.d_model, + ) + ), f"""The length of states MUST be equal to 2, and the shape of + first element should be {(self.encoder_layers, left_context, x.size(0), self.d_model)}, + given {states[0].shape}. the shape of second element should be + {(self.encoder_layers, self.cnn_module_kernel - 1, x.size(0), self.d_model)}, + given {states[1].shape}.""" + + lengths -= 2 # we will cut off 1 frame on each side of encoder_embed output + + src_key_padding_mask = make_pad_mask(lengths) + + processed_mask = torch.arange(left_context, device=x.device).expand( + x.size(0), left_context + ) + processed_lens = processed_lens.view(x.size(0), 1) + processed_mask = (processed_lens <= processed_mask).flip(1) + + src_key_padding_mask = torch.cat( + [processed_mask, src_key_padding_mask], dim=1 + ) + + embed = self.encoder_embed(x) + + # cut off 1 frame on each size of embed as they see the padding + # value which causes a training and decoding mismatch. + embed = embed[:, 1:-1, :] + + embed, pos_enc = self.encoder_pos(embed, left_context) + embed = embed.permute(1, 0, 2) # (B, T, F) -> (T, B, F) + + x, states = self.encoder.chunk_forward( + embed, + pos_enc, + src_key_padding_mask=src_key_padding_mask, + warmup=warmup, + states=states, + left_context=left_context, + right_context=right_context, + ) # (T, B, F) + if right_context > 0: + x = x[0:-right_context, ...] + lengths -= right_context + else: + assert states is None + states = [] # just to make torch.script.jit happy + # this branch simulates streaming decoding using mask as we are + # using in training time. + src_key_padding_mask = make_pad_mask(lengths) + x = self.encoder_embed(x) + x, pos_emb = self.encoder_pos(x) + x = x.permute(1, 0, 2) # (N, T, C) -> (T, N, C) + + assert x.size(0) == lengths.max().item() + + num_left_chunks = -1 + if left_context >= 0: + assert left_context % chunk_size == 0 + num_left_chunks = left_context // chunk_size + + mask = ~subsequent_chunk_mask( + size=x.size(0), + chunk_size=chunk_size, + num_left_chunks=num_left_chunks, + device=x.device, + ) + x = self.encoder( + x, + pos_emb, + mask=mask, + src_key_padding_mask=src_key_padding_mask, + warmup=warmup, + ) # (T, N, C) + + x = x.permute(1, 0, 2) # (T, N, C) ->(N, T, C) + + return x, lengths, states + + +class ConformerEncoderLayer(nn.Module): + """ + ConformerEncoderLayer is made up of self-attn, feedforward and convolution networks. + See: "Conformer: Convolution-augmented Transformer for Speech Recognition" + + Args: + d_model: the number of expected features in the input (required). + nhead: the number of heads in the multiheadattention models (required). + dim_feedforward: the dimension of the feedforward network model (default=2048). + dropout: the dropout value (default=0.1). + cnn_module_kernel (int): Kernel size of convolution module. + causal (bool): Whether to use causal convolution in conformer encoder + layer. This MUST be True when using dynamic_chunk_training and streaming decoding. + + Examples:: + >>> encoder_layer = ConformerEncoderLayer(d_model=512, nhead=8) + >>> src = torch.rand(10, 32, 512) + >>> pos_emb = torch.rand(32, 19, 512) + >>> out = encoder_layer(src, pos_emb) + """ + + def __init__( + self, + d_model: int, + nhead: int, + dim_feedforward: int = 2048, + dropout: float = 0.1, + layer_dropout: float = 0.075, + cnn_module_kernel: int = 31, + causal: bool = False, + ) -> None: + super(ConformerEncoderLayer, self).__init__() + + self.layer_dropout = layer_dropout + + self.d_model = d_model + + self.self_attn = RelPositionMultiheadAttention(d_model, nhead, dropout=0.0) + + self.feed_forward = nn.Sequential( + ScaledLinear(d_model, dim_feedforward), + ActivationBalancer(channel_dim=-1), + DoubleSwish(), + nn.Dropout(dropout), + ScaledLinear(dim_feedforward, d_model, initial_scale=0.25), + ) + + self.feed_forward_macaron = nn.Sequential( + ScaledLinear(d_model, dim_feedforward), + ActivationBalancer(channel_dim=-1), + DoubleSwish(), + nn.Dropout(dropout), + ScaledLinear(dim_feedforward, d_model, initial_scale=0.25), + ) + + self.conv_module = ConvolutionModule(d_model, cnn_module_kernel, causal=causal) + + self.norm_final = BasicNorm(d_model) + + # try to ensure the output is close to zero-mean (or at least, zero-median). + self.balancer = ActivationBalancer( + channel_dim=-1, min_positive=0.45, max_positive=0.55, max_abs=6.0 + ) + + self.dropout = nn.Dropout(dropout) + + def forward( + self, + src: Tensor, + pos_emb: Tensor, + src_key_padding_mask: Optional[Tensor] = None, + src_mask: Optional[Tensor] = None, + warmup: float = 1.0, + ) -> Tensor: + """ + Pass the input through the encoder layer. + + Args: + src: the sequence to the encoder layer (required). + pos_emb: Positional embedding tensor (required). + src_key_padding_mask: the mask for the src keys per batch (optional). + src_mask: the mask for the src sequence (optional). + warmup: controls selective bypass of of layers; if < 1.0, we will + bypass layers more frequently. + Shape: + src: (S, N, E). + pos_emb: (N, 2*S-1, E) + src_mask: (S, S). + src_key_padding_mask: (N, S). + S is the source