#!/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 import itertools from typing import List, Optional, Tuple, Union import logging import torch import random from encoder_interface import EncoderInterface from scaling import ( ActivationBalancer, BasicNorm, DoubleSwish, ScaledConv1d, ScaledLinear, # not as in other dirs.. just scales down initial parameter values. ) from torch import Tensor, nn from icefall.utils import make_pad_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): embedding dimension nhead (int): number of head dim_feedforward (int): feedforward dimention num_encoder_layers (int): number of encoder layers dropout (float): dropout rate cnn_module_kernel (int): Kernel size of convolution module vgg_frontend (bool): whether to use vgg frontend. warmup_batches (float): number of batches to warm up over """ def __init__( self, num_features: int, subsampling_factor: int = 4, conformer_subsampling_factor: int = 4, d_model: Tuple[int] = (384, 384), encoder_unmasked_dim: int = 256, nhead: Tuple[int] = (8, 8), feedforward_dim: Tuple[int] = (1536, 2048), num_encoder_layers: Tuple[int] = (12, 12), dropout: float = 0.1, cnn_module_kernel: Tuple[int] = (31, 31), warmup_batches: float = 4000.0, ) -> None: super(Conformer, self).__init__() self.num_features = num_features self.subsampling_factor = subsampling_factor self.encoder_unmasked_dim = encoder_unmasked_dim assert 0 < d_model[0] <= d_model[1] self.d_model = d_model self.conformer_subsampling_factor = conformer_subsampling_factor assert encoder_unmasked_dim <= d_model[0] and encoder_unmasked_dim <= d_model[1] 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[0], dropout=dropout) encoder_layer1 = ConformerEncoderLayer( d_model[0], nhead[0], feedforward_dim[0], dropout, cnn_module_kernel[0], ) # for the first third of the warmup period, we let the Conv2dSubsampling # layer learn something. then start warmup up the first and then the second # encoder. self.encoder1 = ConformerEncoder( encoder_layer1, num_encoder_layers[0], dropout, warmup_begin=warmup_batches / 3, warmup_end=warmup_batches * 2 / 3, ) encoder_layer2 = ConformerEncoderLayer( d_model[1], nhead[1], feedforward_dim[1], dropout, cnn_module_kernel[1], ) self.encoder2 = DownsampledConformerEncoder( ConformerEncoder( encoder_layer2, num_encoder_layers[1], dropout, warmup_begin=warmup_batches * 2 / 3, warmup_end=warmup_batches, ), input_dim=d_model[0], output_dim=d_model[1], downsample=conformer_subsampling_factor, ) self.out_combiner = SimpleCombiner(d_model[0], d_model[1]) def get_feature_mask( self, x: torch.Tensor) -> Tuple[Union[float, Tensor], Union[float, Tensor]]: """ In eval mode, returns 1.0; in training mode, returns two randomized feature masks for the 1st and second encoders (which may run at different frame rates). On e.g. 15% of frames, these masks will zero out all enocder dims larger than some supplied number, e.g. >256, so in effect on those frames we are using a smaller encoer dim. We generate the random masks at this level because we want the 2 masks to 'agree' all the way up the encoder stack. This will mean that the 1st mask will have mask values repeated self.conformer_subsampling_factor times. Args: x: the embeddings (needed for the shape and dtype and device), of shape (num_frames, batch_size, d_model0) """ if not self.training: return 1.0, 1.0 d_model0, d_model1 = self.d_model (num_frames0, batch_size, _d_model0) = x.shape assert d_model0 == _d_model0 ds = self.conformer_subsampling_factor num_frames1 = ((num_frames0 + ds - 1) // ds) # on this proportion of the frames, drop out the extra features above # self.encoder_unmasked_dim. feature_mask_dropout_prob = 0.15 # we only apply the random frame masking on 90% of sequences; we leave the remaining 10% # un-masked so that the model has seen un-masked data. sequence_mask_dropout_prob = 0.9 # frame_mask is 0 with probability `feature_mask_dropout_prob` # frame_mask1 shape: (num_frames1, batch_size, 1) frame_mask1 = torch.logical_or( torch.rand(num_frames1, batch_size, 1, device=x.device) > feature_mask_dropout_prob, torch.rand(1, batch_size, 