def testExpectedLossWithAlpha75AndZeroGamma(self):
# All zeros correspond to 0.5 probability.
prediction_tensor = tf.constant([[[0, 0, 0],
[0, 0, 0],
[0, 0, 0],
[0, 0, 0]],
[[0, 0, 0],
[0, 0, 0],
[0, 0, 0],
[0, 0, 0]]], tf.float32)
target_tensor = tf.constant([[[0, 1, 0],
[1, 0, 0],
[1, 0, 0],
[0, 0, 1]],
[[0, 0, 1],
[0, 1, 0],
[1, 0, 0],
[1, 0, 0]]], tf.float32)
weights = tf.constant([[1, 1, 1, 1],
[1, 1, 1, 1]], tf.float32)
focal_loss_op = losses.SigmoidFocalClassificationLoss(
anchorwise_output=False, alpha=0.75, gamma=0.0)
focal_loss = focal_loss_op(prediction_tensor, target_tensor,
weights=weights)
with self.test_session() as sess:
focal_loss = sess.run(focal_loss)
self.assertAllClose(
(-math.log(.5) * # x-entropy per class per anchor.
((0.75 * # alpha for positives.
8) + # positives from 8 anchors.
(0.25 * # alpha for negatives.
8 * 2))), # negatives from 8 anchors for two classes.
focal_loss)
def testSameAsSigmoidXEntropyWithNoAlphaAndZeroGamma(self):
prediction_tensor = tf.constant([[[-100, 100, -100],
[100, -100, -100],
[100, 0, -100],
[-100, -100, 100]],
[[-100, 0, 100],
[-100, 100, -100],
[100, 100, 100],
[0, 0, -1]]], tf.float32)
target_tensor = tf.constant([[[0, 1, 0],
[1, 0, 0],
[1, 0, 0],
[0, 0, 1]],
[[0, 0, 1],
[0, 1, 0],
[1, 1, 1],
[1, 0, 0]]], tf.float32)
weights = tf.constant([[1, 1, 1, 1],
[1, 1, 1, 0]], tf.float32)
focal_loss_op = losses.SigmoidFocalClassificationLoss(
anchorwise_output=True, alpha=None, gamma=0.0)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss(
anchorwise_output=True)
focal_loss = focal_loss_op(prediction_tensor, target_tensor,
weights=weights)
sigmoid_loss = sigmoid_loss_op(prediction_tensor, target_tensor,
weights=weights)
with self.test_session() as sess:
sigmoid_loss, focal_loss = sess.run([sigmoid_loss, focal_loss])
self.assertAllClose(sigmoid_loss, focal_loss)
def testIgnorePositiveExampleLossViaAlphaMultiplier(self):
prediction_tensor = tf.constant([[[_logit(0.55)],
[_logit(0.52)],
[_logit(0.50)],
[_logit(0.48)],
[_logit(0.45)]]], tf.float32)
target_tensor = tf.constant([[[1],
[1],
[1],
[0],
[0]]], tf.float32)
weights = tf.constant([[1, 1, 1, 1, 1]], tf.float32)
focal_loss_op = losses.SigmoidFocalClassificationLoss(
anchorwise_output=True, gamma=2.0, alpha=0.0)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss(
anchorwise_output=True)
focal_loss = focal_loss_op(prediction_tensor, target_tensor,
weights=weights)
sigmoid_loss = sigmoid_loss_op(prediction_tensor, target_tensor,
weights=weights)
with self.test_session() as sess:
sigmoid_loss, focal_loss = sess.run([sigmoid_loss, focal_loss])
self.assertAllClose(focal_loss[0][:3], [0., 0., 0.])
order_of_ratio = np.power(10,
np.floor(np.log10(sigmoid_loss[0][3:] /
focal_loss[0][3:])))
self.assertAllClose(order_of_ratio, [1., 1.])
def testNonAnchorWiseOutputComparableToSigmoidXEntropy(self):
prediction_tensor = tf.constant([[[_logit(0.55)],
[_logit(0.52)],
[_logit(0.50)],
[_logit(0.48)],
[_logit(0.45)]]], tf.float32)
target_tensor = tf.constant([[[1],
[1],
[1],
[0],
[0]]], tf.float32)
weights = tf.constant([[1, 1, 1, 1, 1]], tf.float32)
focal_loss_op = losses.SigmoidFocalClassificationLoss(
anchorwise_output=False, gamma=2.0, alpha=None)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss(
anchorwise_output=False)
focal_loss = focal_loss_op(prediction_tensor, target_tensor,
weights=weights)
sigmoid_loss = sigmoid_loss_op(prediction_tensor, target_tensor,
weights=weights)
with self.test_session() as sess:
sigmoid_loss, focal_loss = sess.run([sigmoid_loss, focal_loss])
order_of_ratio = np.power(10,
np.floor(np.log10(sigmoid_loss / focal_loss)))
self.assertAlmostEqual(order_of_ratio, 1.)
def testEasyExamplesProduceSmallLossComparedToSigmoidXEntropy(self):
prediction_tensor = tf.constant([[[_logit(0.97)],
[_logit(0.90)],
[_logit(0.73)],
[_logit(0.27)],
[_logit(0.09)],
[_logit(0.03)]]], tf.float32)
target_tensor = tf.constant([[[1],
[1],
[1],
[0],
[0],
[0]]], tf.float32)
weights = tf.constant([[1, 1, 1, 1, 1, 1]], tf.float32)
focal_loss_op = losses.SigmoidFocalClassificationLoss(
anchorwise_output=True, gamma=2.0, alpha=None)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss(
anchorwise_output=True)
focal_loss = focal_loss_op(prediction_tensor, target_tensor,
weights=weights)
sigmoid_loss = sigmoid_loss_op(prediction_tensor, target_tensor,
weights=weights)
with self.test_session() as sess:
sigmoid_loss, focal_loss = sess.run([sigmoid_loss, focal_loss])
order_of_ratio = np.power(10,
np.floor(np.log10(sigmoid_loss / focal_loss)))
self.assertAllClose(order_of_ratio, [[1000, 100, 10, 10, 100, 1000]])
def _build_classification_loss(loss_config):
"""Builds a classification loss based on the loss config.
Args:
loss_config: A losses_pb2.ClassificationLoss object.
Returns:
Loss based on the config.
Raises:
ValueError: On invalid loss_config.
"""
if not isinstance(loss_config, losses_pb2.ClassificationLoss):
raise ValueError(
'loss_config not of type losses_pb2.ClassificationLoss.')
loss_type = loss_config.WhichOneof('classification_loss')
if loss_type == 'weighted_sigmoid':
config = loss_config.weighted_sigmoid
return losses.WeightedSigmoidClassificationLoss(
anchorwise_output=config.anchorwise_output)
if loss_type == 'weighted_sigmoid_focal':
config = loss_config.weighted_sigmoid_focal
alpha = None
if config.HasField('alpha'):
alpha = config.alpha
return losses.SigmoidFocalClassificationLoss(
anchorwise_output=config.anchorwise_output,
gamma=config.gamma,
alpha=alpha)
if loss_type == 'weighted_softmax':
config = loss_config.weighted_softmax
return losses.WeightedSoftmaxClassificationLoss(
anchorwise_output=config.anchorwise_output,
logit_scale=config.logit_scale)
if loss_type == 'bootstrapped_sigmoid':
config = loss_config.bootstrapped_sigmoid
return losses.BootstrappedSigmoidClassificationLoss(
alpha=config.alpha,
bootstrap_type=('hard' if config.hard_bootstrap else 'soft'),
anchorwise_output=config.anchorwise_output)
raise ValueError('Empty loss config.')