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__init__.py
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__init__.py
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# Copyright 2017 Uber Technologies, Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
from packaging import version
import horovod.tensorflow as hvd
import tensorflow as tf
from horovod.tensorflow.gradient_aggregation import LocalGradientAggregationHelper
from horovod.tensorflow.gradient_aggregation_eager import LocalGradientAggregationHelperEager
from horovod.tensorflow.mpi_ops import rank
_PRE_TF_2_4_0 = version.parse(tf.__version__) < version.parse('2.4.0')
def create_distributed_optimizer(keras, optimizer, name, device_dense, device_sparse,
compression, sparse_as_dense, gradient_predivide_factor,
op, backward_passes_per_step=1,
average_aggregated_gradients=False,
groups=None, process_set=hvd.global_process_set):
class _DistributedOptimizer(keras.optimizers.Optimizer):
_HAS_AGGREGATE_GRAD = True
def __init__(self, **kwargs):
super(self.__class__, self).__init__(**kwargs)
self._name = name or "Distributed%s" % self.__class__.__base__.__name__
self._aggregated_gradients = False
self._allreduce_grads = hvd._make_allreduce_grads_fn(
self._name,
device_dense,
device_sparse,
compression,
sparse_as_dense,
op,
gradient_predivide_factor,
groups,
process_set=process_set)
self._agg_helper = None
if backward_passes_per_step > 1:
if hvd._executing_eagerly():
self._agg_helper = LocalGradientAggregationHelperEager(
backward_passes_per_step=backward_passes_per_step,
allreduce_func=self._allreduce_grads,
sparse_as_dense=sparse_as_dense,
average_aggregated_gradients=average_aggregated_gradients,
)
else:
self._agg_helper = LocalGradientAggregationHelper(
backward_passes_per_step=backward_passes_per_step,
allreduce_func=self._allreduce_grads,
sparse_as_dense=sparse_as_dense,
average_aggregated_gradients=average_aggregated_gradients,
rank=rank(),
optimizer_type=LocalGradientAggregationHelper._OPTIMIZER_TYPE_KERAS,
)
def _compute_gradients(self, loss, var_list, grad_loss=None, tape=None):
"""
Compute gradients of all trainable variables.
See Optimizer.get_gradients() for more info.
In DistributedOptimizer, get_gradients() is overriden to also
allreduce the gradients before returning them.
"""
if _PRE_TF_2_4_0:
return super(self.__class__, self)._compute_gradients(
loss, var_list, grad_loss, tape)
tape = tf.GradientTape() if tape is None else tape
grads_and_vars = super(self.__class__, self)._compute_gradients(
# pylint: disable=protected-access
loss,
var_list,
grad_loss,
tape=tape)
grads, weights = list(zip(*grads_and_vars))
allreduced_grads = self._allreduce(grads, weights)
return list(zip(allreduced_grads, weights))
def get_gradients(self, loss, params):
"""
Compute gradients of all trainable variables.
See Optimizer.get_gradients() for more info.
In DistributedOptimizer, get_gradients() is overriden to also
allreduce the gradients before returning them.
"""
gradients = super(self.__class__, self).get_gradients(loss, params)
return self._allreduce(gradients, params)
def _aggregate_gradients(self, grads_and_vars):
if _PRE_TF_2_4_0:
grads, vars = list(zip(*grads_and_vars))
aggregated_grads = self._allreduce(grads, vars)
return aggregated_grads
else:
return super(self.__class__, self)._aggregate_gradients(
grads_and_vars)
def _allreduce(self, grads, vars):
self._aggregated_gradients = True
if self._agg_helper:
return self._agg_helper.compute_gradients(tuple(grads), tuple(vars))
else:
return self._allreduce_grads(grads, vars)
def apply_gradients(self, *args, **kwargs):
if self._agg_helper:
if isinstance(args[0], zip):
# If grad_and_vars are passed in as a zip object
# convert to a list. This is necessary for TF2.4+
# b/c args[0] is used in both conditional branches
# inside _agg_helper.apply_gradients().
args = list(args)
args[0] = list(args[0])
args = tuple(args)
results = self._agg_helper.apply_gradients(
lambda: super(self.__class__, self).apply_gradients(*args, **kwargs),
self,
*args,
**kwargs,
)
else:
results = super(self.__class__, self).apply_gradients(*args, **kwargs)
if _PRE_TF_2_4_0 and not self._aggregated_gradients:
raise Exception('`apply_gradients()` was called without a call to '
'`get_gradients()` or `_aggregate_gradients`. If you\'re '
'using TensorFlow 2.0, please specify '
'`experimental_run_tf_function=False` in `compile()`.')
return results
# We dynamically create a new class that inherits from the optimizer that was passed in.
# The goal is to override get_gradients() method with an allreduce implementation.
# This class will have the same name as the optimizer it's wrapping, so that the saved
# model could be easily restored without Horovod.
cls = type(optimizer.__class__.__name__, (optimizer.__class__,),
dict(_DistributedOptimizer.__dict__))
return cls.from_config(optimizer.get_config())
def _eval(backend, op_or_result):
if hvd._executing_eagerly():
return op_or_result
else:
return backend.get_session().run(op_or_result)
if hasattr(hvd, 'broadcast_global_variables'):
def broadcast_global_variables(backend, root_rank):
return _eval(backend, hvd.broadcast_global_variables(root_rank))
def allreduce(backend, value, name, average, prescale_factor, postscale_factor, op, compression):
return _eval(backend, hvd.allreduce(tf.constant(value, name=name), average=average,
prescale_factor=prescale_factor,
postscale_factor=postscale_factor,
op=op, compression=compression))
def allgather(backend, value, name):
return _eval(backend, hvd.allgather(tf.constant(value, name=name)))
def broadcast(backend, value, root_rank, name):
return _eval(backend, hvd.broadcast(tf.constant(value, name=name), root_rank))
def reducescatter(backend, value, name, op):
return _eval(backend, hvd.reducescatter(tf.constant(value, name=name), op=op))
def load_model(keras, wrap_optimizer, optimizer_modules, filepath, custom_optimizers, custom_objects):
horovod_objects = {
subclass.__name__.lower(): wrap_optimizer(subclass)
for subclass in keras.optimizers.Optimizer.__subclasses__()
if subclass.__module__ in optimizer_modules
}
if custom_optimizers is not None:
horovod_objects.update({
cls.__name__: wrap_optimizer(cls)
for cls in custom_optimizers
})
if custom_objects is not None:
horovod_objects.update(custom_objects)
return keras.models.load_model(filepath, custom_objects=horovod_objects)