1, device=x.device) > sequence_mask_dropout_prob).to(x.dtype) feature_mask1 = torch.ones(num_frames1, batch_size, self.d_model[1], dtype=x.dtype, device=x.device) feature_mask1[:, :, self.encoder_unmasked_dim:] *= frame_mask1 # frame_mask0 shape: (num_frames0, batch_size, 1) frame_mask0 = frame_mask1.unsqueeze(1).expand(num_frames1, ds, batch_size, 1).reshape( num_frames1 * ds, batch_size, 1)[:num_frames0] feature_mask0 = torch.ones(num_frames0, batch_size, self.d_model[0], dtype=x.dtype, device=x.device) feature_mask0[:, :, self.encoder_unmasked_dim:] *= frame_mask0 return feature_mask0, feature_mask1 def forward( self, x: torch.Tensor, x_lens: torch.Tensor, ) -> 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. 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 = x.permute(1, 0, 2) # (N, T, C) -> (T, N, C) with warnings.catch_warnings(): warnings.simplefilter("ignore") # Caution: We assume the subsampling factor is 4! lengths = ((x_lens - 1) // 2 - 1) // 2 assert x.size(0) == lengths.max().item() mask = make_pad_mask(lengths) feature_mask0, feature_mask1 = self.get_feature_mask(x) # x1: x1 = self.encoder1( x, feature_mask=feature_mask0, src_key_padding_mask=mask, ) # (T, N, C) where C == d_model[0] x2 = self.encoder2( x1, feature_mask=feature_mask1, src_key_padding_mask=mask, ) # (T, N, C) where C == d_model[1] x = self.out_combiner(x1, x2) x = x.permute(1, 0, 2) # (T, N, C) ->(N, T, C) return x, lengths 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). feedforward_dim: 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. 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, feedforward_dim: int = 2048, dropout: float = 0.1, cnn_module_kernel: int = 31, ) -> None: super(ConformerEncoderLayer, self).__init__() self.d_model = d_model self.self_attn = RelPositionMultiheadAttention( d_model, nhead, dropout=dropout, ) self.feed_forward1 = FeedforwardModule(d_model, feedforward_dim, dropout) self.feed_forward2 = FeedforwardModule(d_model, feedforward_dim, dropout) self.feed_forward3 = FeedforwardModule(d_model, feedforward_dim, dropout) self.conv_module1 = ConvolutionModule(d_model, cnn_module_kernel) self.conv_module2 = ConvolutionModule(d_model, cnn_module_kernel) self.norm_final = BasicNorm(d_model) self.bypass_scale = nn.Parameter(torch.tensor(0.5)) # try to ensure the output is close to zero-mean (or at least, zero-median). self.balancer = ActivationBalancer( d_model, channel_dim=-1, min_positive=0.45, max_positive=0.55, max_abs=6.0, max_var_per_eig=0.2, ) def forward( self, src: Tensor, pos_emb: Tensor, attn_scores_in: Optional[Tensor] = None, src_mask: Optional[Tensor] = None, src_key_padding_mask: Optional[Tensor] = None, ) -> Tuple[Tensor, Tensor]: """ Pass the input through the encoder layer. Args: src: the sequence to the encoder layer (required). pos_emb: Positional embedding tensor (required). attn_scores_in: something with the dimension fo attention weights (bsz, len, len, num_heads) that is passed from layer to layer. src_mask: the mask for the src sequence (optional). src_key_padding_mask: the mask for the src keys per batch (optional). batch_split: if not None, this layer will only be applied to 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 # macaron style feed forward module src = src + self.feed_forward1(src) # multi-headed self-attention module src_att, attn_weights, attn_scores_out = self.self_attn( src, pos_emb=pos_emb, attn_scores_in=attn_scores_in, attn_mask=src_mask, key_padding_mask=src_key_padding_mask, ) src = src + src_att # convolution module src = src + self.conv_module1(src, src_key_padding_mask=src_key_padding_mask) src = src + self.feed_forward2(src) src = src + self.self_attn.forward2(src, attn_weights) src = src + self.conv_module2(src, src_key_padding_mask=src_key_padding_mask) src = src + self.feed_forward3(src) src = self.norm_final(self.balancer(src)) delta = src - src_orig bypass_scale = self.bypass_scale if random.random() > 0.1: bypass_scale = bypass_scale.clamp(min=0.1, max=1.0) src = src_orig + delta * self.bypass_scale return src, attn_scores_out 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) >>> out = conformer_encoder(src) """ def __init__( self, encoder_layer: nn.Module, num_layers: int, dropout: float, warmup_begin: float, warmup_end: float ) -> None: super().