def optimize_loss(loss,
global_step,
learning_rate,
optimizer,
gradient_noise_scale=None,
gradient_multipliers=None,
clip_gradients=None,
learning_rate_decay_fn=None,
update_ops=None,
variables=None,
name=None,
summaries=None,
colocate_gradients_with_ops=False,
increment_global_step=True):
"""Given loss and parameters for optimizer, returns a training op.
Various ways of passing optimizers, include:
- string, name of the optimizer like 'SGD', 'Adam', see OPTIMIZER_CLS_NAMES
for full list. E.g. `optimize_loss(..., optimizer='Adam')`.
- function, takes learning rate `Tensor` as argument and must return
`Optimizer` instance. E.g. `optimize_loss(...,
optimizer=lambda lr: tf.train.MomentumOptimizer(lr, momentum=0.5))`.
Alternatively, if `learning_rate` is `None`, the function takes no
arguments. E.g. `optimize_loss(..., learning_rate=None,
optimizer=lambda: tf.train.MomentumOptimizer(0.5, momentum=0.5))`.
- class, subclass of `Optimizer` that takes only one required argument -
learning rate, such as AdamOptimizer, AdagradOptimizer.
E.g. `optimize_loss(..., optimizer=tf.train.AdagradOptimizer)`.
- object, instance of subclass of `Optimizer`.
E.g., `optimizer_loss(..., optimizer=tf.train.AdagradOptimizer(0.5))`.
Args:
loss: Scalar `Tensor`.
global_step: Scalar int `Tensor`, step counter to update on each step
unless `increment_global_step` is `False`. If not supplied,
it will be fetched from the default graph (see
`tf.train.get_global_step` for details). If it's
not been created, no step will be incremented with each weight
update. `learning_rate_decay_fn` requires `global_step`.
learning_rate: float or `Tensor`, magnitude of update per each training
step. Can be `None`.
optimizer: string, class or optimizer instance, used as trainer.
string should be name of optimizer, like 'SGD',
'Adam', 'Adagrad'. Full list in OPTIMIZER_CLS_NAMES constant.
class should be sub-class of `tf.Optimizer` that implements
`compute_gradients` and `apply_gradients` functions.
optimizer instance should be instantiation of `tf.Optimizer`
sub-class and have `compute_gradients` and `apply_gradients`
functions.
gradient_noise_scale: float or None, adds 0-mean normal noise scaled by this
value.
gradient_multipliers: dict of variables or variable names to floats.
If present, gradients for specified
variables will be multiplied by given constant.
clip_gradients: float, callable or `None`. If float, is provided, a global
clipping is applied to prevent the norm of the gradient to exceed this
value. Alternatively, a callable can be provided e.g.: adaptive_clipping.
This callable takes a `list` of `(gradients, variables)` `tuple`s and
returns the same thing with the gradients modified.
learning_rate_decay_fn: function, takes `learning_rate` and `global_step`
`Tensor`s, returns `Tensor`.
Can be used to implement any learning rate decay
functions.
For example: `tf.train.exponential_decay`.
Ignored if `learning_rate` is not supplied.
update_ops: list of update `Operation`s to execute at each step. If `None`,
uses elements of UPDATE_OPS collection. The order of execution
between `update_ops` and `loss` is non-deterministic.
variables: list of variables to optimize or
`None` to use all trainable variables.
name: The name for this operation is used to scope operations and summaries.
summaries: List of internal quantities to visualize on tensorboard. If not
set only the loss and the learning rate will be reported. The
complete list is in OPTIMIZER_SUMMARIES.
colocate_gradients_with_ops: If True, try colocating gradients with the
corresponding op.
increment_global_step: Whether to increment `global_step`. If your model
calls `optimize_loss` multiple times per training step (e.g. to optimize
different parts of the model), use this arg to avoid incrementing
`global_step` more times than necessary.
Returns:
Training op.
Raises:
ValueError: if:
* `loss` is an invalid type or shape.
* `global_step` is an invalid type or shape.
* `learning_rate` is an invalid type or value.
* `optimizer` is wrong type.
* `clip_gradients` is not float or callable.
* `learning_rate` and `learning_rate_decay_fn` are supplied, but no
`global_step` is available.
