def build(self, input_shape):
if self._add_pos_embed:
self._pos_embed = AddPositionEmbs(
posemb_init=tf.keras.initializers.RandomNormal(stddev=0.02),
name='posembed_input')
self._dropout = layers.Dropout(rate=self._dropout_rate)
self._encoder_layers = []
# Set layer norm epsilons to 1e-6 to be consistent with JAX implementation.
# https://flax.readthedocs.io/en/latest/_autosummary/flax.deprecated.nn.LayerNorm.html
for i in range(self._num_layers):
encoder_layer = nn_blocks.TransformerEncoderBlock(
inner_activation=activations.gelu,
num_attention_heads=self._num_heads,
inner_dim=self._mlp_dim,
output_dropout=self._dropout_rate,
attention_dropout=self._attention_dropout_rate,
kernel_regularizer=self._kernel_regularizer,
kernel_initializer=self._kernel_initializer,
norm_first=True,
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 1, self._num_layers),
norm_epsilon=1e-6)
self._encoder_layers.append(encoder_layer)
self._norm = layers.LayerNormalization(epsilon=1e-6)
super().build(input_shape)
def _build_scale_permuted_network(self,
net,
input_width,
weighted_fusion=False):
"""Builds scale-permuted network."""
net_sizes = [int(math.ceil(input_width / 2**2))] * len(net)
net_block_fns = [self._init_block_fn] * len(net)
num_outgoing_connections = [0] * len(net)
endpoints = {}
for i, block_spec in enumerate(self._block_specs):
# Find out specs for the target block.
target_width = int(math.ceil(input_width / 2**block_spec.level))
target_num_filters = int(FILTER_SIZE_MAP[block_spec.level] *
self._filter_size_scale)
target_block_fn = block_spec.block_fn
# Resample then merge input0 and input1.
parents = []
input0 = block_spec.input_offsets[0]
input1 = block_spec.input_offsets[1]
x0 = self._resample_with_alpha(
inputs=net[input0],
input_width=net_sizes[input0],
input_block_fn=net_block_fns[input0],
target_width=target_width,
target_num_filters=target_num_filters,
target_block_fn=target_block_fn,
alpha=self._resample_alpha)
parents.append(x0)
num_outgoing_connections[input0] += 1
x1 = self._resample_with_alpha(
inputs=net[input1],
input_width=net_sizes[input1],
input_block_fn=net_block_fns[input1],
target_width=target_width,
target_num_filters=target_num_filters,
target_block_fn=target_block_fn,
alpha=self._resample_alpha)
parents.append(x1)
num_outgoing_connections[input1] += 1
# Merge 0 outdegree blocks to the output block.
if block_spec.is_output:
for j, (j_feat, j_connections) in enumerate(
zip(net, num_outgoing_connections)):
if j_connections == 0 and (j_feat.shape[2] == target_width
and j_feat.shape[3]
== x0.shape[3]):
parents.append(j_feat)
num_outgoing_connections[j] += 1
# pylint: disable=g-direct-tensorflow-import
if weighted_fusion:
dtype = parents[0].dtype
parent_weights = [
tf.nn.relu(
tf.cast(tf.Variable(1.0,
name='block{}_fusion{}'.format(
i, j)),
dtype=dtype)) for j in range(len(parents))
]
weights_sum = tf.add_n(parent_weights)
parents = [
parents[i] * parent_weights[i] / (weights_sum + 0.0001)
for i in range(len(parents))
]
# Fuse all parent nodes then build a new block.
x = tf_utils.get_activation(self._activation_fn)(tf.add_n(parents))
x = self._block_group(
inputs=x,
filters=target_num_filters,
strides=1,
block_fn_cand=target_block_fn,
block_repeats=self._block_repeats,
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 1,
len(self._block_specs)),
name='scale_permuted_block_{}'.format(i + 1))
net.append(x)
net_sizes.append(target_width)
net_block_fns.append(target_block_fn)
num_outgoing_connections.append(0)