sequence length, N is the batch size, E is the feature number + """ + src_orig = src + + warmup_scale = min(0.1 + warmup, 1.0) + # alpha = 1.0 means fully use this encoder layer, 0.0 would mean + # completely bypass it. + if self.training: + alpha = ( + warmup_scale + if torch.rand(()).item() <= (1.0 - self.layer_dropout) + else 0.1 + ) + else: + alpha = 1.0 + + # macaron style feed forward module + src = src + self.dropout(self.feed_forward_macaron(src)) + + # multi-headed self-attention module + src_att = self.self_attn( + src, + src, + src, + pos_emb=pos_emb, + attn_mask=src_mask, + key_padding_mask=src_key_padding_mask, + )[0] + + src = src + self.dropout(src_att) + + # convolution module + conv, _ = self.conv_module(src, src_key_padding_mask=src_key_padding_mask) + src = src + self.dropout(conv) + + # feed forward module + src = src + self.dropout(self.feed_forward(src)) + + src = self.norm_final(self.balancer(src)) + + if alpha != 1.0: + src = alpha * src + (1 - alpha) * src_orig + + return src + + @torch.jit.export + def chunk_forward( + self, + src: Tensor, + pos_emb: Tensor, + states: List[Tensor], + src_mask: Optional[Tensor] = None, + src_key_padding_mask: Optional[Tensor] = None, + warmup: float = 1.0, + left_context: int = 0, + right_context: int = 0, + ) -> Tuple[Tensor, List[Tensor]]: + """ + Pass the input through the encoder layer. + + Args: + src: the sequence to the encoder layer (required). + pos_emb: Positional embedding tensor (required). + states: + The decode states for previous frames which contains the cached data. + It has two elements, the first element is the attn_cache which has + a shape of (left_context, batch, attention_dim), + the second element is the conv_cache which has a shape of + (cnn_module_kernel-1, batch, conv_dim). + Note: states will be modified in this function. + src_mask: the mask for the src sequence (optional). + src_key_padding_mask: the mask for the src keys per batch (optional). + warmup: controls selective bypass of of layers; if < 1.0, we will + bypass layers more frequently. + left_context: + How many previous frames the attention can see in current chunk. + Note: It's not that each individual frame has `left_context` frames + of left context, some have more. + right_context: + How many future frames the attention can see in current chunk. + Note: It's not that each individual frame has `right_context` frames + of right context, some have more. + + Shape: + src: (S, N, E). + pos_emb: (N, 2*(S+left_context)-1, E). + src_mask: (S, S). + src_key_padding_mask: (N, S). + S is the source sequence length, N is the batch size, E is the feature number + """ + + assert not self.training + assert len(states) == 2 + assert states[0].shape == (left_context, src.size(1), src.size(2)) + + # macaron style feed forward module + src = src + self.dropout(self.feed_forward_macaron(src)) + + # We put the attention cache this level (i.e. before linear transformation) + # to save memory consumption, when decoding in streaming fashion, the + # batch size would be thousands (for 32GB machine), if we cache key & val + # separately, it needs extra several GB memory. + # TODO(WeiKang): Move cache to self_attn level (i.e. cache key & val + # separately) if needed. + key = torch.cat([states[0], src], dim=0) + val = key + if right_context > 0: + states[0] = key[ + -(left_context + right_context) : -right_context, ... # noqa + ] + else: + states[0] = key[-left_context:, ...] + + # multi-headed self-attention module + src_att = self.self_attn( + src, + key, + val, + pos_emb=pos_emb, + attn_mask=src_mask, + key_padding_mask=src_key_padding_mask, + left_context=left_context, + )[0] + + src = src + self.dropout(src_att) + + # convolution module + conv, conv_cache = self.conv_module(src, states[1], right_context) + states[1] = conv_cache + + src = src + self.dropout(conv) + + # feed forward module + src = src + self.dropout(self.feed_forward(src)) + + src = self.norm_final(self.balancer(src)) + + return src, states + + +class ConformerEncoder(nn.Module): + r"""ConformerEncoder is a stack of N encoder layers + + Args: + encoder_layer: an instance of the ConformerEncoderLayer() class (required). + num_layers: the number of sub-encoder-layers in the encoder (required). + + Examples:: + >>> encoder_layer = ConformerEncoderLayer(d_model=512, nhead=8) + >>> conformer_encoder = ConformerEncoder(encoder_layer, num_layers=6) + >>> src = torch.rand(10, 32, 512) + >>> pos_emb = torch.rand(32, 19, 512) + >>> out = conformer_encoder(src, pos_emb) + """ + + def __init__(self, encoder_layer: nn.Module, num_layers: int) -> None: + super().