__init__() # keep track of how many times forward() has been called, for purposes # of warmup. do this with a floating-point count because integer counts # can fail to survive model averaging. initialize with a smallish # random number so that different encoders use different random seeds in # shared_rng get_layers_to_drop() while using the same random seeds # across jobs. self.register_buffer('warmup_count', torch.tensor(float(10.0 * random.random()))) self.warmup_begin = warmup_begin self.warmup_end = warmup_end self.encoder_pos = RelPositionalEncoding(encoder_layer.d_model, dropout) self.layers = nn.ModuleList( [copy.deepcopy(encoder_layer) for i in range(num_layers)] ) self.num_layers = num_layers assert 0 <= warmup_begin <= warmup_end delta = (1. / num_layers) * (warmup_end - warmup_begin) cur_begin = warmup_begin for i in range(num_layers): self.layers[i].warmup_begin = cur_begin cur_begin += delta self.layers[i].warmup_end = cur_begin def get_warmup_count(self) -> float: """ Returns a value that reflects how many times this function has been called in training mode. """ ans = self.warmup_count.item() if self.training: if ans > 1000000.0: # this ensures that as the number of batches gets large, the warmup count cycles rather # than getting stuck at the smallest floating point value x such that x + 1 == x. # this is necessary because get_layers_to_drop() relies on the warmup count changing # on every batch. next_count = 500000.0 else: next_count = ans + 1.0 self.warmup_count.fill_(next_count) return ans def get_layers_to_drop(self, rnd_seed: int, warmup_count: float): num_layers = len(self.layers) warmup_begin = self.warmup_begin warmup_end = self.warmup_end def get_layerdrop_prob(layer: int) -> float: layer_warmup_delta = (warmup_end - warmup_begin) / num_layers layer_warmup_begin = warmup_begin + layer * layer_warmup_delta initial_layerdrop_prob = 0.5 final_layerdrop_prob = 0.075 layer_warmup_end = layer_warmup_begin + layer_warmup_delta if warmup_count < layer_warmup_begin: return initial_layerdrop_prob elif warmup_count > layer_warmup_end: return final_layerdrop_prob else: # linearly interpolate t = (warmup_count - layer_warmup_begin) / layer_warmup_end assert 0.0 <= t < 1.001 return initial_layerdrop_prob + t * (final_layerdrop_prob - initial_layerdrop_prob) ans = set() if not self.training: return ans shared_rng = random.Random(int(warmup_count * 1000)) independent_rng = random.Random(rnd_seed) layerdrop_probs = [ get_layerdrop_prob(i) for i in range(num_layers) ] tot = sum(layerdrop_probs) # Instead of drawing the samples independently, we first randomly decide # how many layers to drop out, using the same random number generator between # jobs so that all jobs drop out the same number (this is for speed). # Then we use an approximate approach to drop out the individual layers # with their specified probs while reaching this exact target. num_to_drop = int(tot) + int(shared_rng.random() < (tot - int(tot))) layers = list(range(num_layers)) independent_rng.shuffle(layers) # go through the shuffled layers until we get the required number of samples. if num_to_drop > 0: for layer in itertools.cycle(layers): if independent_rng.random() < layerdrop_probs[layer]: ans.add(layer) if len(ans) == num_to_drop: break if shared_rng.random() < 0.005 or __name__ == "__main__": logging.info(f"warmup_begin={warmup_begin}, warmup_end={warmup_end}, warmup_count={warmup_count:.1f}, num_to_drop={num_to_drop}, layers_to_drop={ans}") return ans def forward( self, src: Tensor, feature_mask: Union[Tensor, float] = 1.0, mask: Optional[Tensor] = None, src_key_padding_mask: Optional[Tensor] = None, ) -> Tensor: r"""Pass the input through the encoder layers in turn. Args: src: the sequence to the encoder (required). feature_mask: something that broadcasts with src, that we'll multiply `src` by at every layer. mask: the mask for the src sequence (optional). src_key_padding_mask: the mask for the src keys per batch (optional). 