def ssd_losses(logits,
localisations,
gclasses,
glocalisations,
gscores,
match_threshold=0.5,
negative_ratio=3.,
alpha=1.,
label_smoothing=0.,
scope=None):
"""Loss functions for training the SSD 300 VGG network.
This function defines the different loss components of the SSD, and
adds them to the TF loss collection.
Arguments:
logits: (list of) predictions logits Tensors;
localisations: (list of) localisations Tensors;
gclasses: (list of) groundtruth labels Tensors;
glocalisations: (list of) groundtruth localisations Tensors;
gscores: (list of) groundtruth score Tensors;
"""
with tf.name_scope(scope, 'ssd_losses'):
l_cross_pos = []
l_cross_neg = []
l_loc = []
for i in range(len(logits)):
dtype = logits[i].dtype
with tf.name_scope('block_%i' % i):
# Determine weights Tensor.
pmask = gscores[i] > match_threshold
fpmask = tf.cast(pmask, dtype)
n_positives = tf.reduce_sum(fpmask)
# Select some random negative entries.
# n_entries = np.prod(gclasses[i].get_shape().as_list())
# r_positive = n_positives / n_entries
# r_negative = negative_ratio * n_positives / (n_entries - n_positives)
# Negative mask.
no_classes = tf.cast(pmask, tf.int32)
predictions = slim.softmax(logits[i])
nmask = tf.logical_and(tf.logical_not(pmask),
gscores[i] > -0.5)
fnmask = tf.cast(nmask, dtype)
nvalues = tf.where(nmask, predictions[:, :, :, :, 0],
1. - fnmask)
nvalues_flat = tf.reshape(nvalues, [-1])
# Number of negative entries to select.
n_neg = tf.cast(negative_ratio * n_positives, tf.int32)
n_neg = tf.maximum(n_neg, tf.size(nvalues_flat) // 8)
n_neg = tf.maximum(n_neg, tf.shape(nvalues)[0] * 4)
max_neg_entries = 1 + tf.cast(tf.reduce_sum(fnmask), tf.int32)
n_neg = tf.minimum(n_neg, max_neg_entries)
val, idxes = tf.nn.top_k(-nvalues_flat, k=n_neg)
minval = val[-1]
# Final negative mask.
nmask = tf.logical_and(nmask, -nvalues > minval)
fnmask = tf.cast(nmask, dtype)
# Add cross-entropy loss.
with tf.name_scope('cross_entropy_pos'):
loss = tf.nn.sparse_softmax_cross_entropy_with_logits(
logits=logits[i], labels=gclasses[i])
loss = tf.losses.compute_weighted_loss(loss, fpmask)
l_cross_pos.append(loss)
with tf.name_scope('cross_entropy_neg'):
loss = tf.nn.sparse_softmax_cross_entropy_with_logits(
logits=logits[i], labels=no_classes)
loss = tf.losses.compute_weighted_loss(loss, fnmask)
l_cross_neg.append(loss)
# Add localization loss: smooth L1, L2, ...
with tf.name_scope('localization'):
# Weights Tensor: positive mask + random negative.
weights = tf.expand_dims(alpha * fpmask, axis=-1)
loss = custom_layers.abs_smooth(localisations[i] -
glocalisations[i])
loss = tf.losses.compute_weighted_loss(loss, weights)
l_loc.append(loss)
# Additional total losses...
with tf.name_scope('total'):
total_cross_pos = tf.add_n(l_cross_pos, 'cross_entropy_pos')
total_cross_neg = tf.add_n(l_cross_neg, 'cross_entropy_neg')
total_cross = tf.add(total_cross_pos, total_cross_neg,
'cross_entropy')
total_loc = tf.add_n(l_loc, 'localization')
# Add to EXTRA LOSSES TF.collection
tf.add_to_collection('EXTRA_LOSSES', total_cross_pos)
tf.add_to_collection('EXTRA_LOSSES', total_cross_neg)
tf.add_to_collection('EXTRA_LOSSES', total_cross)
tf.add_to_collection('EXTRA_LOSSES', total_loc)
def ssd_losses(logits,
localisations,
gclasses,
glocalisations,
gscores,
match_threshold=0.5,
negative_ratio=3.,
alpha=1.,
label_smoothing=0.,
device='/cpu:0',
scope=None):
with tf.name_scope(scope, 'ssd_losses'):
lshape = tfe.get_shape(logits[0], 5)
num_classes = lshape[-1]
batch_size = lshape[0]
# Flatten out all vectors!
flogits = []
fgclasses = []
fgscores = []
flocalisations = []
fglocalisations = []
for i in range(len(logits)):
flogits.append(tf.reshape(logits[i], [-1, num_classes]))
fgclasses.append(tf.reshape(gclasses[i], [-1]))
fgscores.append(tf.reshape(gscores[i], [-1]))
flocalisations.append(tf.reshape(localisations[i], [-1, 4]))
fglocalisations.append(tf.reshape(glocalisations[i], [-1, 4]))
# And concat the crap!
logits = tf.concat(flogits, axis=0)
gclasses = tf.concat(fgclasses, axis=0)
gscores = tf.concat(fgscores, axis=0)
localisations = tf.concat(flocalisations, axis=0)
glocalisations = tf.concat(fglocalisations, axis=0)
dtype = logits.dtype
# Compute positive matching mask...
pmask = gscores > match_threshold
fpmask = tf.cast(pmask, dtype)
n_positives = tf.reduce_sum(fpmask)
# Hard negative mining...
no_classes = tf.cast(pmask, tf.int32)
predictions = slim.softmax(logits)
nmask = tf.logical_and(tf.logical_not(pmask), gscores > -0.5)
fnmask = tf.cast(nmask, dtype)
nvalues = tf.where(nmask, predictions[:, 0], 1. - fnmask)
nvalues_flat = tf.reshape(nvalues, [-1])
# Number of negative entries to select.
max_neg_entries = tf.cast(tf.reduce_sum(fnmask), tf.int32)
n_neg = tf.cast(negative_ratio * n_positives, tf.int32) + batch_size
n_neg = tf.minimum(n_neg, max_neg_entries)
val, idxes = tf.nn.top_k(-nvalues_flat, k=n_neg)
max_hard_pred = -val[-1]
# Final negative mask.
nmask = tf.logical_and(nmask, nvalues < max_hard_pred)
fnmask = tf.cast(nmask, dtype)
# Add cross-entropy loss.
with tf.name_scope('cross_entropy_pos'):
loss = tf.nn.sparse_softmax_cross_entropy_with_logits(
logits=logits, labels=gclasses)
loss = tf.div(tf.reduce_sum(loss * fpmask),
batch_size,
name='value')
tf.losses.add_loss(loss)
with tf.name_scope('cross_entropy_neg'):
loss = tf.nn.sparse_softmax_cross_entropy_with_logits(
logits=logits, labels=no_classes)
loss = tf.div(tf.reduce_sum(loss * fnmask),
batch_size,
name='value')
tf.losses.add_loss(loss)
# Add localization loss: smooth L1, L2, ...
with tf.name_scope('localization'):
# Weights Tensor: positive mask + random negative.
weights = tf.expand_dims(alpha * fpmask, axis=-1)
loss = custom_layers.abs_smooth(localisations - glocalisations)
loss = tf.div(tf.reduce_sum(loss * weights),
batch_size,
name='value')
tf.losses.add_loss(loss)