__init__() + self.layers = nn.ModuleList( + [copy.deepcopy(encoder_layer) for i in range(num_layers)] + ) + self.num_layers = num_layers + + def forward( + self, + src: Tensor, + pos_emb: Tensor, + src_key_padding_mask: Optional[Tensor] = None, + mask: Optional[Tensor] = None, + warmup: float = 1.0, + ) -> Tensor: + r"""Pass the input through the encoder layers in turn. + + Args: + src: the sequence to the encoder (required). + pos_emb: Positional embedding tensor (required). + src_key_padding_mask: the mask for the src keys per batch (optional). + mask: the mask for the src sequence (optional). + warmup: controls selective bypass of of layers; if < 1.0, we will + bypass layers more frequently. + + Shape: + src: (S, N, E). + pos_emb: (N, 2*S-1, E) + mask: (S, S). + src_key_padding_mask: (N, S). + S is the source sequence length, T is the target sequence length, N is the batch size, E is the feature number + + """ + output = src + + for layer_index, mod in enumerate(self.layers): + output = mod( + output, + pos_emb, + src_mask=mask, + src_key_padding_mask=src_key_padding_mask, + warmup=warmup, + ) + + return output + + @torch.jit.export + def chunk_forward( + self, + src: Tensor, + pos_emb: Tensor, + states: List[Tensor], + mask: Optional[Tensor] = None, + src_key_padding_mask: Optional[Tensor] = None, + warmup: float = 1.0, + left_context: int = 0, + right_context: int = 0, + ) -> Tuple[Tensor, List[Tensor]]: + r"""Pass the input through the encoder layers in turn. + + Args: + src: the sequence to the encoder (required). + pos_emb: Positional embedding tensor (required). + states: + The decode states for previous frames which contains the cached data. + It has two elements, the first element is the attn_cache which has + a shape of (encoder_layers, left_context, batch, attention_dim), + the second element is the conv_cache which has a shape of + (encoder_layers, cnn_module_kernel-1, batch, conv_dim). + Note: states will be modified in this function. + mask: the mask for the src sequence (optional). + src_key_padding_mask: the mask for the src keys per batch (optional). + warmup: controls selective bypass of of layers; if < 1.0, we will + bypass layers more frequently. + left_context: + How many previous frames the attention can see in current chunk. + Note: It's not that each individual frame has `left_context` frames + of left context, some have more. + right_context: + How many future frames the attention can see in current chunk. + Note: It's not that each individual frame has `right_context` frames + of right context, some have more. + Shape: + src: (S, N, E). + pos_emb: (N, 2*(S+left_context)-1, E). + mask: (S, S). + src_key_padding_mask: (N, S). + S is the source sequence length, T is the target sequence length, N is the batch size, E is the feature number + + """ + assert not self.training + assert len(states) == 2 + assert states[0].shape == ( + self.num_layers, + left_context, + src.size(1), + src.size(2), + ) + assert states[1].size(0) == self.num_layers + + output = src + + for layer_index, mod in enumerate(self.layers): + cache = [states[0][layer_index], states[1][layer_index]] + output, cache = mod.chunk_forward( + output, + pos_emb, + states=cache, + src_mask=mask, + src_key_padding_mask=src_key_padding_mask, + warmup=warmup, + left_context=left_context, + right_context=right_context, + ) + states[0][layer_index] = cache[0] + states[1][layer_index] = cache[1] + + return output, states + + +class RelPositionalEncoding(torch.nn.Module): + """Relative positional encoding module. + + See : Appendix B in "Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context" + Modified from https://github.com/espnet/espnet/blob/master/espnet/nets/pytorch_backend/transformer/embedding.py + + Args: + d_model: Embedding dimension. + dropout_rate: Dropout rate. + max_len: Maximum input length. + + """ + + def __init__(self, d_model: int, dropout_rate: float, max_len: int = 5000) -> None: + """Construct an PositionalEncoding object.""" + super(RelPositionalEncoding, self).__init__() + if is_jit_tracing(): + # 10k frames correspond to ~100k ms, e.g., 100 seconds, i.e., + # It assumes that the maximum input won't have more than + # 10k frames. + # + # TODO(fangjun): Use torch.jit.script() for this module + max_len = 10000 + + self.d_model = d_model + self.dropout = torch.nn.Dropout(p=dropout_rate) + self.pe = None + self.extend_pe(torch.tensor(0.0).expand(1, max_len)) + + def extend_pe(self, x: Tensor, left_context: int = 0) -> None: + """Reset the positional encodings.""" + x_size_1 = x.size(1) + left_context + if self.pe is not None: + # self.pe contains both positive and negative parts + # the length of self.pe is 2 * input_len - 1 + if self.pe.size(1) >= x_size_1 * 2 - 1: + # Note: TorchScript doesn't implement operator== for torch.Device + if self.pe.dtype != x.dtype or str(self.pe.device) != str(x.device): + self.pe = self.pe.to(dtype=x.dtype, device=x.device) + return + # Suppose `i` means to the position of query vector and `j` means the + # position of key vector. We use position relative positions when keys + # are to the left (i>j) and negative relative positions otherwise (i Tuple[Tensor, Tensor]: + """Add positional encoding. + + Args: + x (torch.Tensor): Input tensor (batch, time, `*`). + left_context (int): left context (in frames) used during streaming decoding. + this is used only in real streaming decoding, in other circumstances, + it MUST be 0. + + Returns: + torch.Tensor: Encoded tensor (batch, time, `*`). + torch.Tensor: Encoded