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 Returns: (x, x_no_combine), both of shape (S, N, E) """ pos_emb = self.encoder_pos(src) output = src outputs = [] attn_scores = None rnd_seed = src.numel() + random.randint(0, 1000) layers_to_drop = self.get_layers_to_drop(rnd_seed, self.get_warmup_count()) output = output * feature_mask for i, mod in enumerate(self.layers): if i in layers_to_drop: continue output, attn_scores = mod( output, pos_emb, attn_scores, src_mask=mask, src_key_padding_mask=src_key_padding_mask, ) output = output * feature_mask return output class DownsampledConformerEncoder(nn.Module): r""" DownsampledConformerEncoder is a conformer encoder evaluated at a reduced frame rate, after convolutional downsampling, and then upsampled again at the output so that the output has the same shape as the input. """ def __init__(self, encoder: nn.Module, input_dim: int, output_dim: int, downsample: int): super(DownsampledConformerEncoder, self).__init__() self.downsample_factor = downsample self.downsample = AttentionDownsample(input_dim, output_dim, downsample) self.encoder = encoder self.upsample = SimpleUpsample(output_dim, downsample) def forward(self, src: Tensor, feature_mask: Union[Tensor, float] = 1.0, mask: Optional[Tensor] = None, src_key_padding_mask: Optional[Tensor] = None, ) -> Tuple[Tensor, Tensor]: r"""Downsample, go through encoder, upsample. Args: src: the sequence to the encoder (required). feature_mask: something that broadcasts with src, that we'll multiply `src` by at every layer. feature_mask is expected to be already downsampled by self.downsample_factor. mask: the mask for the src sequence (optional). CAUTION: we need to downsample this, if we are to support it. Won't work correctly yet. src_key_padding_mask: the mask for the src keys per batch (optional). Shape: src: (S, N, 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 Returns: output of shape (S, N, F) where F is the number of output features (output_dim to constructor) """ src_orig = src src = self.downsample(src) ds = self.downsample_factor if mask is not None: mask = mask[::ds,::ds] if src_key_padding_mask is not None: src_key_padding_mask = src_key_padding_mask[::ds] src = self.encoder( src, feature_mask=feature_mask, mask=mask, src_key_padding_mask=mask, ) src = self.upsample(src) # remove any extra frames that are not a multiple of downsample_factor src = src[:src_orig.shape[0]] return src class AttentionDownsample(torch.nn.Module): """ Does downsampling with attention, by weighted sum, and a projection.. """ def __init__(self, in_channels: int, out_channels: int, downsample: int): """ Require out_channels > in_channels. """ super(AttentionDownsample, self).__init__() self.query = nn.Parameter(torch.randn(in_channels) * (in_channels ** -0.5)) # fill in the extra dimensions with a projection of the input if out_channels > in_channels: self.extra_proj = nn.Linear(in_channels * downsample, out_channels - in_channels, bias=False) else: self.extra_proj = None self.downsample = downsample def forward(self, src: Tensor) -> Tensor: """ x: (seq_len, batch_size, in_channels) Returns a tensor of shape ( (seq_len+downsample-1)//downsample, batch_size, out_channels) """ (seq_len, batch_size, in_channels) = src.shape ds = self.downsample d_seq_len = (seq_len + ds - 1) // ds src_orig = src # Pad to an exact multiple of self.downsample if seq_len != d_seq_len * ds: # right-pad src, repeating the last element. pad = d_seq_len * ds - seq_len src_extra = src[src.shape[0]-1:].expand(pad, src.shape[1], src.shape[2]) src = torch.cat((src, src_extra), dim=0) assert src.shape[0] == d_seq_len * ds src = src.reshape(d_seq_len, ds, batch_size, in_channels) scores = (src * self.query).sum(dim=-1, keepdim=True) weights = scores.softmax(dim=1) # ans1 is the first `in_channels` channels of the output ans = (src * weights).sum(dim=1) src = src.permute(0, 2, 1, 3).reshape(d_seq_len, batch_size, ds * in_channels) if self.extra_proj is not None: ans2 = self.extra_proj(src) ans = torch.cat((ans, ans2), dim=2) return ans class SimpleUpsample(torch.nn.Module): """ A very simple form of upsampling that mostly just repeats the input, but also adds a position-specific bias. """ def __init__(self, num_channels: int, upsample: int): super(SimpleUpsample, self).