# Save output feats.
if block_spec.is_output:
if block_spec.level in endpoints:
raise ValueError(
'Duplicate feats found for output level {}.'.format(
block_spec.level))
if (block_spec.level < self._min_level
or block_spec.level > self._max_level):
logging.warning(
'SpineNet output level out of range [min_level, max_level] = '
'[%s, %s] will not be used for further processing.',
self._min_level, self._max_level)
endpoints[str(block_spec.level)] = x
return endpoints
def __init__(
self,
model_id: int,
temporal_strides: List[int],
temporal_kernel_sizes: List[Tuple[int]],
use_self_gating: List[int] = None,
input_specs=layers.InputSpec(shape=[None, None, None, None, 3]),
stem_type='v0',
stem_conv_temporal_kernel_size=5,
stem_conv_temporal_stride=2,
stem_pool_temporal_stride=2,
init_stochastic_depth_rate=0.0,
activation='relu',
se_ratio=None,
use_sync_bn=False,
norm_momentum=0.99,
norm_epsilon=0.001,
kernel_initializer='VarianceScaling',
kernel_regularizer=None,
bias_regularizer=None,
**kwargs):
"""Initializes a 3D ResNet model.
Args:
model_id: An `int` of depth of ResNet backbone model.
temporal_strides: A list of integers that specifies the temporal strides
for all 3d blocks.
temporal_kernel_sizes: A list of tuples that specifies the temporal kernel
sizes for all 3d blocks in different block groups.
use_self_gating: A list of booleans to specify applying self-gating module
or not in each block group. If None, self-gating is not applied.
input_specs: A `tf.keras.layers.InputSpec` of the input tensor.
stem_type: A `str` of stem type of ResNet. Default to `v0`. If set to
`v1`, use ResNet-D type stem (https://arxiv.org/abs/1812.01187).
stem_conv_temporal_kernel_size: An `int` of temporal kernel size for the
first conv layer.
stem_conv_temporal_stride: An `int` of temporal stride for the first conv
layer.
stem_pool_temporal_stride: An `int` of temporal stride for the first pool
layer.
init_stochastic_depth_rate: A `float` of initial stochastic depth rate.
activation: A `str` of name of the activation function.
se_ratio: A `float` or None. Ratio of the Squeeze-and-Excitation layer.
use_sync_bn: If True, use synchronized batch normalization.
norm_momentum: A `float` of normalization momentum for the moving average.
norm_epsilon: A `float` added to variance to avoid dividing by zero.
kernel_initializer: A str for kernel initializer of convolutional layers.
kernel_regularizer: A `tf.keras.regularizers.Regularizer` object for
Conv2D. Default to None.
bias_regularizer: A `tf.keras.regularizers.Regularizer` object for Conv2D.
Default to None.
**kwargs: Additional keyword arguments to be passed.
"""
self._model_id = model_id
self._temporal_strides = temporal_strides
self._temporal_kernel_sizes = temporal_kernel_sizes
self._input_specs = input_specs
self._stem_type = stem_type
self._stem_conv_temporal_kernel_size = stem_conv_temporal_kernel_size
self._stem_conv_temporal_stride = stem_conv_temporal_stride
self._stem_pool_temporal_stride = stem_pool_temporal_stride
self._use_self_gating = use_self_gating
self._se_ratio = se_ratio
self._init_stochastic_depth_rate = init_stochastic_depth_rate
self._use_sync_bn = use_sync_bn
self._activation = activation
self._norm_momentum = norm_momentum
self._norm_epsilon = norm_epsilon
if use_sync_bn:
self._norm = layers.experimental.SyncBatchNormalization
else:
self._norm = layers.BatchNormalization
self._kernel_initializer = kernel_initializer
self._kernel_regularizer = kernel_regularizer
self._bias_regularizer = bias_regularizer
if tf.keras.backend.image_data_format() == 'channels_last':
bn_axis = -1
else:
bn_axis = 1
# Build ResNet3D backbone.
inputs = tf.keras.Input(shape=input_specs.shape[1:])
# Build stem.
if stem_type == 'v0':
x = layers.Conv3D(
filters=64,
kernel_size=[stem_conv_temporal_kernel_size, 7, 7],
strides=[stem_conv_temporal_stride, 2, 2],
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(inputs)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
elif stem_type == 'v1':
x = layers.Conv3D(
filters=32,
kernel_size=[stem_conv_temporal_kernel_size, 3, 3],
strides=[stem_conv_temporal_stride, 2, 2],
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(inputs)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
x = layers.Conv3D(filters=32,
kernel_size=[1, 3, 3],
strides=[1, 1, 1],
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(x)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
x = layers.Conv3D(filters=64,
kernel_size=[1, 3, 3],
strides=[1, 1, 1],
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(x)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
else:
raise ValueError(f'Stem type {stem_type} not supported.')
temporal_kernel_size = 1 if stem_pool_temporal_stride == 1 else 3
x = layers.MaxPool3D(pool_size=[temporal_kernel_size, 3, 3],
strides=[stem_pool_temporal_stride, 2, 2],
padding='same')(x)
# Build intermediate blocks and endpoints.
resnet_specs = RESNET_SPECS[model_id]
if len(temporal_strides) != len(resnet_specs) or len(
temporal_kernel_sizes) != len(resnet_specs):
raise ValueError(
'Number of blocks in temporal specs should equal to resnet_specs.'