tensor (batch, 2*time-1, `*`). + + """ + self.extend_pe(x, left_context) + x_size_1 = x.size(1) + left_context + pos_emb = self.pe[ + :, + self.pe.size(1) // 2 + - x_size_1 + + 1 : self.pe.size(1) // 2 # noqa E203 + + x.size(1), + ] + return self.dropout(x), self.dropout(pos_emb) + + +class RelPositionMultiheadAttention(nn.Module): + r"""Multi-Head Attention layer with relative position encoding + + See reference: "Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context" + + Args: + embed_dim: total dimension of the model. + num_heads: parallel attention heads. + dropout: a Dropout layer on attn_output_weights. Default: 0.0. + + Examples:: + + >>> rel_pos_multihead_attn = RelPositionMultiheadAttention(embed_dim, num_heads) + >>> attn_output, attn_output_weights = multihead_attn(query, key, value, pos_emb) + """ + + def __init__( + self, + embed_dim: int, + num_heads: int, + dropout: float = 0.0, + ) -> None: + super(RelPositionMultiheadAttention, self).__init__() + self.embed_dim = embed_dim + self.num_heads = num_heads + self.dropout = dropout + self.head_dim = embed_dim // num_heads + assert ( + self.head_dim * num_heads == self.embed_dim + ), "embed_dim must be divisible by num_heads" + + self.in_proj = ScaledLinear(embed_dim, 3 * embed_dim, bias=True) + self.out_proj = ScaledLinear( + embed_dim, embed_dim, bias=True, initial_scale=0.25 + ) + + # linear transformation for positional encoding. + self.linear_pos = ScaledLinear(embed_dim, embed_dim, bias=False) + # these two learnable bias are used in matrix c and matrix d + # as described in "Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context" Section 3.3 + self.pos_bias_u = nn.Parameter(torch.Tensor(num_heads, self.head_dim)) + self.pos_bias_v = nn.Parameter(torch.Tensor(num_heads, self.head_dim)) + self.pos_bias_u_scale = nn.Parameter(torch.zeros(()).detach()) + self.pos_bias_v_scale = nn.Parameter(torch.zeros(()).detach()) + self._reset_parameters() + + def _pos_bias_u(self): + return self.pos_bias_u * self.pos_bias_u_scale.exp() + + def _pos_bias_v(self): + return self.pos_bias_v * self.pos_bias_v_scale.exp() + + def _reset_parameters(self) -> None: + nn.init.normal_(self.pos_bias_u, std=0.01) + nn.init.normal_(self.pos_bias_v, std=0.01) + + def forward( + self, + query: Tensor, + key: Tensor, + value: Tensor, + pos_emb: Tensor, + key_padding_mask: Optional[Tensor] = None, + need_weights: bool = False, + attn_mask: Optional[Tensor] = None, + left_context: int = 0, + ) -> Tuple[Tensor, Optional[Tensor]]: + r""" + Args: + query, key, value: map a query and a set of key-value pairs to an output. + pos_emb: Positional embedding tensor + key_padding_mask: if provided, specified padding elements in the key will + be ignored by the attention. When given a binary mask and a value is True, + the corresponding value on the attention layer will be ignored. When given + a byte mask and a value is non-zero, the corresponding value on the attention + layer will be ignored + need_weights: output attn_output_weights. + attn_mask: 2D or 3D mask that prevents attention to certain positions. A 2D mask will be broadcasted for all + the batches while a 3D mask allows to specify a different mask for the entries of each batch. + left_context (int): left context (in frames) used during streaming decoding. + this is used only in real streaming decoding, in other circumstances, + it MUST be 0. + + Shape: + - Inputs: + - query: :math:`(L, N, E)` where L is the target sequence length, N is the batch size, E is + the embedding dimension. + - key: :math:`(S, N, E)`, where S is the source sequence length, N is the batch size, E is + the embedding dimension. + - value: :math:`(S, N, E)` where S is the source sequence length, N is the batch size, E is + the embedding dimension. + - pos_emb: :math:`(N, 2*L-1, E)` where L is the target sequence length, N is the batch size, E is + the embedding dimension. + - key_padding_mask: :math:`(N, S)` where N is the batch size, S is the source sequence length. + If a ByteTensor is provided, the non-zero positions will be ignored while the position + with the zero positions will be unchanged. If a BoolTensor is provided, the positions with the + value of ``True`` will be ignored while the position with the value of ``False`` will be unchanged. + - attn_mask: 2D mask :math:`(L, S)` where L is the target sequence length, S is the source sequence length. + 3D mask :math:`(N*num_heads, L, S)` where N is the batch size, L is the target sequence length, + S is the source sequence length. attn_mask ensure that position i is allowed to attend the unmasked + positions. If a ByteTensor is provided, the non-zero positions are not allowed to attend + while the zero positions will be unchanged. If a BoolTensor is provided, positions with ``True`` + is not allowed to attend while ``False`` values will be unchanged. If a FloatTensor + is provided, it will be added to the attention weight. + + - Outputs: + - attn_output: :math:`(L, N, E)` where L is the target sequence length, N is the batch size, + E is the embedding