__init__() self.bias = nn.Parameter(torch.randn(upsample, num_channels) * 0.01) def forward(self, src: Tensor) -> Tensor: """ x: (seq_len, batch_size, num_channels) Returns a tensor of shape ( (seq_len*upsample), batch_size, num_channels) """ upsample = self.bias.shape[0] (seq_len, batch_size, num_channels) = src.shape src = src.unsqueeze(1).expand(seq_len, upsample, batch_size, num_channels) src = src + self.bias.unsqueeze(1) src = src.reshape(seq_len * upsample, batch_size, num_channels) return src class SimpleCombiner(torch.nn.Module): """ A very simple way of combining 2 vectors of 2 different dims, via a learned weighted combination in the shared part of the dim. Args: dim1: the dimension of the first input, e.g. 256 dim2: the dimension of the second input, e.g. 384. Require dim2 >= dim1. The output will have the same dimension as dim2. """ def __init__(self, dim1: int, dim2: int): super(SimpleCombiner, self).__init__() assert dim2 >= dim1 self.to_weight1 = nn.Parameter(torch.randn(dim1) * 0.01) self.to_weight2 = nn.Parameter(torch.randn(dim2) * 0.01) def forward(self, src1: Tensor, src2: Tensor) -> Tensor: """ src1: (*, dim1) src2: (*, dim2) Returns: a tensor of shape (*, dim2) """ assert src1.shape[:-1] == src2.shape[:-1] dim1 = src1.shape[-1] dim2 = src2.shape[-1] weight1 = (src1 * self.to_weight1).sum(dim=-1, keepdim=True) weight2 = (src2 * self.to_weight2).sum(dim=-1, keepdim=True) weight = (weight1 + weight2).sigmoid() src2_part1 = src2[...,:dim1] part1 = src1 * weight + src2_part1 * (1.0 - weight) part2 = src2[...,dim1:] return torch.cat((part1, part2), dim=-1) 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 a PositionalEncoding object.""" super(RelPositionalEncoding, self).__init__() self.d_model = d_model self.dropout = torch.nn.Dropout(dropout_rate) self.pe = None self.extend_pe(torch.tensor(0.0).expand(1, max_len)) def extend_pe(self, x: Tensor) -> None: """Reset the positional encodings.""" 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(0) * 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 vecotr 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 (time, batch, `*`). Returns: torch.Tensor: Encoded tensor (batch, time, `*`). torch.Tensor: Encoded tensor (batch, 2*time-1, `*`). """ self.extend_pe(x) pos_emb = self.pe[ :, self.pe.size(1) // 2 - x.size(0) + 1 : self.pe.size(1) // 2 # noqa E203 + x.size(0), ] return 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 * 2) assert ( self.head_dim * num_heads == self.embed_dim // 2 ), "embed_dim//2 must be divisible by num_heads" self.in_proj = nn.Linear(embed_dim, 3 * embed_dim // 2, bias=True) self.in_balancer = ActivationBalancer(3 * embed_dim // 2, channel_dim=-1, max_abs=5.0, max_var_per_eig=0.2) self.proj_balancer = ActivationBalancer(embed_dim // 2, channel_dim=-1, max_abs=10.0, min_positive=0.0, max_positive=1.0) self.out_proj = ScaledLinear( embed_dim // 2, embed_dim, bias=True, initial_scale=0.05 ) self.in_proj2 = nn.Linear(embed_dim, embed_dim // 2, bias=False) self.out_proj2 = ScaledLinear(embed_dim // 2, embed_dim, bias=True, initial_scale=0.05) self.attn_scores_proj_in = nn.Parameter(torch.eye(num_heads)) self.attn_scores_proj_out = nn.Parameter(torch.zeros(num_heads, num_heads)) # linear transformation for positional encoding. self.linear_pos = nn.Linear(embed_dim, embed_dim // 2, 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._reset_parameters() def _reset_parameters(self) -> None: nn.init.uniform_(self.pos_bias_u, -0.05, 0.05) nn.init.uniform_(self.pos_bias_v, -0.05, 0.05) def forward( self, x: Tensor, pos_emb: Tensor, attn_scores_in: Optional[Tensor], key_padding_mask: Optional[Tensor] = None, attn_mask: Optional[Tensor] = None, ) -> Tuple[Tensor, Tensor, Tensor]: r""" Args: x: input to be projected to query, key, value 