* `gradients` is empty
"""
loss = ops.convert_to_tensor(loss)
contrib_framework.assert_scalar(loss)
if global_step is None:
global_step = contrib_framework.get_global_step()
else:
contrib_framework.assert_global_step(global_step)
with vs.variable_scope(name, "OptimizeLoss", [loss, global_step]):
# Update ops take UPDATE_OPS collection if not provided.
if update_ops is None:
update_ops = set(ops.get_collection(ops.GraphKeys.UPDATE_OPS))
# Make sure update ops are ran before computing loss.
if update_ops:
loss = control_flow_ops.with_dependencies(list(update_ops), loss)
# Learning rate variable, with possible decay.
lr = None
if learning_rate is not None:
if (isinstance(learning_rate, ops.Tensor) and
learning_rate.get_shape().ndims == 0):
lr = learning_rate
elif isinstance(learning_rate, float):
if learning_rate < 0.0:
raise ValueError("Invalid learning_rate %s.", learning_rate)
lr = vs.get_variable(
"learning_rate", [],
trainable=False,
initializer=init_ops.constant_initializer(learning_rate))
else:
raise ValueError("Learning rate should be 0d Tensor or float. "
"Got %s of type %s" % (str(learning_rate),
str(type(learning_rate))))
if summaries is None:
summaries = ["loss", "learning_rate"]
else:
for summ in summaries:
if summ not in OPTIMIZER_SUMMARIES:
raise ValueError("Summaries should be one of [%s], you provided %s." %
(", ".join(OPTIMIZER_SUMMARIES), summ))
if learning_rate is not None and learning_rate_decay_fn is not None:
if global_step is None:
raise ValueError("global_step is required for learning_rate_decay_fn.")
lr = learning_rate_decay_fn(lr, global_step)
if "learning_rate" in summaries:
summary.scalar("learning_rate", lr)
# Create optimizer, given specified parameters.
if isinstance(optimizer, six.string_types):
if lr is None:
raise ValueError("Learning rate is None, but should be specified if "
"optimizer is string (%s)." % optimizer)
if optimizer not in OPTIMIZER_CLS_NAMES:
raise ValueError(
"Optimizer name should be one of [%s], you provided %s." %
(", ".join(OPTIMIZER_CLS_NAMES), optimizer))
opt = OPTIMIZER_CLS_NAMES[optimizer](learning_rate=lr)
elif (isinstance(optimizer, type) and
issubclass(optimizer, optimizer_.Optimizer)):
if lr is None:
raise ValueError("Learning rate is None, but should be specified if "
"optimizer is class (%s)." % optimizer)
opt = optimizer(learning_rate=lr)
elif isinstance(optimizer, optimizer_.Optimizer):
opt = optimizer
elif callable(optimizer):
if learning_rate is not None:
opt = optimizer(lr)
else:
opt = optimizer()
if not isinstance(opt, optimizer_.Optimizer):
raise ValueError("Unrecognized optimizer: function should return "
"subclass of Optimizer. Got %s." % str(opt))
else:
raise ValueError("Unrecognized optimizer: should be string, "
"subclass of Optimizer, instance of "
"subclass of Optimizer or function with one argument. "
"Got %s." % str(optimizer))
# All trainable variables, if specific variables are not specified.
if variables is None:
variables = vars_.trainable_variables()
# Compute gradients.
gradients = opt.compute_gradients(
loss,
variables,
colocate_gradients_with_ops=colocate_gradients_with_ops)
# Optionally add gradient noise.
if gradient_noise_scale is not None:
gradients = _add_scaled_noise_to_gradients(gradients,
gradient_noise_scale)
# Multiply some gradients.
if gradient_multipliers is not None:
gradients = _multiply_gradients(gradients, gradient_multipliers)
if not gradients:
raise ValueError(
"Empty list of (gradient, var) pairs encountered. This is most "
"likely to be caused by an improper value of gradient_multipliers.")
if "gradient_norm" in summaries:
summary.scalar("global_norm/gradient_norm",
clip_ops.global_norm(list(zip(*gradients))[0]))
# Optionally clip gradients by global norm.
if isinstance(clip_gradients, float):
gradients = _clip_gradients_by_norm(gradients, clip_gradients)
elif callable(clip_gradients):
gradients = clip_gradients(gradients)
elif clip_gradients is not None:
raise ValueError(
"Unknown type %s for clip_gradients" % type(clip_gradients))
# Add scalar summary for loss.
if "loss" in summaries:
summary.scalar("loss", loss)
# Add histograms for variables, gradients and gradient norms.
for gradient, variable in gradients:
if isinstance(gradient, ops.IndexedSlices):
grad_values = gradient.values
else:
grad_values = gradient
if grad_values is not None:
var_name = variable.name.replace(":", "_")
if "gradients" in summaries:
summary.histogram("gradients/%s" % var_name, grad_values)
if "gradient_norm" in summaries:
summary.scalar("gradient_norm/%s" % var_name,
clip_ops.global_norm([grad_values]))
if clip_gradients is not None and "gradient_norm" in summaries:
summary.scalar("global_norm/clipped_gradient_norm",
clip_ops.global_norm(list(zip(*gradients))[0]))
# Create gradient updates.
grad_updates = opt.apply_gradients(
gradients,
global_step=global_step if increment_global_step else None,
name="train")
# Ensure the train_tensor computes grad_updates.
train_tensor = control_flow_ops.with_dependencies([grad_updates], loss)
return train_tensor
def optimize_loss(loss,
global_step,
learning_rate,
optimizer,
gradient_noise_scale=None,
gradient_multipliers=None,
clip_gradients=None,
learning_rate_decay_fn=None,
update_ops=None,
variables=None,
name=None,
summaries=None,
colocate_gradients_with_ops=False):
"""Given loss and parameters for optimizer, returns a training op.
