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|
## @package attention
# Module caffe2.python.attention
from caffe2.python import brew
class AttentionType:
Regular, Recurrent, Dot, SoftCoverage = tuple(range(4))
def s(scope, name):
# We have to manually scope due to our internal/external blob
# relationships.
return "{}/{}".format(str(scope), str(name))
# c_i = \sum_j w_{ij}\textbf{s}_j
def _calc_weighted_context(
model,
encoder_outputs_transposed,
encoder_output_dim,
attention_weights_3d,
scope,
):
# [batch_size, encoder_output_dim, 1]
attention_weighted_encoder_context = brew.batch_mat_mul(
model,
[encoder_outputs_transposed, attention_weights_3d],
s(scope, 'attention_weighted_encoder_context'),
)
# [batch_size, encoder_output_dim]
attention_weighted_encoder_context, _ = model.net.Reshape(
attention_weighted_encoder_context,
[
attention_weighted_encoder_context,
s(scope, 'attention_weighted_encoder_context_old_shape'),
],
shape=[1, -1, encoder_output_dim],
)
return attention_weighted_encoder_context
# Calculate a softmax over the passed in attention energy logits
def _calc_attention_weights(
model,
attention_logits_transposed,
scope,
encoder_lengths=None,
):
if encoder_lengths is not None:
attention_logits_transposed = model.net.SequenceMask(
[attention_logits_transposed, encoder_lengths],
['masked_attention_logits'],
mode='sequence',
)
# [batch_size, encoder_length, 1]
attention_weights_3d = brew.softmax(
model,
attention_logits_transposed,
s(scope, 'attention_weights_3d'),
engine='CUDNN',
axis=1,
)
return attention_weights_3d
# e_{ij} = \textbf{v}^T tanh \alpha(\textbf{h}_{i-1}, \textbf{s}_j)
def _calc_attention_logits_from_sum_match(
model,
decoder_hidden_encoder_outputs_sum,
encoder_output_dim,
scope,
):
# [encoder_length, batch_size, encoder_output_dim]
decoder_hidden_encoder_outputs_sum = model.net.Tanh(
decoder_hidden_encoder_outputs_sum,
decoder_hidden_encoder_outputs_sum,
)
# [encoder_length, batch_size, 1]
attention_logits = brew.fc(
model,
decoder_hidden_encoder_outputs_sum,
s(scope, 'attention_logits'),
dim_in=encoder_output_dim,
dim_out=1,
axis=2,
freeze_bias=True,
)
# [batch_size, encoder_length, 1]
attention_logits_transposed = brew.transpose(
model,
attention_logits,
s(scope, 'attention_logits_transposed'),
axes=[1, 0, 2],
)
return attention_logits_transposed
# \textbf{W}^\alpha used in the context of \alpha_{sum}(a,b)
def _apply_fc_weight_for_sum_match(
model,
input,
dim_in,
dim_out,
scope,
name,
):
output = brew.fc(
model,
input,
s(scope, name),
dim_in=dim_in,
dim_out=dim_out,
axis=2,
)
output = model.net.Squeeze(
output,
output,
dims=[0],
)
return output
# Implement RecAtt due to section 4.1 in http://arxiv.org/abs/1601.03317
def apply_recurrent_attention(
model,
encoder_output_dim,
encoder_outputs_transposed,
weighted_encoder_outputs,
decoder_hidden_state_t,
decoder_hidden_state_dim,
attention_weighted_encoder_context_t_prev,
scope,
encoder_lengths=None,
):
weighted_prev_attention_context = _apply_fc_weight_for_sum_match(
model=model,
input=attention_weighted_encoder_context_t_prev,
dim_in=encoder_output_dim,
dim_out=encoder_output_dim,
scope=scope,
name='weighted_prev_attention_context',
)
weighted_decoder_hidden_state = _apply_fc_weight_for_sum_match(
model=model,
input=decoder_hidden_state_t,
dim_in=decoder_hidden_state_dim,
dim_out=encoder_output_dim,
scope=scope,
name='weighted_decoder_hidden_state',
)