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 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. Shape: - Inputs: - x: :math:`(L, N, E)` where L is the target 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. - attn_scores_in: :math:`(N, L, L, num_heads)` - 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. - Returns: (attn_output, attn_weights, attn_scores) - attn_output: :math:`(S, N, E)` where S is the sequence length, N is the batch size, E is the embedding dimension. - attn_weights: :math:`(N * N, S, S)` where N is the batch size, H is the num-heads and S is the sequence length. - attn_scores: :math:`(N, S, S, H)`, these are the attn weights before softmax. """ x, weights, scores = self.multi_head_attention_forward( self.in_balancer(self.in_proj(x)), pos_emb, None if attn_scores_in is None else torch.matmul(attn_scores_in, self.attn_scores_proj_in), self.embed_dim, self.num_heads, self.in_proj.weight, self.in_proj.bias, self.dropout, self.out_proj.weight, self.out_proj.bias, training=self.training, key_padding_mask=key_padding_mask, attn_mask=attn_mask, ) if attn_scores_in is not None: attn_scores_out = torch.matmul(scores, self.attn_scores_proj_out) attn_scores_out = attn_scores_out + attn_scores_in else: # Here, add self.attn_scores_proj_in in order to make sure it has # a grad. attn_scores_out = torch.matmul(scores, self.attn_scores_proj_out + self.attn_scores_proj_in) return x, weights, attn_scores_out def rel_shift(self, x: Tensor) -> Tensor: """Compute relative positional encoding. Args: x: Input tensor (batch, head, time1, 2*time1-1). time1 means the length of query vector. 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 assert n == 2 * time1 - 1 # 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, time1), (batch_stride, head_stride, time1_stride - n_stride, n_stride), storage_offset=n_stride * (time1 - 1), ) def multi_head_attention_forward( self, x: Tensor, pos_emb: Tensor, attn_scores_in: Optional[Tensor], embed_dim: 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, attn_mask: Optional[Tensor] = None, ) -> 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: 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. 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. 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_weights: :math:`(N * H, S, S)` where N is the batch size, H is the num-heads, S is the sequence length. - attn_scores: :math:`(N, S, S, H)` where N is the batch size, S is the sequence length and H is the num-heads. """ tgt_len, bsz, _ = x.size() head_dim = embed_dim // (num_heads * 2) assert ( head_dim * num_heads == embed_dim // 2 ), "embed_dim must be divisible by num_heads" scaling = float(head_dim) ** -0.5 # self-attention q, k, v = x.chunk(3, dim=-1) 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, tgt_len, tgt_len]: 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, tgt_len, tgt_len, ]: 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: 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) assert pos_emb_bsz in (1, bsz) # actually it is 1 p = self.proj_balancer(self.linear_pos(pos_emb)).view(pos_emb_bsz, -1, num_heads, head_dim) p = p.transpose(1, 2) # (batch, head, 2*time1-1, d_k) 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.transpose(-2, -1) ) # (batch, head, time1, 2*time1-1) matrix_bd = self.rel_shift(matrix_bd) attn_output_weights = ( matrix_ac + matrix_bd ) # (batch, head, time1, time2) attn_scores_out = attn_output_weights.permute(0, 2, 3, 1) # (batch, time1, time2, head) if attn_scores_in is not None: attn_output_weights = attn_output_weights + attn_scores_in.permute(0, 3, 1, 2) attn_output_weights = attn_output_weights.view( bsz * num_heads, tgt_len, -1 ) 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) attn_output_weights = nn.functional.dropout( attn_output_weights, p=dropout_p, training=training ) attn_output = torch.bmm(attn_output_weights, v) 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 // 2) ) attn_output = nn.functional.linear( attn_output, out_proj_weight, out_proj_bias ) return