dimension. + - attn_output_weights: :math:`(N, L, S)` where N is the batch size, + L is the target sequence length, S is the source sequence length. + """ + return self.multi_head_attention_forward( + query, + key, + value, + pos_emb, + self.embed_dim, + self.num_heads, + self.in_proj.get_weight(), + self.in_proj.get_bias(), + self.dropout, + self.out_proj.get_weight(), + self.out_proj.get_bias(), + training=self.training, + key_padding_mask=key_padding_mask, + need_weights=need_weights, + attn_mask=attn_mask, + left_context=left_context, + ) + + def rel_shift(self, x: Tensor, left_context: int = 0) -> Tensor: + """Compute relative positional encoding. + + Args: + x: Input tensor (batch, head, time1, 2*time1-1+left_context). + time1 means the length of query vector. + left_context (int): left context (in frames) used during streaming decoding. + this is used only in real streaming decoding, in other circumstances, + it MUST be 0. + + Returns: + Tensor: tensor of shape (batch, head, time1, time2) + (note: time2 has the same value as time1, but it is for + the key, while time1 is for the query). + """ + (batch_size, num_heads, time1, n) = x.shape + + time2 = time1 + left_context + if not is_jit_tracing(): + assert ( + n == left_context + 2 * time1 - 1 + ), f"{n} == {left_context} + 2 * {time1} - 1" + + if is_jit_tracing(): + rows = torch.arange(start=time1 - 1, end=-1, step=-1) + cols = torch.arange(time2) + rows = rows.repeat(batch_size * num_heads).unsqueeze(-1) + indexes = rows + cols + + x = x.reshape(-1, n) + x = torch.gather(x, dim=1, index=indexes) + x = x.reshape(batch_size, num_heads, time1, time2) + return x + else: + # Note: TorchScript requires explicit arg for stride() + batch_stride = x.stride(0) + head_stride = x.stride(1) + time1_stride = x.stride(2) + n_stride = x.stride(3) + return x.as_strided( + (batch_size, num_heads, time1, time2), + (batch_stride, head_stride, time1_stride - n_stride, n_stride), + storage_offset=n_stride * (time1 - 1), + ) + + def multi_head_attention_forward( + self, + query: Tensor, + key: Tensor, + value: Tensor, + pos_emb: Tensor, + embed_dim_to_check: int, + num_heads: int, + in_proj_weight: Tensor, + in_proj_bias: Tensor, + dropout_p: float, + out_proj_weight: Tensor, + out_proj_bias: Tensor, + training: bool = True, + key_padding_mask: Optional[Tensor] = None, + need_weights: bool = False, + attn_mask: Optional[Tensor] = None, + left_context: int = 0, + ) -> Tuple[Tensor, Optional[Tensor]]: + r""" + Args: + query, key, value: map a query and a set of key-value pairs to an output. + pos_emb: Positional embedding tensor + embed_dim_to_check: total dimension of the model. + num_heads: parallel attention heads. + in_proj_weight, in_proj_bias: input projection weight and bias. + dropout_p: probability of an element to be zeroed. + out_proj_weight, out_proj_bias: the output projection weight and bias. + training: apply dropout if is ``True``. + key_padding_mask: if provided, specified padding elements in the key will + be ignored by the attention. This is an binary mask. When the value is True, + the corresponding value on the attention layer will be filled with -inf. + need_weights: output attn_output_weights. + attn_mask: 2D or 3D mask that prevents attention to certain positions. A 2D mask will be broadcasted for all + the batches while a 3D mask allows to specify a different mask for the entries of each batch. + left_context (int): left context (in frames) used during streaming decoding. + this is used only in real streaming decoding, in other circumstances, + it MUST be 0. + + Shape: + Inputs: + - query: :math:`(L, N, E)` where L is the target sequence length, N is the batch size, E is + the embedding dimension. + - key: :math:`(S, N, E)`, where S is the source sequence length, N is the batch size, E is + the embedding dimension. + - value: :math:`(S, N, E)` where S is the source sequence length, N is the batch size, E is + the embedding dimension. + - pos_emb: :math:`(N, 2*L-1, E)` or :math:`(1, 2*L-1, E)` where L is the target sequence + length, N is the batch size, E is the embedding dimension. + - key_padding_mask: :math:`(N, S)` where N is the batch size, S is the source sequence length. + If a ByteTensor is provided, the non-zero positions will be ignored while the zero positions + will be unchanged. If a BoolTensor is provided, the positions with the + value of ``True`` will be ignored while the position with the value of ``False`` will be unchanged. + - attn_mask: 2D mask :math:`(L, S)` where L is the target sequence length, S is the source sequence length. + 3D mask :math:`(N*num_heads, L, S)` where N is the batch size, L is the target sequence length, + S is the source sequence length. attn_mask ensures that position i is allowed to attend the unmasked + positions. If a ByteTensor is provided, the non-zero positions are not allowed to attend + while the zero positions will be unchanged. If a BoolTensor is provided, positions with ``True`` + are not allowed to attend while ``False`` values will be unchanged. If a FloatTensor + is provided, it will