# [1, batch_size, encoder_output_dim]
decoder_hidden_encoder_outputs_sum_tmp = model.net.Add(
[
weighted_prev_attention_context,
weighted_decoder_hidden_state,
],
s(scope, 'decoder_hidden_encoder_outputs_sum_tmp'),
)
# [encoder_length, batch_size, encoder_output_dim]
decoder_hidden_encoder_outputs_sum = model.net.Add(
[
weighted_encoder_outputs,
decoder_hidden_encoder_outputs_sum_tmp,
],
s(scope, 'decoder_hidden_encoder_outputs_sum'),
broadcast=1,
)
attention_logits_transposed = _calc_attention_logits_from_sum_match(
model=model,
decoder_hidden_encoder_outputs_sum=decoder_hidden_encoder_outputs_sum,
encoder_output_dim=encoder_output_dim,
scope=scope,
)
# [batch_size, encoder_length, 1]
attention_weights_3d = _calc_attention_weights(
model=model,
attention_logits_transposed=attention_logits_transposed,
scope=scope,
encoder_lengths=encoder_lengths,
)
# [batch_size, encoder_output_dim, 1]
attention_weighted_encoder_context = _calc_weighted_context(
model=model,
encoder_outputs_transposed=encoder_outputs_transposed,
encoder_output_dim=encoder_output_dim,
attention_weights_3d=attention_weights_3d,
scope=scope,
)
return attention_weighted_encoder_context, attention_weights_3d, [
decoder_hidden_encoder_outputs_sum,
]
def apply_regular_attention(
model,
encoder_output_dim,
encoder_outputs_transposed,
weighted_encoder_outputs,
decoder_hidden_state_t,
decoder_hidden_state_dim,
scope,
encoder_lengths=None,
):
weighted_decoder_hidden_state = _apply_fc_weight_for_sum_match(
model=model,
input=decoder_hidden_state_t,
dim_in=decoder_hidden_state_dim,
dim_out=encoder_output_dim,
scope=scope,
name='weighted_decoder_hidden_state',
)
# [encoder_length, batch_size, encoder_output_dim]
decoder_hidden_encoder_outputs_sum = model.net.Add(
[weighted_encoder_outputs, weighted_decoder_hidden_state],
s(scope, 'decoder_hidden_encoder_outputs_sum'),
broadcast=1,
use_grad_hack=1,
)
attention_logits_transposed = _calc_attention_logits_from_sum_match(
model=model,
decoder_hidden_encoder_outputs_sum=decoder_hidden_encoder_outputs_sum,
encoder_output_dim=encoder_output_dim,
scope=scope,
)
# [batch_size, encoder_length, 1]
attention_weights_3d = _calc_attention_weights(
model=model,
attention_logits_transposed=attention_logits_transposed,
scope=scope,
encoder_lengths=encoder_lengths,
)
# [batch_size, encoder_output_dim, 1]
attention_weighted_encoder_context = _calc_weighted_context(
model=model,
encoder_outputs_transposed=encoder_outputs_transposed,
encoder_output_dim=encoder_output_dim,
attention_weights_3d=attention_weights_3d,
scope=scope,
)
return attention_weighted_encoder_context, attention_weights_3d, [
decoder_hidden_encoder_outputs_sum,
]
def apply_dot_attention(
model,
encoder_output_dim,
# [batch_size, encoder_output_dim, encoder_length]
encoder_outputs_transposed,
# [1, batch_size, decoder_state_dim]
decoder_hidden_state_t,
decoder_hidden_state_dim,
scope,
encoder_lengths=None,
):
if decoder_hidden_state_dim != encoder_output_dim:
weighted_decoder_hidden_state = brew.fc(
model,
decoder_hidden_state_t,
s(scope, 'weighted_decoder_hidden_state'),
dim_in=decoder_hidden_state_dim,
dim_out=encoder_output_dim,
axis=2,
)
else:
weighted_decoder_hidden_state = decoder_hidden_state_t
# [batch_size, decoder_state_dim]
squeezed_weighted_decoder_hidden_state = model.net.Squeeze(
weighted_decoder_hidden_state,
s(scope, 'squeezed_weighted_decoder_hidden_state'),
dims=[0],
)
