def __init__(self,
reduction=tf.losses.Reduction.AUTO,
name=None,
lambda_weight=None,
temperature=1.0,
ragged=False):
"""ListMLE loss.
Args:
reduction: (Optional) The `tf.keras.losses.Reduction` to use (see
`tf.keras.losses.Loss`).
name: (Optional) The name for the op.
lambda_weight: (Optional) A lambdaweight to apply to the loss. Can be one
of `tfr.keras.losses.DCGLambdaWeight`,
`tfr.keras.losses.NDCGLambdaWeight`,
`tfr.keras.losses.PrecisionLambdaWeight`, or,
`tfr.keras.losses.ListMLELambdaWeight`.
temperature: (Optional) The temperature to use for scaling the logits.
ragged: (Optional) If True, this loss will accept ragged tensors. If
False, this loss will accept dense tensors.
"""
super().__init__(reduction, name, lambda_weight, temperature, ragged)
self._loss = losses_impl.ListMLELoss(
name='{}_impl'.format(name) if name else None,
lambda_weight=lambda_weight,
temperature=temperature,
ragged=ragged)
def __init__(self,
reduction=tf.losses.Reduction.AUTO,
name=None,
lambda_weight=None):
super(ListMLELoss, self).__init__(reduction, name)
self._loss = losses_impl.ListMLELoss(name='{}_impl'.format(name),
lambda_weight=lambda_weight)
def test_list_mle_loss_tie(self):
with tf.Graph().as_default():
tf.compat.v1.set_random_seed(1)
scores = [[0., ln(2), ln(3)]]
labels = [[0., 0., 1.]]
reduction = tf.compat.v1.losses.Reduction.SUM_BY_NONZERO_WEIGHTS
with self.cached_session():
loss_fn = losses_impl.ListMLELoss(name=None)
self.assertAlmostEqual(
loss_fn.compute(labels, scores, None, reduction).eval(),
-((ln(3. / (3 + 2 + 1)) + ln(2. / (2 + 1)) + ln(1. / 1))),
places=5)
def test_list_mle_loss_lambda_weight(self):
with tf.Graph().as_default():
scores = [[0., ln(3), ln(2)], [0., ln(2), ln(3)]]
labels = [[0., 2., 1.], [1., 0., 2.]]
lw = losses_impl.ListMLELambdaWeight(
rank_discount_fn=lambda rank: tf.pow(2., 3 - rank) - 1.)
reduction = tf.compat.v1.losses.Reduction.SUM_BY_NONZERO_WEIGHTS
with self.cached_session():
loss_fn = losses_impl.ListMLELoss(name=None, lambda_weight=lw)
self.assertAlmostEqual(
loss_fn.compute(labels, scores, None, reduction).eval(),
-((3 * ln(3. / (3 + 2 + 1)) + 1 * ln(2. / (2 + 1)) +
0 * ln(1. / 1)) +
(3 * ln(3. /
(3 + 2 + 1)) + 1 * ln(1. /
(1 + 2)) + 0 * ln(2. / 2)))
/ 2,
places=5)
def _list_mle_loss(
labels,
logits,
weights=None,
lambda_weight=None,
reduction=tf.compat.v1.losses.Reduction.SUM_BY_NONZERO_WEIGHTS,
name=None):
"""Computes the ListMLE loss [Xia et al.
2008] for a list.
Given the labels of graded relevance l_i and the logits s_i, we calculate
the ListMLE loss for the given list.
The `lambda_weight` re-weights examples based on l_i and r_i.
The recommended weighting scheme is the formulation presented in the
"Position-Aware ListMLE" paper (Lan et al.) and available using
create_p_list_mle_lambda_weight() factory function above.
Args:
labels: A `Tensor` of the same shape as `logits` representing graded
relevance.
logits: A `Tensor` with shape [batch_size, list_size]. Each value is the
ranking score of the corresponding item.
weights: A scalar, a `Tensor` with shape [batch_size, 1] for list-wise
weights, or a `Tensor` with shape [batch_size, list_size] for item-wise
weights.
lambda_weight: A `DCGLambdaWeight` instance.
reduction: One of `tf.losses.Reduction` except `NONE`. Describes how to
reduce training loss over batch.
name: A string used as the name for this loss.