be added to the attention weight. + + Outputs: + - attn_output: :math:`(L, N, E)` where L is the target sequence length, N is the batch size, + E is the embedding dimension. + - attn_output_weights: :math:`(N, L, S)` where N is the batch size, + L is the target sequence length, S is the source sequence length. + """ + + tgt_len, bsz, embed_dim = query.size() + if not is_jit_tracing(): + assert embed_dim == embed_dim_to_check + assert key.size(0) == value.size(0) and key.size(1) == value.size(1) + + head_dim = embed_dim // num_heads + if not is_jit_tracing(): + assert ( + head_dim * num_heads == embed_dim + ), "embed_dim must be divisible by num_heads" + + scaling = float(head_dim) ** -0.5 + + if torch.equal(query, key) and torch.equal(key, value): + # self-attention + q, k, v = nn.functional.linear(query, in_proj_weight, in_proj_bias).chunk( + 3, dim=-1 + ) + + elif torch.equal(key, value): + # encoder-decoder attention + # This is inline in_proj function with in_proj_weight and in_proj_bias + _b = in_proj_bias + _start = 0 + _end = embed_dim + _w = in_proj_weight[_start:_end, :] + if _b is not None: + _b = _b[_start:_end] + q = nn.functional.linear(query, _w, _b) + + # This is inline in_proj function with in_proj_weight and in_proj_bias + _b = in_proj_bias + _start = embed_dim + _end = None + _w = in_proj_weight[_start:, :] + if _b is not None: + _b = _b[_start:] + k, v = nn.functional.linear(key, _w, _b).chunk(2, dim=-1) + + else: + # This is inline in_proj function with in_proj_weight and in_proj_bias + _b = in_proj_bias + _start = 0 + _end = embed_dim + _w = in_proj_weight[_start:_end, :] + if _b is not None: + _b = _b[_start:_end] + q = nn.functional.linear(query, _w, _b) + + # This is inline in_proj function with in_proj_weight and in_proj_bias + _b = in_proj_bias + _start = embed_dim + _end = embed_dim * 2 + _w = in_proj_weight[_start:_end, :] + if _b is not None: + _b = _b[_start:_end] + k = nn.functional.linear(key, _w, _b) + + # This is inline in_proj function with in_proj_weight and in_proj_bias + _b = in_proj_bias + _start = embed_dim * 2 + _end = None + _w = in_proj_weight[_start:, :] + if _b is not None: + _b = _b[_start:] + v = nn.functional.linear(value, _w, _b) + + if attn_mask is not None: + assert ( + attn_mask.dtype == torch.float32 + or attn_mask.dtype == torch.float64 + or attn_mask.dtype == torch.float16 + or attn_mask.dtype == torch.uint8 + or attn_mask.dtype == torch.bool + ), "Only float, byte, and bool types are supported for attn_mask, not {}".format( + attn_mask.dtype + ) + if attn_mask.dtype == torch.uint8: + warnings.warn( + "Byte tensor for attn_mask is deprecated. Use bool tensor instead." + ) + attn_mask = attn_mask.to(torch.bool) + + if attn_mask.dim() == 2: + attn_mask = attn_mask.unsqueeze(0) + if list(attn_mask.size()) != [1, query.size(0), key.size(0)]: + raise RuntimeError("The size of the 2D attn_mask is not correct.") + elif attn_mask.dim() == 3: + if list(attn_mask.size()) != [ + bsz * num_heads, + query.size(0), + key.size(0), + ]: + raise RuntimeError("The size of the 3D attn_mask is not correct.") + else: + raise RuntimeError( + "attn_mask's dimension {} is not supported".format(attn_mask.dim()) + ) + # attn_mask's dim is 3 now. + + # convert ByteTensor key_padding_mask to bool + if key_padding_mask is not None and key_padding_mask.dtype == torch.uint8: + warnings.warn( + "Byte tensor for key_padding_mask is deprecated. Use bool tensor instead." + ) + key_padding_mask = key_padding_mask.to(torch.bool) + + q = (q * scaling).contiguous().view(tgt_len, bsz, num_heads, head_dim) + k = k.contiguous().view(-1, bsz, num_heads, head_dim) + v = v.contiguous().view(-1, bsz * num_heads, head_dim).transpose(0, 1) + + src_len = k.size(0) + + if key_padding_mask is not None and not is_jit_tracing(): + assert key_padding_mask.size(0) == bsz, "{} == {}".format( + key_padding_mask.size(0), bsz + ) + assert key_padding_mask.size(1) == src_len, "{} == {}".format( + key_padding_mask.size(1), src_len + ) + + q = q.transpose(0, 1) # (batch, time1, head, d_k) + + pos_emb_bsz = pos_emb.size(0) + if not is_jit_tracing(): + assert pos_emb_bsz in (1, bsz) # actually it is 1 + + p = self.linear_pos(pos_emb).view(pos_emb_bsz, -1, num_heads, head_dim) + # (batch, 2*time1, head, d_k) --> (batch, head, d_k, 2*time -1) + p = p.permute(0, 2, 3, 1) + + q_with_bias_u = (q + self._pos_bias_u()).transpose( + 1, 2 + ) # (batch, head, time1, d_k) + + q_with_bias_v = (q + self._pos_bias_v()).transpose( + 1, 2 + ) # (batch, head, time1, d_k) + + # compute attention score + # first compute matrix a and matrix c + # as described in "Transformer-XL: Attentive Language Models Beyond a Fixed-Length Context" Section 3.3 + k = k.permute(1, 2, 3, 0) # (batch, head, d_k, time2) + matrix_ac = torch.matmul(q_with_bias_u, k) # (batch, head, time1, time2) + + # compute matrix b and matrix d + matrix_bd = torch.matmul(q_with_bias_v, p) # (batch, head, time1, 2*time1-1) + matrix_bd = self.rel_shift(matrix_bd, left_context) + + attn_output_weights = matrix_ac + matrix_bd # (batch, head, time1, time2) + + attn_output_weights = attn_output_weights.view(bsz * num_heads, tgt_len, -1) + + if not is_jit_tracing(): + assert list(attn_output_weights.size()) == [ + bsz * num_heads, + tgt_len, + src_len, + ] + + if attn_mask is not None: + if attn_mask.dtype == torch.bool: + attn_output_weights.masked_fill_(attn_mask, float("-inf")) + else: + attn_output_weights += attn_mask + + if key_padding_mask is not None: + attn_output_weights = attn_output_weights.view( + bsz, num_heads, tgt_len, src_len + ) + attn_output_weights = attn_output_weights.masked_fill( + key_padding_mask.unsqueeze(1).unsqueeze(2), + float("-inf"), + ) + attn_output_weights = attn_output_weights.view( + bsz * num_heads, tgt_len, src_len + ) + + attn_output_weights = nn.functional.softmax(attn_output_weights, dim=-1) + + # If we are using dynamic_chunk_training and setting a limited + # num_left_chunks, the attention may only see the padding values which + # will also be masked out by `key_padding_mask`, at this circumstances, + # the whole column of `attn_output_weights` will be `-inf` + # (i.e. be `nan` after softmax), so, we fill `0.0` at the masking + # positions to avoid invalid loss value below. + if ( + attn_mask is not None + and attn_mask.dtype == torch.bool + and key_padding_mask is not None + ): + if attn_mask.size(0) != 1: + attn_mask = attn_mask.view(bsz, num_heads, tgt_len, src_len) + combined_mask = attn_mask | key_padding_mask.unsqueeze(1).unsqueeze(2) + else: + # attn_mask.shape == (1, tgt_len, src_len) + combined_mask = attn_mask.unsqueeze(0) | key_padding_mask.unsqueeze( + 1 + ).unsqueeze(2) + + attn_output_weights = attn_output_weights.view( + bsz, num_heads, tgt_len, src_len + ) + attn_output_weights = attn_output_weights.masked_fill(combined_mask, 0.0) + attn_output_weights = attn_output_weights.view( + bsz * num_heads, tgt_len, src_len + ) + + attn_output_weights = nn.functional.dropout( + attn_output_weights, p=dropout_p, training=training + ) + + attn_output = torch.bmm(attn_output_weights, v) + + if not is_jit_tracing(): + assert list(attn_output.size()) == [ + bsz * num_heads, + tgt_len, + head_dim, + ] + + attn_output = ( + attn_output.transpose(0, 1).contiguous().view(tgt_len, bsz, embed_dim) + ) + attn_output = nn.functional.linear(attn_output, out_proj_weight, out_proj_bias) + + if need_weights: + # average attention weights over heads + attn_output_weights = attn_output_weights.view( + bsz, num_heads, tgt_len, src_len + ) + return attn_output, attn_output_weights.sum(dim=1) / num_heads + else: + return attn_output, None + + +class ConvolutionModule(nn.Module): + """ConvolutionModule in Conformer model. + Modified from https://github.com/espnet/espnet/blob/master/espnet/nets/pytorch_backend/conformer/convolution.py + + Args: + channels (int): The number of channels of conv layers. + kernel_size (int): Kernerl size of conv layers. + bias (bool): Whether to use bias in conv layers (default=True). + causal (bool): Whether to use causal convolution. + """ + + def __init__( + self, + channels: int, + kernel_size: int, + bias: bool = True, + causal: bool = False, + ) -> None: + """Construct an ConvolutionModule object.""" + super(ConvolutionModule, self).__init__() + # kernerl_size should be a odd number for 'SAME' padding + assert (kernel_size - 1) % 2 == 0 + self.causal = causal + + self.pointwise_conv1 = ScaledConv1d( + channels, + 2 * channels, + kernel_size=1, + stride=1, + padding=0, + bias=bias, + ) + + # after pointwise_conv1 we put x through a gated linear unit (nn.functional.glu). + # For most layers the normal rms value of channels of x seems to be in the range 1 to 4, + # but sometimes, for some reason, for layer 0 the rms ends up being very large, + # between 50 and 100 for different channels. This will cause very peaky and + # sparse derivatives for the sigmoid gating function, which will tend to make + # the loss function not learn effectively. (for most layers the average absolute values + # are in the range 0.5..9.0, and the average p(x>0), i.e. positive proportion, + # at the output of pointwise_conv1.output is around 0.35 to 0.45 for different + # layers, which likely breaks down as 0.5 for the "linear" half and + # 0.2 to 0.3 for the part that goes into the sigmoid. The idea is that if we + # constrain the rms values to a reasonable range via a constraint of max_abs=10.0, + # it will be in a better position to start learning something, i.e. to latch onto + # the correct range. + self.deriv_balancer1 = ActivationBalancer( + channel_dim=1, max_abs=10.0, min_positive=0.05, max_positive=1.0 + ) + + self.lorder = kernel_size - 1 + padding = (kernel_size - 1) // 2 + if self.causal: + padding = 0 + + self.depthwise_conv = ScaledConv1d( + channels, + channels, + kernel_size, + stride=1, + padding=padding, + groups=channels, + bias=bias, + ) + + self.deriv_balancer2 = ActivationBalancer( + channel_dim=1, min_positive=0.05, max_positive=1.0 + ) + + self.activation = DoubleSwish() + + self.pointwise_conv2 = ScaledConv1d( + channels, + channels, + kernel_size=1, + stride=1, + padding=0, + bias=bias, + initial_scale=0.25, + ) + + def