)
endpoints = {}
for i, resnet_spec in enumerate(resnet_specs):
if resnet_spec[0] == 'bottleneck3d':
block_fn = nn_blocks_3d.BottleneckBlock3D
else:
raise ValueError('Block fn `{}` is not supported.'.format(
resnet_spec[0]))
x = self._block_group(
inputs=x,
filters=resnet_spec[1],
temporal_kernel_sizes=temporal_kernel_sizes[i],
temporal_strides=temporal_strides[i],
spatial_strides=(1 if i == 0 else 2),
block_fn=block_fn,
block_repeats=resnet_spec[2],
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 2, 5),
use_self_gating=use_self_gating[i]
if use_self_gating else False,
name='block_group_l{}'.format(i + 2))
endpoints[str(i + 2)] = x
self._output_specs = {l: endpoints[l].get_shape() for l in endpoints}
super(ResNet3D, self).__init__(inputs=inputs,
outputs=endpoints,
**kwargs)
def __init__(self,
model_id,
input_specs=layers.InputSpec(shape=[None, None, None, 3]),
depth_multiplier=1.0,
stem_type='v0',
se_ratio=None,
init_stochastic_depth_rate=0.0,
activation='relu',
use_sync_bn=False,
norm_momentum=0.99,
norm_epsilon=0.001,
kernel_initializer='VarianceScaling',
kernel_regularizer=None,
bias_regularizer=None,
**kwargs):
"""ResNet initialization function.
Args:
model_id: `int` depth of ResNet backbone model.
input_specs: `tf.keras.layers.InputSpec` specs of the input tensor.
depth_multiplier: `float` a depth multiplier to uniformaly scale up all
layers in channel size in ResNet.
stem_type: `str` stem type of ResNet. Default to `v0`. If set to `v1`,
use ResNet-C type stem (https://arxiv.org/abs/1812.01187).
se_ratio: `float` or None. Ratio of the Squeeze-and-Excitation layer.
init_stochastic_depth_rate: `float` initial stochastic depth rate.
activation: `str` name of the activation function.
use_sync_bn: if True, use synchronized batch normalization.
norm_momentum: `float` normalization omentum for the moving average.
norm_epsilon: `float` small float added to variance to avoid dividing by
zero.
kernel_initializer: kernel_initializer for convolutional layers.
kernel_regularizer: tf.keras.regularizers.Regularizer object for Conv2D.
Default to None.
bias_regularizer: tf.keras.regularizers.Regularizer object for Conv2d.
Default to None.
**kwargs: keyword arguments to be passed.
"""
self._model_id = model_id
self._input_specs = input_specs
self._depth_multiplier = depth_multiplier
self._stem_type = stem_type
self._se_ratio = se_ratio
self._init_stochastic_depth_rate = init_stochastic_depth_rate
self._use_sync_bn = use_sync_bn
self._activation = activation
self._norm_momentum = norm_momentum
self._norm_epsilon = norm_epsilon
if use_sync_bn:
self._norm = layers.experimental.SyncBatchNormalization
else:
self._norm = layers.BatchNormalization
self._kernel_initializer = kernel_initializer
self._kernel_regularizer = kernel_regularizer
self._bias_regularizer = bias_regularizer
if tf.keras.backend.image_data_format() == 'channels_last':
bn_axis = -1
else:
