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(alpha=0.75,
gamma=0.0)
focal_loss = tf.reduce_sum(
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 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(gamma=2.0,
alpha=0.0)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss()
focal_loss = tf.reduce_sum(focal_loss_op(prediction_tensor,
target_tensor,
weights=weights),
axis=2)
sigmoid_loss = tf.reduce_sum(sigmoid_loss_op(prediction_tensor,
target_tensor,
weights=weights),
axis=2)
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 testEasyExamplesProduceSmallLossComparedToSigmoidXEntropy(self):
prediction_tensor = tf.constant(
[[[_logit(0.97)], [_logit(0.91)], [_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(gamma=2.0,
alpha=None)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss()
focal_loss = tf.reduce_sum(focal_loss_op(prediction_tensor,
target_tensor,
weights=weights),
axis=2)
sigmoid_loss = tf.reduce_sum(sigmoid_loss_op(prediction_tensor,
target_tensor,
weights=weights),
axis=2)
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':
return losses.WeightedSigmoidClassificationLoss()
if loss_type == 'weighted_sigmoid_focal':
config = loss_config.weighted_sigmoid_focal
alpha = None
if config.HasField('alpha'):
alpha = config.alpha
return losses.SigmoidFocalClassificationLoss(gamma=config.gamma,
alpha=alpha)
if loss_type == 'weighted_softmax':
config = loss_config.weighted_softmax
return losses.WeightedSoftmaxClassificationLoss(
logit_scale=config.logit_scale)
if loss_type == 'weighted_logits_softmax':
config = loss_config.weighted_logits_softmax
return losses.WeightedSoftmaxClassificationAgainstLogitsLoss(
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'))
raise ValueError('Empty loss config.')
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(gamma=2.0,
alpha=None)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss()
focal_loss = tf.reduce_sum(
focal_loss_op(prediction_tensor, target_tensor, weights=weights))
sigmoid_loss = tf.reduce_sum(
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 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(alpha=None,
gamma=0.0)
sigmoid_loss_op = losses.WeightedSigmoidClassificationLoss()
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)