Various ways of passing optimizers, include:
- string, name of the optimizer like 'SGD', 'Adam', see OPTIMIZER_CLS_NAMES
for full list. E.g. `optimize_loss(..., optimizer='Adam')`.
- function, takes learning rate `Tensor` as argument and must return
`Optimizer` instance. E.g. `optimize_loss(...,
optimizer=lambda lr: tf.train.MomentumOptimizer(lr, momentum=0.5))`.
Alternatively, if `learning_rate` is `None`, the function takes no
arguments. E.g. `optimize_loss(..., learning_rate=None,
optimizer=lambda: tf.train.MomentumOptimizer(0.5, momentum=0.5))`.
- class, subclass of `Optimizer` that takes only one required argument -
learning rate, such as AdamOptimizer, AdagradOptimizer.
E.g. `optimize_loss(..., optimizer=tf.train.AdagradOptimizer)`.
- object, instance of subclass of `Optimizer`.
E.g., `optimizer_loss(..., optimizer=tf.train.AdagradOptimizer(0.5))`.
Args:
loss: Scalar `Tensor`.
global_step: Scalar int `Tensor`, step counter for each update. If not
supplied, it will be fetched from the default graph (see
`tf.contrib.framework.get_global_step` for details). If it's
not been created, no step will be incremented with each weight
update. `learning_rate_decay_fn` requires `global_step`.
learning_rate: float or `Tensor`, magnitude of update per each training
step. Can be `None`.
optimizer: string, class or optimizer instance, used as trainer.
string should be name of optimizer, like 'SGD',
'Adam', 'Adagrad'. Full list in OPTIMIZER_CLS_NAMES constant.
class should be sub-class of `tf.Optimizer` that implements
`compute_gradients` and `apply_gradients` functions.
optimizer instance should be instantiation of `tf.Optimizer`
sub-class and have `compute_gradients` and `apply_gradients`
functions.
gradient_noise_scale: float or None, adds 0-mean normal noise scaled by this
value.
gradient_multipliers: dict of variables or variable names to floats.
If present, gradients for specified
variables will be multiplied by given constant.
clip_gradients: float, callable or `None`. If float, is provided, a global
clipping is applied to prevent the norm of the gradient to exceed this
value. Alternatively, a callable can be provided e.g.: adaptive_clipping.
This callable takes a `list` of `(gradients, variables)` `tuple`s and
returns the same thing with the gradients modified.
learning_rate_decay_fn: function, takes `learning_rate` and `global_step`
`Tensor`s, returns `Tensor`.
Can be used to implement any learning rate decay
functions.
For example: `tf.train.exponential_decay`.
Ignored if `learning_rate` is not supplied.
update_ops: list of update `Operation`s to execute at each step. If `None`,
uses elements of UPDATE_OPS collection. The order of execution
between `update_ops` and `loss` is non-deterministic.
variables: list of variables to optimize or
`None` to use all trainable variables.
name: The name for this operation is used to scope operations and summaries.
summaries: List of internal quantities to visualize on tensorboard. If not
set only the loss and the learning rate will be reported. The
complete list is in OPTIMIZER_SUMMARIES.
colocate_gradients_with_ops: If True, try colocating gradients with the
corresponding op.
Returns:
Training op.
Raises:
ValueError: if:
* `loss` is an invalid type or shape.
* `global_step` is an invalid type or shape.
* `learning_rate` is an invalid type or value.
* `optimizer` is wrong type.
* `clip_gradients` is not float or callable.
* `learning_rate` and `learning_rate_decay_fn` are supplied, but no
`global_step` is available.
