File size: 6,830 Bytes
a257816 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 |
import torch
def subsequent_mask(
size: int,
device: torch.device = torch.device("cpu"),
) -> torch.Tensor:
"""Create mask for subsequent steps (size, size).
This mask is used only in decoder which works in an auto-regressive mode.
This means the current step could only do attention with its left steps.
In encoder, fully attention is used when streaming is not necessary and
the sequence is not long. In this case, no attention mask is needed.
When streaming is need, chunk-based attention is used in encoder. See
subsequent_chunk_mask for the chunk-based attention mask.
Args:
size (int): size of mask
str device (str): "cpu" or "cuda" or torch.Tensor.device
dtype (torch.device): result dtype
Returns:
torch.Tensor: mask
Examples:
>>> subsequent_mask(3)
[[1, 0, 0],
[1, 1, 0],
[1, 1, 1]]
"""
arange = torch.arange(size, device=device)
mask = arange.expand(size, size)
arange = arange.unsqueeze(-1)
mask = mask <= arange
return mask
def subsequent_chunk_mask(
size: int,
chunk_size: int,
num_left_chunks: int = -1,
device: torch.device = torch.device("cpu"),
) -> torch.Tensor:
"""Create mask for subsequent steps (size, size) with chunk size,
this is for streaming encoder
Args:
size (int): size of mask
chunk_size (int): size of chunk
num_left_chunks (int): number of left chunks
<0: use full chunk
>=0: use num_left_chunks
device (torch.device): "cpu" or "cuda" or torch.Tensor.device
Returns:
torch.Tensor: mask
Examples:
>>> subsequent_chunk_mask(4, 2)
[[1, 1, 0, 0],
[1, 1, 0, 0],
[1, 1, 1, 1],
[1, 1, 1, 1]]
"""
ret = torch.zeros(size, size, device=device, dtype=torch.bool)
for i in range(size):
if num_left_chunks < 0:
start = 0
else:
start = max((i // chunk_size - num_left_chunks) * chunk_size, 0)
ending = min((i // chunk_size + 1) * chunk_size, size)
ret[i, start:ending] = True
return ret
def add_optional_chunk_mask(xs: torch.Tensor,
masks: torch.Tensor,
use_dynamic_chunk: bool,
use_dynamic_left_chunk: bool,
decoding_chunk_size: int,
static_chunk_size: int,
num_decoding_left_chunks: int,
enable_full_context: bool = True):
""" Apply optional mask for encoder.
Args:
xs (torch.Tensor): padded input, (B, L, D), L for max length
mask (torch.Tensor): mask for xs, (B, 1, L)
use_dynamic_chunk (bool): whether to use dynamic chunk or not
use_dynamic_left_chunk (bool): whether to use dynamic left chunk for
training.
decoding_chunk_size (int): decoding chunk size for dynamic chunk, it's
0: default for training, use random dynamic chunk.
<0: for decoding, use full chunk.
>0: for decoding, use fixed chunk size as set.
static_chunk_size (int): chunk size for static chunk training/decoding
if it's greater than 0, if use_dynamic_chunk is true,
this parameter will be ignored
num_decoding_left_chunks: number of left chunks, this is for decoding,
the chunk size is decoding_chunk_size.
>=0: use num_decoding_left_chunks
<0: use all left chunks
enable_full_context (bool):
True: chunk size is either [1, 25] or full context(max_len)
False: chunk size ~ U[1, 25]
Returns:
torch.Tensor: chunk mask of the input xs.
"""
# Whether to use chunk mask or not
if use_dynamic_chunk:
max_len = xs.size(1)
if decoding_chunk_size < 0:
chunk_size = max_len
num_left_chunks = -1
elif decoding_chunk_size > 0:
chunk_size = decoding_chunk_size
num_left_chunks = num_decoding_left_chunks
else:
# chunk size is either [1, 25] or full context(max_len).
# Since we use 4 times subsampling and allow up to 1s(100 frames)
# delay, the maximum frame is 100 / 4 = 25.
chunk_size = torch.randint(1, max_len, (1, )).item()
num_left_chunks = -1
if chunk_size > max_len // 2 and enable_full_context:
chunk_size = max_len
else:
chunk_size = chunk_size % 25 + 1
if use_dynamic_left_chunk:
max_left_chunks = (max_len - 1) // chunk_size
num_left_chunks = torch.randint(0, max_left_chunks,
(1, )).item()
chunk_masks = subsequent_chunk_mask(xs.size(1), chunk_size,
num_left_chunks,
xs.device) # (L, L)
chunk_masks = chunk_masks.unsqueeze(0) # (1, L, L)
chunk_masks = masks & chunk_masks # (B, L, L)
elif static_chunk_size > 0:
num_left_chunks = num_decoding_left_chunks
chunk_masks = subsequent_chunk_mask(xs.size(1), static_chunk_size,
num_left_chunks,
xs.device) # (L, L)
chunk_masks = chunk_masks.unsqueeze(0) # (1, L, L)
chunk_masks = masks & chunk_masks # (B, L, L)
else:
chunk_masks = masks
return chunk_masks
def make_pad_mask(lengths: torch.Tensor, max_len: int = 0) -> torch.Tensor:
"""Make mask tensor containing indices of padded part.
See description of make_non_pad_mask.
Args:
lengths (torch.Tensor): Batch of lengths (B,).
Returns:
torch.Tensor: Mask tensor containing indices of padded part.
Examples:
>>> lengths = [5, 3, 2]
>>> make_pad_mask(lengths)
masks = [[0, 0, 0, 0 ,0],
[0, 0, 0, 1, 1],
[0, 0, 1, 1, 1]]
"""
batch_size = lengths.size(0)
max_len = max_len if max_len > 0 else lengths.max().item()
seq_range = torch.arange(0,
max_len,
dtype=torch.int64,
device=lengths.device)
seq_range_expand = seq_range.unsqueeze(0).expand(batch_size, max_len)
seq_length_expand = lengths.unsqueeze(-1)
mask = seq_range_expand >= seq_length_expand
return mask
|