Returns:
An op for the ListMLE loss.
"""
loss = losses_impl.ListMLELoss(name, lambda_weight)
with tf.compat.v1.name_scope(loss.name, 'list_mle_loss',
(labels, logits, weights)):
return loss.compute(labels, logits, weights, reduction)
def test_list_mle_loss(self):
with tf.Graph().as_default():
scores = [[0., ln(3), ln(2)], [0., ln(2), ln(3)]]
labels = [[0., 2., 1.], [1., 0., 2.]]
weights = [[2.], [1.]]
reduction = tf.compat.v1.losses.Reduction.SUM_BY_NONZERO_WEIGHTS
with self.cached_session():
loss_fn = losses_impl.ListMLELoss(name=None)
self.assertAlmostEqual(
loss_fn.compute(labels, scores, None, reduction).eval(),
-((ln(3. / (3 + 2 + 1)) + ln(2. / (2 + 1)) + ln(1. / 1)) +
(ln(3. / (3 + 2 + 1)) + ln(1. /
(1 + 2)) + ln(2. / 2))) / 2,
places=5)
self.assertAlmostEqual(
loss_fn.compute(labels, scores, weights, reduction).eval(),
-(2 * (ln(3. /
(3 + 2 + 1)) + ln(2. /
(2 + 1)) + ln(1. / 1)) + 1 *
(ln(3. / (3 + 2 + 1)) + ln(1. /
(1 + 2)) + ln(2. / 2))) / 2,
places=5)
def make_loss_metric_fn(loss_key,
weights_feature_name=None,
lambda_weight=None,
name=None):
"""Factory method to create a metric based on a loss.
Args:
loss_key: A key in `RankingLossKey`.
weights_feature_name: A `string` specifying the name of the weights feature
in `features` dict.
lambda_weight: A `_LambdaWeight` object.
name: A `string` used as the name for this metric.
Returns:
A metric fn with the following Args:
* `labels`: A `Tensor` of the same shape as `predictions` representing
graded relevance.
* `predictions`: A `Tensor` with shape [batch_size, list_size]. Each value
is the ranking score of the corresponding example.
* `features`: A dict of `Tensor`s that contains all features.
"""
metric_dict = {
RankingLossKey.PAIRWISE_HINGE_LOSS:
losses_impl.PairwiseHingeLoss(name, lambda_weight=lambda_weight),
RankingLossKey.PAIRWISE_LOGISTIC_LOSS:
losses_impl.PairwiseLogisticLoss(name, lambda_weight=lambda_weight),
RankingLossKey.PAIRWISE_SOFT_ZERO_ONE_LOSS:
losses_impl.PairwiseSoftZeroOneLoss(
name, lambda_weight=lambda_weight),
RankingLossKey.SOFTMAX_LOSS:
losses_impl.SoftmaxLoss(name, lambda_weight=lambda_weight),
RankingLossKey.SIGMOID_CROSS_ENTROPY_LOSS:
losses_impl.SigmoidCrossEntropyLoss(name),
RankingLossKey.MEAN_SQUARED_LOSS:
losses_impl.MeanSquaredLoss(name),
RankingLossKey.LIST_MLE_LOSS:
losses_impl.ListMLELoss(name, lambda_weight=lambda_weight),
RankingLossKey.APPROX_NDCG_LOSS:
losses_impl.ApproxNDCGLoss(name),
RankingLossKey.APPROX_MRR_LOSS:
losses_impl.ApproxMRRLoss(name),
RankingLossKey.GUMBEL_APPROX_NDCG_LOSS: losses_impl.ApproxNDCGLoss(name),
}
def _get_weights(features):
"""Get weights tensor from features and reshape it to 2-D if necessary."""
weights = None
if weights_feature_name:
weights = tf.convert_to_tensor(value=features[weights_feature_name])
# Convert weights to a 2-D Tensor.
weights = utils.reshape_to_2d(weights)
return weights
def metric_fn(labels, predictions, features):
"""Defines the metric fn."""
weights = _get_weights(features)
loss = metric_dict.get(loss_key, None)
if loss is None:
raise ValueError('loss_key {} not supported.'.format(loss_key))
return loss.eval_metric(labels, predictions, weights)
return metric_fn