# [batch_size, decoder_state_dim, 1]
expanddims_squeezed_weighted_decoder_hidden_state = model.net.ExpandDims(
squeezed_weighted_decoder_hidden_state,
squeezed_weighted_decoder_hidden_state,
dims=[2],
)
# [batch_size, encoder_output_dim, 1]
attention_logits_transposed = model.net.BatchMatMul(
[
encoder_outputs_transposed,
expanddims_squeezed_weighted_decoder_hidden_state,
],
s(scope, 'attention_logits'),
trans_a=1,
)
# [batch_size, encoder_length, 1]
attention_weights_3d = _calc_attention_weights(
model=model,
attention_logits_transposed=attention_logits_transposed,
scope=scope,
encoder_lengths=encoder_lengths,
)
# [batch_size, encoder_output_dim, 1]
attention_weighted_encoder_context = _calc_weighted_context(
model=model,
encoder_outputs_transposed=encoder_outputs_transposed,
encoder_output_dim=encoder_output_dim,
attention_weights_3d=attention_weights_3d,
scope=scope,
)
return attention_weighted_encoder_context, attention_weights_3d, []
def apply_soft_coverage_attention(
model,
encoder_output_dim,
encoder_outputs_transposed,
weighted_encoder_outputs,
decoder_hidden_state_t,
decoder_hidden_state_dim,
scope,
encoder_lengths,
coverage_t_prev,
coverage_weights,
):
weighted_decoder_hidden_state = _apply_fc_weight_for_sum_match(
model=model,
input=decoder_hidden_state_t,
dim_in=decoder_hidden_state_dim,
dim_out=encoder_output_dim,
scope=scope,
name='weighted_decoder_hidden_state',
)
# [encoder_length, batch_size, encoder_output_dim]
decoder_hidden_encoder_outputs_sum_tmp = model.net.Add(
[weighted_encoder_outputs, weighted_decoder_hidden_state],
s(scope, 'decoder_hidden_encoder_outputs_sum_tmp'),
broadcast=1,
)
# [batch_size, encoder_length]
coverage_t_prev_2d = model.net.Squeeze(
coverage_t_prev,
s(scope, 'coverage_t_prev_2d'),
dims=[0],
)
# [encoder_length, batch_size]
coverage_t_prev_transposed = brew.transpose(
model,
coverage_t_prev_2d,
s(scope, 'coverage_t_prev_transposed'),
)
# [encoder_length, batch_size, encoder_output_dim]
scaled_coverage_weights = model.net.Mul(
[coverage_weights, coverage_t_prev_transposed],
s(scope, 'scaled_coverage_weights'),
broadcast=1,
axis=0,
)
# [encoder_length, batch_size, encoder_output_dim]
decoder_hidden_encoder_outputs_sum = model.net.Add(
[decoder_hidden_encoder_outputs_sum_tmp, scaled_coverage_weights],
s(scope, 'decoder_hidden_encoder_outputs_sum'),
)
# [batch_size, encoder_length, 1]
attention_logits_transposed = _calc_attention_logits_from_sum_match(
model=model,
decoder_hidden_encoder_outputs_sum=decoder_hidden_encoder_outputs_sum,
encoder_output_dim=encoder_output_dim,
scope=scope,
)
# [batch_size, encoder_length, 1]
attention_weights_3d = _calc_attention_weights(
model=model,
attention_logits_transposed=attention_logits_transposed,
scope=scope,
encoder_lengths=encoder_lengths,
)
# [batch_size, encoder_output_dim, 1]
attention_weighted_encoder_context = _calc_weighted_context(
model=model,
encoder_outputs_transposed=encoder_outputs_transposed,
encoder_output_dim=encoder_output_dim,
attention_weights_3d=attention_weights_3d,
scope=scope,
)
# [batch_size, encoder_length]
attention_weights_2d = model.net.Squeeze(
attention_weights_3d,
s(scope, 'attention_weights_2d'),
dims=[2],
)
coverage_t = model.net.Add(
[coverage_t_prev, attention_weights_2d],
s(scope, 'coverage_t'),
broadcast=1,
)
return (
attention_weighted_encoder_context,
attention_weights_3d,
[decoder_hidden_encoder_outputs_sum],
coverage_t,
)
|