attn_output, attn_output_weights, attn_scores_out def forward2( self, x: Tensor, attn_weights: Tensor, ) -> Tensor: """ Second forward function, where we re-use the attn_weights returned by the first forward function but with different input. Args: x: input, of shape (seq_len, batch_size, embed_dim) attn_weights: attention weights returned by forward(), of shape (batch_size * num_heads, seq_len, seq_len) Returns: output of the same shape as x, i.e. (seq_len, batch_size, embed_dim) """ num_heads = self.num_heads (seq_len, bsz, embed_dim) = x.shape head_dim = embed_dim // (num_heads * 2) # v: (tgt_len, bsz, embed_dim // 2) v = self.in_proj2(x) v = v.contiguous().view(seq_len, bsz * num_heads, head_dim).transpose(0, 1) # now v: (bsz * num_heads, seq_len, head_dim) attn_output = torch.bmm(attn_weights, v) # attn_output: (bsz * num_heads, seq_len, head_dim) attn_output = ( attn_output.transpose(0, 1) .contiguous() .view(seq_len, bsz, embed_dim // 2) ) # returned value is of shape (seq_len, bsz, embed_dim), like x. return self.out_proj2(attn_output) class FeedforwardModule(nn.Module): """Feedforward module in Conformer model. """ def __init__(self, d_model: int, feedforward_dim: int, dropout: float): super(FeedforwardModule, self).__init__() self.in_proj = nn.Linear(d_model, feedforward_dim) self.balancer = ActivationBalancer(feedforward_dim, channel_dim=-1, max_abs=10.0) self.activation = DoubleSwish() self.dropout = nn.Dropout(dropout) self.out_proj = ScaledLinear(feedforward_dim, d_model, initial_scale=0.01) def forward(self, x: Tensor): x = self.in_proj(x) x = self.balancer(x) x = self.activation(x) x = self.dropout(x) x = self.out_proj(x) return x 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). """ def __init__( self, channels: int, kernel_size: int, bias: bool = True ) -> 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.pointwise_conv1 = nn.Conv1d( 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( 2 * channels, channel_dim=1, max_abs=10.0, min_positive=0.05, max_positive=1.0 ) self.depthwise_conv = nn.Conv1d( channels, channels, kernel_size, stride=1, padding=(kernel_size - 1) // 2, groups=channels, bias=bias, ) self.deriv_balancer2 = ActivationBalancer( channels, 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=0.05, ) def forward(self, x: Tensor, src_key_padding_mask: Optional[Tensor] = None, ) -> Tensor: """Compute convolution module. Args: x: Input tensor (#time, batch, channels). src_key_padding_mask: the mask for the src keys per batch (optional): (batch, #time), contains bool in masked positions. Returns: Tensor: Output tensor (#time, 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) if src_key_padding_mask is not None: x.masked_fill_(src_key_padding_mask.unsqueeze(1).expand_as(x), 0.0) # 1D Depthwise Conv x = self.depthwise_conv(x) x = self.deriv_balancer2(x) x = self.activation(x) x = self.pointwise_conv2(x) # (batch, channel, time) return x.permute(2, 0, 1) 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, dropout: float = 0.1, ) -> 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( nn.Conv2d( in_channels=1, out_channels=layer1_channels, kernel_size=3, padding=1, ), ActivationBalancer(layer1_channels, channel_dim=1), DoubleSwish(), nn.Conv2d( in_channels=layer1_channels, out_channels=layer2_channels, kernel_size=3, stride=2, ), ActivationBalancer(layer2_channels, channel_dim=1), DoubleSwish(), nn.Conv2d( in_channels=layer2_channels, out_channels=layer3_channels, kernel_size=3, stride=2, ), ActivationBalancer(layer3_channels, channel_dim=1), DoubleSwish(), ) out_height = (((in_channels - 1) // 2 - 1) // 2) self.out = ScaledLinear(out_height * layer3_channels, out_channels) self.dropout = nn.Dropout(dropout) 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.dropout(x) return x class AttentionCombine(nn.Module): """ This module combines a list of Tensors, all with the same shape, to produce a single output of that same shape which, in training time, is a random combination of all the inputs; but which in test time will be just the last input. All but the last input will have a linear transform