bn_axis = 1
# Build ResNet.
inputs = tf.keras.Input(shape=input_specs.shape[1:])
if stem_type == 'v0':
x = layers.Conv2D(filters=int(64 * self._depth_multiplier),
kernel_size=7,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(inputs)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
elif stem_type == 'v1':
x = layers.Conv2D(filters=int(32 * self._depth_multiplier),
kernel_size=3,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(inputs)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
x = layers.Conv2D(filters=int(32 * self._depth_multiplier),
kernel_size=3,
strides=1,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(x)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
x = layers.Conv2D(filters=int(64 * self._depth_multiplier),
kernel_size=3,
strides=1,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(x)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
else:
raise ValueError('Stem type {} not supported.'.format(stem_type))
x = layers.MaxPool2D(pool_size=3, strides=2, padding='same')(x)
endpoints = {}
for i, spec in enumerate(RESNET_SPECS[model_id]):
if spec[0] == 'residual':
block_fn = nn_blocks.ResidualBlock
elif spec[0] == 'bottleneck':
block_fn = nn_blocks.BottleneckBlock
else:
raise ValueError('Block fn `{}` is not supported.'.format(
spec[0]))
x = self._block_group(
inputs=x,
filters=int(spec[1] * self._depth_multiplier),
strides=(1 if i == 0 else 2),
block_fn=block_fn,
block_repeats=spec[2],
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 2, 5),
name='block_group_l{}'.format(i + 2))
endpoints[str(i + 2)] = x
self._output_specs = {l: endpoints[l].get_shape() for l in endpoints}
super(ResNet, self).__init__(inputs=inputs,
outputs=endpoints,
**kwargs)
def __init__(self,
model_id,
output_stride,
input_specs=layers.InputSpec(shape=[None, None, None, 3]),
stem_type='v0',
se_ratio=None,
init_stochastic_depth_rate=0.0,
multigrid=None,
last_stage_repeats=1,
activation='relu',
use_sync_bn=False,
norm_momentum=0.99,
norm_epsilon=0.001,
kernel_initializer='VarianceScaling',
kernel_regularizer=None,
bias_regularizer=None,
**kwargs):
"""Initializes a ResNet model with DeepLab modification.
Args:
<<<<<<< HEAD
model_id: `int` depth of ResNet backbone model.
output_stride: `int` output stride, ratio of input to output resolution.
input_specs: `tf.keras.layers.InputSpec` specs of the input tensor.
stem_type: `standard` or `deeplab`, deeplab replaces 7x7 conv by 3 3x3
convs.
se_ratio: `float` or None. Ratio of the Squeeze-and-Excitation layer.
init_stochastic_depth_rate: `float` initial stochastic depth rate.
multigrid: `Tuple` of the same length as the number of blocks in the last
resnet stage.
last_stage_repeats: `int`, how many times last stage is repeated.
activation: `str` name of the activation function.
use_sync_bn: if True, use synchronized batch normalization.
norm_momentum: `float` normalization omentum for the moving average.
norm_epsilon: `float` small float added to variance to avoid dividing by
zero.
kernel_initializer: kernel_initializer for convolutional layers.
kernel_regularizer: tf.keras.regularizers.Regularizer object for Conv2D.
Default to None.
bias_regularizer: tf.keras.regularizers.Regularizer object for Conv2d.
Default to None.
**kwargs: keyword arguments to be passed.
=======
model_id: An `int` specifies depth of ResNet backbone model.
output_stride: An `int` of output stride, ratio of input to output
resolution.
input_specs: A `tf.keras.layers.InputSpec` of the input tensor.
stem_type: A `str` of stem type. Can be `standard` or `deeplab`. `deeplab`
replaces 7x7 conv by 3 3x3 convs.
se_ratio: A `float` or None. Ratio of the Squeeze-and-Excitation layer.
init_stochastic_depth_rate: A `float` of initial stochastic depth rate.
multigrid: A tuple of the same length as the number of blocks in the last
resnet stage.
last_stage_repeats: An `int` that specifies how many times last stage is
repeated.
activation: A `str` name of the activation function.
use_sync_bn: If True, use synchronized batch normalization.
norm_momentum: A `float` of normalization momentum for the moving average.
norm_epsilon: A `float` added to variance to avoid dividing by zero.
kernel_initializer: A str for kernel initializer of convolutional layers.
kernel_regularizer: A `tf.keras.regularizers.Regularizer` object for
Conv2D. Default to None.
bias_regularizer: A `tf.keras.regularizers.Regularizer` object for Conv2D.
Default to None.