forward( + self, + x: Tensor, + cache: Optional[Tensor] = None, + right_context: int = 0, + src_key_padding_mask: Optional[Tensor] = None, + ) -> Tuple[Tensor, Tensor]: + """Compute convolution module. + + Args: + x: Input tensor (#time, batch, channels). + cache: The cache of depthwise_conv, only used in real streaming + decoding. + right_context: + How many future frames the attention can see in current chunk. + Note: It's not that each individual frame has `right_context` frames + src_key_padding_mask: the mask for the src keys per batch (optional). + of right context, some have more. + + Returns: + If cache is None return the output tensor (#time, batch, channels). + If cache is not None, return a tuple of Tensor, the first one is + the output tensor (#time, batch, channels), the second one is the + new cache for next chunk (#kernel_size - 1, batch, channels). + + """ + # exchange the temporal dimension and the feature dimension + x = x.permute(1, 2, 0) # (#batch, channels, time). + + # GLU mechanism + x = self.pointwise_conv1(x) # (batch, 2*channels, time) + + x = self.deriv_balancer1(x) + x = nn.functional.glu(x, dim=1) # (batch, channels, time) + + # 1D Depthwise Conv + if src_key_padding_mask is not None: + x.masked_fill_(src_key_padding_mask.unsqueeze(1).expand_as(x), 0.0) + if self.causal and self.lorder > 0: + if cache is None: + # Make depthwise_conv causal by + # manualy padding self.lorder zeros to the left + x = nn.functional.pad(x, (self.lorder, 0), "constant", 0.0) + else: + assert not self.training, "Cache should be None in training time" + assert cache.size(0) == self.lorder + x = torch.cat([cache.permute(1, 2, 0), x], dim=2) + if right_context > 0: + cache = x.permute(2, 0, 1)[ + -(self.lorder + right_context) : (-right_context), # noqa + ..., + ] + else: + cache = x.permute(2, 0, 1)[-self.lorder :, ...] # noqa + x = self.depthwise_conv(x) + + x = self.deriv_balancer2(x) + x = self.activation(x) + + x = self.pointwise_conv2(x) # (batch, channel, time) + + # torch.jit.script requires return types be the same as annotated above + if cache is None: + cache = torch.empty(0) + + return x.permute(2, 0, 1), cache + + +class Conv2dSubsampling(nn.Module): + """Convolutional 2D subsampling (to 1/4 length). + + Convert an input of shape (N, T, idim) to an output + with shape (N, T', odim), where + T' = ((T-1)//2 - 1)//2, which approximates T' == T//4 + + It is based on + https://github.com/espnet/espnet/blob/master/espnet/nets/pytorch_backend/transformer/subsampling.py # noqa + """ + + def __init__( + self, + in_channels: int, + out_channels: int, + layer1_channels: int = 8, + layer2_channels: int = 32, + layer3_channels: int = 128, + ) -> None: + """ + Args: + in_channels: + Number of channels in. The input shape is (N, T, in_channels). + Caution: It requires: T >=7, in_channels >=7 + out_channels + Output dim. The output shape is (N, ((T-1)//2 - 1)//2, out_channels) + layer1_channels: + Number of channels in layer1 + layer1_channels: + Number of channels in layer2 + """ + assert in_channels >= 7 + super().__init__() + + self.conv = nn.Sequential( + ScaledConv2d( + in_channels=1, + out_channels=layer1_channels, + kernel_size=3, + padding=1, + ), + ActivationBalancer(channel_dim=1), + DoubleSwish(), + ScaledConv2d( + in_channels=layer1_channels, + out_channels=layer2_channels, + kernel_size=3, + stride=2, + ), + ActivationBalancer(channel_dim=1), + DoubleSwish(), + ScaledConv2d( + in_channels=layer2_channels, + out_channels=layer3_channels, + kernel_size=3, + stride=2, + ), + ActivationBalancer(channel_dim=1), + DoubleSwish(), + ) + self.out = ScaledLinear( + layer3_channels * (((in_channels - 1) // 2 - 1) // 2), out_channels + ) + # set learn_eps=False because out_norm is preceded by `out`, and `out` + # itself has learned scale, so the extra degree of freedom is not + # needed. + self.out_norm = BasicNorm(out_channels, learn_eps=False) + # constrain median of output to be close to zero. + self.out_balancer = ActivationBalancer( + channel_dim=-1, min_positive=0.45, max_positive=0.55 + ) + + def forward(self, x: torch.Tensor) -> torch.Tensor: + """Subsample x. + + Args: + x: + Its shape is (N, T, idim). + + Returns: + Return a tensor of shape (N, ((T-1)//2 - 1)//2, odim) + """ + # On entry, x is (N, T, idim) + x = x.unsqueeze(1) # (N, T, idim) -> (N, 1, T, idim) i.e., (N, C, H, W) + x = self.conv(x) + # Now x is of shape (N, odim, ((T-1)//2 - 1)//2, ((idim-1)//2 - 1)//2) + b, c, t, f = x.size() + x = self.out(x.transpose(1, 2).contiguous().view(b, t, c * f)) + # Now x is of shape (N, ((T-1)//2 - 1))//2, odim) + x = self.out_norm(x) + x = self.out_balancer(x) + return x + + +if __name__ == "__main__": + torch.set_num_threads(1) + torch.set_num_interop_threads(1) + feature_dim = 50 + c = Conformer(num_features=feature_dim, d_model=128, nhead=4) + batch_size = 5 + seq_len = 20 + # Just make sure the forward pass runs. + f = c( + torch.randn(batch_size, seq_len, feature_dim), + torch.full((batch_size,), seq_len, dtype=torch.int64), + warmup=0.5, + )