"""
loss = ops.convert_to_tensor(loss)
contrib_framework.assert_scalar(loss)
if global_step is None:
global_step = contrib_framework.get_global_step()
else:
contrib_framework.assert_global_step(global_step)
with vs.variable_scope(name, "OptimizeLoss", [loss, global_step]):
# Update ops take UPDATE_OPS collection if not provided.
if update_ops is None:
update_ops = set(ops.get_collection(ops.GraphKeys.UPDATE_OPS))
# Make sure update ops are ran before computing loss.
if update_ops:
loss = control_flow_ops.with_dependencies(list(update_ops), loss)
# Learning rate variable, with possible decay.
lr = None
if learning_rate is not None:
if (isinstance(learning_rate, ops.Tensor)
and learning_rate.get_shape().ndims == 0):
lr = learning_rate
elif isinstance(learning_rate, float):
if learning_rate < 0.0:
raise ValueError("Invalid learning_rate %s.",
learning_rate)
lr = vs.get_variable(
"learning_rate", [],
trainable=False,
initializer=init_ops.constant_initializer(learning_rate))
else:
raise ValueError(
"Learning rate should be 0d Tensor or float. "
"Got %s of type %s" %
(str(learning_rate), str(type(learning_rate))))
if summaries is None:
summaries = ["loss", "learning_rate"]
else:
for summ in summaries:
if summ not in OPTIMIZER_SUMMARIES:
raise ValueError(
"Summaries should be one of [%s], you provided %s." %
(", ".join(OPTIMIZER_SUMMARIES), summ))
if learning_rate is not None and learning_rate_decay_fn is not None:
if global_step is None:
raise ValueError(
"global_step is required for learning_rate_decay_fn.")
lr = learning_rate_decay_fn(lr, global_step)
if "learning_rate" in summaries:
summary.scalar("learning_rate", lr)
# Create optimizer, given specified parameters.
if isinstance(optimizer, six.string_types):
if lr is None:
raise ValueError(
"Learning rate is None, but should be specified if "
"optimizer is string (%s)." % optimizer)
if optimizer not in OPTIMIZER_CLS_NAMES:
raise ValueError(
"Optimizer name should be one of [%s], you provided %s." %
(", ".join(OPTIMIZER_CLS_NAMES), optimizer))
opt = OPTIMIZER_CLS_NAMES[optimizer](learning_rate=lr)
elif (isinstance(optimizer, type)
and issubclass(optimizer, optimizer_.Optimizer)):
if lr is None:
raise ValueError(
"Learning rate is None, but should be specified if "
"optimizer is class (%s)." % optimizer)
opt = optimizer(learning_rate=lr)
elif isinstance(optimizer, optimizer_.Optimizer):
opt = optimizer
elif callable(optimizer):
if learning_rate is not None:
opt = optimizer(lr)
else:
opt = optimizer()
if not isinstance(opt, optimizer_.Optimizer):
raise ValueError(
"Unrecognized optimizer: function should return "
"subclass of Optimizer. Got %s." % str(opt))
else:
raise ValueError(
"Unrecognized optimizer: should be string, "
"subclass of Optimizer, instance of "
"subclass of Optimizer or function with one argument. "
"Got %s." % str(optimizer))
# All trainable variables, if specific variables are not specified.
if variables is None:
variables = vars_.trainable_variables()
# Compute gradients.
gradients = opt.compute_gradients(
loss,
variables,
colocate_gradients_with_ops=colocate_gradients_with_ops)
# Optionally add gradient noise.
if gradient_noise_scale is not None:
gradients = _add_scaled_noise_to_gradients(gradients,
gradient_noise_scale)
# Multiply some gradients.
if gradient_multipliers is not None:
gradients = _multiply_gradients(gradients, gradient_multipliers)
if "gradient_norm" in summaries:
summary.scalar("global_norm/gradient_norm",
clip_ops.global_norm(list(zip(*gradients))[0]))
# Optionally clip gradients by global norm.
if isinstance(clip_gradients, float):
gradients = _clip_gradients_by_norm(gradients, clip_gradients)
elif callable(clip_gradients):
gradients = clip_gradients(gradients)
elif clip_gradients is not None:
raise ValueError("Unknown type %s for clip_gradients" %
type(clip_gradients))
# Add scalar summary for loss.
if "loss" in summaries:
summary.scalar("loss", loss)
# Add histograms for variables, gradients and gradient norms.
for gradient, variable in gradients:
if isinstance(gradient, ops.IndexedSlices):
grad_values = gradient.values
else:
grad_values = gradient
if grad_values is not None:
var_name = variable.name.replace(":", "_")
if "gradients" in summaries:
summary.histogram("gradients/%s" % var_name, grad_values)
if "gradient_norm" in summaries:
summary.scalar("gradient_norm/%s" % var_name,
clip_ops.global_norm([grad_values]))
if clip_gradients is not None and "gradient_norm" in summaries:
summary.scalar("global_norm/clipped_gradient_norm",
clip_ops.global_norm(list(zip(*gradients))[0]))
# Create gradient updates.
grad_updates = opt.apply_gradients(gradients,
global_step=global_step,
name="train")
# Ensure the train_tensor computes grad_updates.
train_tensor = control_flow_ops.with_dependencies([grad_updates], loss)
return train_tensor