before we randomly combine them; these linear transforms will be initialized to the identity transform. The idea is that the list of Tensors will be a list of outputs of multiple conformer layers. This has a similar effect as iterated loss. (See: DEJA-VU: DOUBLE FEATURE PRESENTATION AND ITERATED LOSS IN DEEP TRANSFORMER NETWORKS). """ def __init__( self, num_channels: int, num_inputs: int, random_prob: float = 0.25, single_prob: float = 0.333, ) -> None: """ Args: num_channels: the number of channels num_inputs: The number of tensor inputs, which equals the number of layers' outputs that are fed into this module. E.g. in an 18-layer neural net if we output layers 16, 12, 18, num_inputs would be 3. random_prob: the probability with which we apply a nontrivial mask, in training mode. single_prob: the probability with which we mask to allow just a single module's output (in training) """ super().__init__() self.random_prob = random_prob self.single_prob = single_prob self.weight = torch.nn.Parameter(torch.zeros(num_channels, num_inputs)) self.bias = torch.nn.Parameter(torch.zeros(num_inputs)) assert 0 <= random_prob <= 1, random_prob assert 0 <= single_prob <= 1, single_prob def forward(self, inputs: List[Tensor]) -> Tensor: """Forward function. Args: inputs: A list of Tensor, e.g. from various layers of a transformer. All must be the same shape, of (*, num_channels) Returns: A Tensor of shape (*, num_channels). In test mode this is just the final input. """ num_inputs = self.weight.shape[1] assert len(inputs) == num_inputs # Shape of weights: (*, num_inputs) num_channels = inputs[0].shape[-1] num_frames = inputs[0].numel() // num_channels ndim = inputs[0].ndim # stacked_inputs: (num_frames, num_channels, num_inputs) stacked_inputs = torch.stack(inputs, dim=ndim).reshape( (num_frames, num_channels, num_inputs) ) weights = (stacked_inputs * self.weight).sum(dim=(1,)) + self.bias if random.random() < 0.002: logging.info(f"Average weights are {weights.softmax(dim=1).mean(dim=0)}") if self.training: # random masking.. mask_start = torch.randint(low=1, high=int(num_inputs / self.random_prob), size=(num_frames,), device=weights.device).unsqueeze(1) # mask will have rows like: [ False, False, False, True, True, .. ] arange = torch.arange(num_inputs, device=weights.device).unsqueeze(0).expand( num_frames, num_inputs) mask = arange >= mask_start apply_single_prob = torch.logical_and(torch.rand(size=(num_frames, 1), device=weights.device) < self.single_prob, mask_start < num_inputs) single_prob_mask = torch.logical_and(apply_single_prob, arange < mask_start - 1) mask = torch.logical_or(mask, single_prob_mask) weights = weights.masked_fill(mask, float('-inf')) weights = weights.softmax(dim=1) # (num_frames, num_channels, num_inputs) * (num_frames, num_inputs, 1) -> (num_frames, num_channels, 1), ans = torch.matmul(stacked_inputs, weights.unsqueeze(2)) # ans: (*, num_channels) ans = ans.reshape(*tuple(inputs[0].shape[:-1]), num_channels) if __name__ == "__main__": # for testing only... print("Weights = ", weights.reshape(num_frames, num_inputs)) return ans def _test_random_combine(): print("_test_random_combine()") num_inputs = 3 num_channels = 50 m = AttentionCombine( num_channels=num_channels, num_inputs=num_inputs, random_prob=0.5, single_prob=0.0) x = [torch.ones(3, 4, num_channels) for _ in range(num_inputs)] y = m(x) assert y.shape == x[0].shape assert torch.allclose(y, x[0]) # .. since actually all ones. def _test_conformer_main(): feature_dim = 50 batch_size = 5 seq_len = 20 feature_dim = 50 # Just make sure the forward pass runs. c = Conformer( num_features=feature_dim, d_model=(64,96), encoder_unmasked_dim=64, nhead=(4,4) ) 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), ) f # to remove flake8 warnings c.eval() f = c( torch.randn(batch_size, seq_len, feature_dim), torch.full((batch_size,), seq_len, dtype=torch.int64), ) f # to remove flake8 warnings if __name__ == "__main__": logging.getLogger().setLevel(logging.INFO) torch.set_num_threads(1) torch.set_num_interop_threads(1) _test_random_combine() _test_conformer_main()