**kwargs: Additional keyword arguments to be passed.
>>>>>>> upstream/master
"""
self._model_id = model_id
self._output_stride = output_stride
self._input_specs = input_specs
self._use_sync_bn = use_sync_bn
self._activation = activation
self._norm_momentum = norm_momentum
self._norm_epsilon = norm_epsilon
if use_sync_bn:
self._norm = layers.experimental.SyncBatchNormalization
else:
self._norm = layers.BatchNormalization
self._kernel_initializer = kernel_initializer
self._kernel_regularizer = kernel_regularizer
self._bias_regularizer = bias_regularizer
self._stem_type = stem_type
self._se_ratio = se_ratio
self._init_stochastic_depth_rate = init_stochastic_depth_rate
if tf.keras.backend.image_data_format() == 'channels_last':
bn_axis = -1
else:
bn_axis = 1
# Build ResNet.
inputs = tf.keras.Input(shape=input_specs.shape[1:])
if stem_type == 'v0':
x = layers.Conv2D(filters=64,
kernel_size=7,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(inputs)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
elif stem_type == 'v1':
x = layers.Conv2D(filters=64,
kernel_size=3,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(inputs)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
x = layers.Conv2D(filters=64,
kernel_size=3,
strides=1,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(x)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
x = layers.Conv2D(filters=128,
kernel_size=3,
strides=1,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(x)
x = self._norm(axis=bn_axis,
momentum=norm_momentum,
epsilon=norm_epsilon)(x)
x = tf_utils.get_activation(activation)(x)
else:
raise ValueError('Stem type {} not supported.'.format(stem_type))
x = layers.MaxPool2D(pool_size=3, strides=2, padding='same')(x)
normal_resnet_stage = int(np.math.log2(self._output_stride)) - 2
endpoints = {}
for i in range(normal_resnet_stage + 1):
spec = RESNET_SPECS[model_id][i]
if spec[0] == 'bottleneck':
block_fn = nn_blocks.BottleneckBlock
else:
raise ValueError('Block fn `{}` is not supported.'.format(
spec[0]))
x = self._block_group(
inputs=x,
filters=spec[1],
strides=(1 if i == 0 else 2),
dilation_rate=1,
block_fn=block_fn,
block_repeats=spec[2],
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 2,
4 + last_stage_repeats),
name='block_group_l{}'.format(i + 2))
endpoints[str(i + 2)] = x
dilation_rate = 2
for i in range(normal_resnet_stage + 1, 3 + last_stage_repeats):
spec = RESNET_SPECS[model_id][i] if i < 3 else RESNET_SPECS[
model_id][-1]
if spec[0] == 'bottleneck':
block_fn = nn_blocks.BottleneckBlock
else:
raise ValueError('Block fn `{}` is not supported.'.format(
spec[0]))
x = self._block_group(
inputs=x,
filters=spec[1],
strides=1,
dilation_rate=dilation_rate,
block_fn=block_fn,
block_repeats=spec[2],
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 2,
4 + last_stage_repeats),
multigrid=multigrid if i >= 3 else None,
name='block_group_l{}'.format(i + 2))
dilation_rate *= 2
endpoints[str(normal_resnet_stage + 2)] = x
self._output_specs = {l: endpoints[l].get_shape() for l in endpoints}
super(DilatedResNet, self).__init__(inputs=inputs,
outputs=endpoints,
**kwargs)
def __init__(
self,
model_id: int,
input_specs: tf.keras.layers.InputSpec = layers.InputSpec(
shape=[None, None, None, 3]),
depth_multiplier: float = 1.0,
stem_type: str = 'v0',
resnetd_shortcut: bool = False,
replace_stem_max_pool: bool = False,
se_ratio: Optional[float] = None,
init_stochastic_depth_rate: float = 0.0,
activation: str = 'relu',
use_sync_bn: bool = False,
norm_momentum: float = 0.99,
norm_epsilon: float = 0.001,
kernel_initializer: str = 'VarianceScaling',
kernel_regularizer: Optional[tf.keras.regularizers.Regularizer] = None,
bias_regularizer: Optional[tf.keras.regularizers.Regularizer] = None,
**kwargs):
"""Initializes a ResNet model.
Args:
model_id: An `int` of the depth of ResNet backbone model.
input_specs: A `tf.keras.layers.InputSpec` of the input tensor.
depth_multiplier: A `float` of the depth multiplier to uniformaly scale up
all layers in channel size. This argument is also referred to as
`width_multiplier` in (https://arxiv.org/abs/2103.07579).
stem_type: A `str` of stem type of ResNet. Default to `v0`. If set to
`v1`, use ResNet-D type stem (https://arxiv.org/abs/1812.01187).
resnetd_shortcut: A `bool` of whether to use ResNet-D shortcut in
downsampling blocks.
replace_stem_max_pool: A `bool` of whether to replace the max pool in stem
with a stride-2 conv,
se_ratio: A `float` or None. Ratio of the Squeeze-and-Excitation layer.
init_stochastic_depth_rate: A `float` of initial stochastic depth rate.
activation: A `str` name of the activation function.
use_sync_bn: If True, use synchronized batch normalization.
norm_momentum: A `float` of normalization momentum for the moving average.
norm_epsilon: A small `float` added to variance to avoid dividing by zero.
kernel_initializer: A str for kernel initializer of convolutional layers.
kernel_regularizer: A `tf.keras.regularizers.Regularizer` object for
Conv2D. Default to None.
bias_regularizer: A `tf.keras.regularizers.Regularizer` object for Conv2D.
