def __call__(self, logits, targets, reduce=True):
pos_similarity, neg_similarity, batch_size = self.get_similarities(logits)
targets_local = FloatTensor(batch_size)
targets_local.fill_(1) # 1: pos_similarity should be higher than neg_similarity
return F.margin_ranking_loss(
pos_similarity, neg_similarity, targets_local, self.config.margin
)
def __init__(self, config, weights=None, *args, **kwargs):
"""Args:
config: Config containing `precision_range_lower`, `precision_range_upper`,
`num_classes`, `num_anchors`
"""
nn.Module.__init__(self)
Loss.__init__(self, config)
self.num_classes = self.config.num_classes
self.num_anchors = self.config.num_anchors
self.precision_range = (
self.config.precision_range_lower,
self.config.precision_range_upper,
)
# Create precision anchor values and distance between anchors.
# coresponding to [alpha_t] and [delta_t] in the paper.
# precision_values: 1D `Tensor` of shape [K], where `K = num_anchors`
# delta: Scalar (since we use equal distance between anchors)
self.precision_values, self.delta = loss_utils.range_to_anchors_and_delta(
self.precision_range, self.num_anchors)
# notation is [b_k] in paper, Parameter of shape [C, K]
# where `C = number of classes` `K = num_anchors`
self.biases = nn.Parameter(
FloatTensor(self.config.num_classes,
self.config.num_anchors).zero_())
self.lambdas = nn.Parameter(
FloatTensor(self.config.num_classes,
self.config.num_anchors).data.fill_(1.0))
def __call__(self, logits, targets, reduce=True):
"""
Computes Kullback-Leibler divergence loss for multiclass classification
probability distribution computed by BinaryCrossEntropyLoss loss
"""
hard_targets, soft_targets = targets
# we clamp the probability between (1e-20, 1 - 1e-20) to avoid log(0) problem
# in the calculation of KLDivergence
soft_targets = FloatTensor(soft_targets).exp().clamp(1e-20, 1 - 1e-20)
probs = F.sigmoid(logits).clamp(1e-20, 1 - 1e-20)
probs_neg = probs.neg().add(1).clamp(1e-20, 1 - 1e-20)
soft_targets_neg = soft_targets.neg().add(1).clamp(1e-20, 1 - 1e-20)
if self.weight is not None:
loss = (
F.kl_div(probs.log(), soft_targets, reduction="none") *
self.weight +
F.kl_div(probs_neg.log(), soft_targets_neg, reduction="none") *
self.weight)
if reduce:
loss = loss.mean()
else:
loss = F.kl_div(probs.log(),
soft_targets,
reduction="mean" if reduce else "none") + F.kl_div(
probs_neg.log(),
soft_targets_neg,
reduction="mean" if reduce else "none",
)
return loss
def __init__(self, lstm: nn.LSTM):
"""
Shapes:
initial_state: (lstm_layers, 1, lstm_hidden_dim) each
"""
self.lstm = lstm
initial_state = (
FloatTensor(lstm.num_layers, 1, lstm.hidden_size).fill_(0),
FloatTensor(lstm.num_layers, 1, lstm.hidden_size).fill_(0),
)
# Stack of (state, (embedding, element))
self.stack = [(initial_state, (self._lstm_output(initial_state),
Element("Root")))]
def __call__(self, m_out, targets, reduce=True):
"""
Computes 1-vs-all binary cross entropy loss for multiclass
classification.
"""
# Converts targets to one-hot representation. Dim: [batch, n_classes]
one_hot_targets = (FloatTensor(targets.size(0),
m_out.size(1)).zero_().scatter_(
1,
targets.unsqueeze(1).data, 1))
# This weighting applies uniform class weights.
# examples_per_class = one_hot_target.sum(0).clamp(min=1)
# total_positive = examples_per_class.sum()
# weights = total_positive.unsqueeze(0) / examples_per_class
loss = F.binary_cross_entropy_with_logits(m_out,
one_hot_targets,
reduction="none")
if self.config.reweight_negative:
# This makes sure we have same weights for all negative classes and
# single positive class. Weight is 1 for the correct class and
# 1 / (n - 1) for other ones.
weights = one_hot_targets + (1.0 - one_hot_targets) / max(
1,
one_hot_targets.size(1) - 1.0)
loss = loss * weights
return loss.sum(1).mean() if reduce else loss.sum(1)
def __call__(self, logits, targets, reduce=True):
"""
Computes soft and hard loss for knowledge distillation
"""
hard_targets, _, _ = targets
# hard targets
one_hot_targets = (
FloatTensor(hard_targets.size(0), logits.size(1))
.zero_()
.scatter_(1, hard_targets.unsqueeze(1).data, 1)
)
prob_loss = KLDivergenceBCELoss(self.config, weight=self.weight)
if self.weight is not None:
hard_loss = (
F.binary_cross_entropy_with_logits(
logits, one_hot_targets, reduction="none"
)
* self.weight
)
if reduce:
hard_loss = hard_loss.mean()
else:
hard_loss = F.binary_cross_entropy_with_logits(
logits, one_hot_targets, reduction="mean" if reduce else "none"
)
return self.t * self.t * prob_loss(logits, targets, reduce=reduce) + hard_loss
def range_to_anchors_and_delta(precision_range, num_anchors):
"""Calculates anchor points from precision range.
Args:
precision_range: an interval (a, b), where 0.0 <= a <= b <= 1.0
num_anchors: int, number of equally spaced anchor points.
Returns:
precision_values: A `Tensor` of [num_anchors] equally spaced values
in the interval precision_range.
delta: The spacing between the values in precision_values.
Raises:
ValueError: If precision_range is invalid.
"""
# Validate precision_range.
if len(precision_range) != 2:
raise ValueError("length of precision_range (%d) must be 2" %
len(precision_range))
if not 0 <= precision_range[0] <= precision_range[1] <= 1:
raise ValueError("precision values must follow 0 <= %f <= %f <= 1" %
(precision_range[0], precision_range[1]))
# Sets precision_values uniformly between min_precision and max_precision.
precision_values = numpy.linspace(start=precision_range[0],
stop=precision_range[1],
num=num_anchors + 1)[1:]
delta = (precision_range[1] - precision_range[0]) / num_anchors
return FloatTensor(precision_values), delta
def __call__(self, logits, targets, reduce=True):
"""
Computes Kullback-Leibler divergence loss for multiclass classification
probability distribution computed by CrossEntropyLoss loss
"""
hard_targets, _, soft_targets_logits = targets
soft_targets = F.softmax(FloatTensor(soft_targets_logits) / self.t,
dim=1)
soft_targets = soft_targets.clamp(1e-10, 1 - 1e-10)
log_probs = F.log_softmax(logits / self.t, 1)
if self.weight is not None:
soft_loss = (F.kl_div(log_probs, soft_targets, reduction="none") *
self.weight)
if reduce:
soft_loss = soft_loss.mean()
else:
soft_loss = F.kl_div(log_probs,
soft_targets,
reduction="mean" if reduce else "none")
soft_loss *= self.t**2 # see https://arxiv.org/pdf/1503.02531.pdf
hard_loss = 0.0
if self.hard_weight > 0.0:
hard_loss = F.cross_entropy(
logits,
hard_targets,
reduction="mean" if reduce else "none",
weight=self.weight,
)
return (1.0 -
self.hard_weight) * soft_loss + self.hard_weight * hard_loss
def _prepare_labels_weights(logits, targets, weights=None):
"""
Args:
logits: Variable :math:`(N, C)` where `C = number of classes`
targets: Variable :math:`(N)` where each value is
`0 <= targets[i] <= C-1`
weights: Coefficients for the loss. Must be a `Tensor` of shape
[N] or [N, C], where `N = batch_size`, `C = number of classes`.
Returns:
labels: Tensor of shape [N, C], one-hot representation
weights: Tensor of shape broadcastable to labels
"""
N, C = logits.size()
# Converts targets to one-hot representation. Dim: [N, C]
labels = FloatTensor(N, C).zero_().scatter(1,
targets.unsqueeze(1).data,
1)
if weights is None:
weights = FloatTensor(N).data.fill_(1.0)
if weights.dim() == 1:
weights.unsqueeze_(-1)
return labels, weights
def __call__(self, logits, targets, reduce=True):
"""
Computes Kullback-Leibler divergence loss for multiclass classification
probability distribution computed by CrossEntropyLoss loss
"""
hard_targets, soft_targets = targets
soft_targets = FloatTensor(soft_targets).exp().clamp(1e-20, 1 - 1e-20)
log_probs = F.log_softmax(logits, 1)
if self.weight is not None:
loss = F.kl_div(log_probs, soft_targets,
reduction="none") * self.weight
if reduce:
loss = loss.mean()
else:
loss = F.kl_div(log_probs,
soft_targets,
reduction="mean" if reduce else "none")
return loss
def from_config(cls, config: Config, metadata: FieldMeta):
label_weights = getattr(metadata, "label_weights", None)
if label_weights is not None:
label_weights = FloatTensor(label_weights)
return cls(metadata.vocab.itos,
create_loss(config.loss, weight=label_weights), config)