Default to None.
**kwargs: Additional keyword arguments to be passed.
"""
self._model_id = model_id
self._input_specs = input_specs
self._depth_multiplier = depth_multiplier
self._stem_type = stem_type
self._resnetd_shortcut = resnetd_shortcut
self._replace_stem_max_pool = replace_stem_max_pool
self._se_ratio = se_ratio
self._init_stochastic_depth_rate = init_stochastic_depth_rate
self._use_sync_bn = use_sync_bn
self._activation = activation
self._norm_momentum = norm_momentum
self._norm_epsilon = norm_epsilon
if use_sync_bn:
self._norm = layers.experimental.SyncBatchNormalization
else:
self._norm = layers.BatchNormalization
self._kernel_initializer = kernel_initializer
self._kernel_regularizer = kernel_regularizer
self._bias_regularizer = bias_regularizer
if tf.keras.backend.image_data_format() == 'channels_last':
bn_axis = -1
else:
bn_axis = 1
# Build ResNet.
inputs = tf.keras.Input(shape=input_specs.shape[1:])
if stem_type == 'v0':
x = layers.Conv2D(
filters=int(64 * self._depth_multiplier),
kernel_size=7,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(
inputs)
x = self._norm(
axis=bn_axis, momentum=norm_momentum, epsilon=norm_epsilon)(
x)
x = tf_utils.get_activation(activation, use_keras_layer=True)(x)
elif stem_type == 'v1':
x = layers.Conv2D(
filters=int(32 * self._depth_multiplier),
kernel_size=3,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(
inputs)
x = self._norm(
axis=bn_axis, momentum=norm_momentum, epsilon=norm_epsilon)(
x)
x = tf_utils.get_activation(activation, use_keras_layer=True)(x)
x = layers.Conv2D(
filters=int(32 * self._depth_multiplier),
kernel_size=3,
strides=1,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(
x)
x = self._norm(
axis=bn_axis, momentum=norm_momentum, epsilon=norm_epsilon)(
x)
x = tf_utils.get_activation(activation, use_keras_layer=True)(x)
x = layers.Conv2D(
filters=int(64 * self._depth_multiplier),
kernel_size=3,
strides=1,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(
x)
x = self._norm(
axis=bn_axis, momentum=norm_momentum, epsilon=norm_epsilon)(
x)
x = tf_utils.get_activation(activation, use_keras_layer=True)(x)
else:
raise ValueError('Stem type {} not supported.'.format(stem_type))
if replace_stem_max_pool:
x = layers.Conv2D(
filters=int(64 * self._depth_multiplier),
kernel_size=3,
strides=2,
use_bias=False,
padding='same',
kernel_initializer=self._kernel_initializer,
kernel_regularizer=self._kernel_regularizer,
bias_regularizer=self._bias_regularizer)(
x)
x = self._norm(
axis=bn_axis, momentum=norm_momentum, epsilon=norm_epsilon)(
x)
x = tf_utils.get_activation(activation, use_keras_layer=True)(x)
else:
x = layers.MaxPool2D(pool_size=3, strides=2, padding='same')(x)
endpoints = {}
for i, spec in enumerate(RESNET_SPECS[model_id]):
if spec[0] == 'residual':
block_fn = nn_blocks.ResidualBlock
elif spec[0] == 'bottleneck':
block_fn = nn_blocks.BottleneckBlock
else:
raise ValueError('Block fn `{}` is not supported.'.format(spec[0]))
x = self._block_group(
inputs=x,
filters=int(spec[1] * self._depth_multiplier),
strides=(1 if i == 0 else 2),
block_fn=block_fn,
block_repeats=spec[2],
stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
self._init_stochastic_depth_rate, i + 2, 5),
name='block_group_l{}'.format(i + 2))
endpoints[str(i + 2)] = x
self._output_specs = {l: endpoints[l].get_shape() for l in endpoints}
super(ResNet, self).__init__(inputs=inputs, outputs=endpoints, **kwargs)
