0b8f0a5b84
- experimental_run_v2 -> run PiperOrigin-RevId: 300574367 Change-Id: I5d82ea5450a4d32aea6d05ed3db4f02b8edb2eea
349 lines
11 KiB
Python
349 lines
11 KiB
Python
# Copyright 2018 The TensorFlow Authors. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ==============================================================================
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"""Utility to get tf.distribute.Strategy related contexts."""
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from __future__ import absolute_import
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from __future__ import division
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from __future__ import print_function
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import contextlib
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import threading
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from tensorflow.python.framework import ops
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from tensorflow.python.util.lazy_loader import LazyLoader
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from tensorflow.python.util.tf_export import tf_export
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# There is a circular dependency between this and the `distribute_lib` module.
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# So we load it lazily to work around this.
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distribute_lib = LazyLoader(
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"distribute_lib", globals(),
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"tensorflow.python.distribute.distribute_lib")
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# ------------------------------------------------------------------------------
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# Internal API for setting the current thread mode as being either in a
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# replica or cross-replica context for a particular tf.distribute.Strategy.
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class _ThreadMode(object):
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def __init__(self, dist, cross, replica):
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self.strategy = dist
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self.cross_replica_context = cross
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self.replica_context = replica
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class _CrossReplicaThreadMode(_ThreadMode):
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def __init__(self, strategy):
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_ThreadMode.__init__(self, strategy, strategy, None)
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class _InReplicaThreadMode(_ThreadMode):
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def __init__(self, replica_ctx):
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_ThreadMode.__init__(self, replica_ctx.strategy, None, replica_ctx)
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def _push_per_thread_mode(context):
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ops.get_default_graph()._distribution_strategy_stack.append(context) # pylint: disable=protected-access
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def _pop_per_thread_mode():
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ops.get_default_graph()._distribution_strategy_stack.pop(-1) # pylint: disable=protected-access
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class _DefaultReplicaThreadMode(_ThreadMode):
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"""Type of default value returned by `_get_per_thread_mode()`.
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Used when the thread-local stack is empty.
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"""
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def __init__(self):
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_ThreadMode.__init__(self, _get_default_strategy(), None,
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_get_default_replica_context())
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def _get_per_thread_mode():
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try:
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return ops.get_default_graph()._distribution_strategy_stack[-1] # pylint: disable=protected-access
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except (AttributeError, IndexError):
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return _get_default_replica_mode()
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# ------------------------------------------------------------------------------
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# Public API for accessing the current thread mode
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@tf_export("distribute.get_replica_context")
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def get_replica_context():
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"""Returns the current `tf.distribute.ReplicaContext` or `None`.
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Returns `None` if in a cross-replica context.
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Note that execution:
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1. starts in the default (single-replica) replica context (this function
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will return the default `ReplicaContext` object);
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2. switches to cross-replica context (in which case this will return
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`None`) when entering a `with tf.distribute.Strategy.scope():` block;
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3. switches to a (non-default) replica context inside `strategy.run(fn, ...)`;
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4. if `fn` calls `get_replica_context().merge_call(merge_fn, ...)`, then
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inside `merge_fn` you are back in the cross-replica context (and again
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this function will return `None`).
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Most `tf.distribute.Strategy` methods may only be executed in
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a cross-replica context, in a replica context you should use the
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API of the `tf.distribute.ReplicaContext` object returned by this
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method instead.
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```
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assert tf.distribute.get_replica_context() is not None # default
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with strategy.scope():
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assert tf.distribute.get_replica_context() is None
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def f():
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replica_context = tf.distribute.get_replica_context() # for strategy
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assert replica_context is not None
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tf.print("Replica id: ", replica_context.replica_id_in_sync_group,
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" of ", replica_context.num_replicas_in_sync)
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strategy.run(f)
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```
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Returns:
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The current `tf.distribute.ReplicaContext` object when in a replica context
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scope, else `None`.
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Within a particular block, exactly one of these two things will be true:
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* `get_replica_context()` returns non-`None`, or
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* `tf.distribute.is_cross_replica_context()` returns True.
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"""
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return _get_per_thread_mode().replica_context
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def get_cross_replica_context():
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"""Returns the current tf.distribute.Strategy if in a cross-replica context.
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DEPRECATED: Please use `in_cross_replica_context()` and
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`get_strategy()` instead.
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Returns:
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Returns the current `tf.distribute.Strategy` object in a cross-replica
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context, or `None`.
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Exactly one of `get_replica_context()` and `get_cross_replica_context()`
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will return `None` in a particular block.
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"""
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return _get_per_thread_mode().cross_replica_context
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@tf_export("distribute.in_cross_replica_context")
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def in_cross_replica_context():
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"""Returns `True` if in a cross-replica context.
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See `tf.distribute.get_replica_context` for details.
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```
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assert not tf.distribute.in_cross_replica_context()
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with strategy.scope():
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assert tf.distribute.in_cross_replica_context()
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def f():
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assert not tf.distribute.in_cross_replica_context()
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strategy.run(f)
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```
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Returns:
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`True` if in a cross-replica context (`get_replica_context()` returns
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`None`), or `False` if in a replica context (`get_replica_context()` returns
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non-`None`).
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"""
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return _get_per_thread_mode().cross_replica_context is not None
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@tf_export("distribute.get_strategy")
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def get_strategy():
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"""Returns the current `tf.distribute.Strategy` object.
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Typically only used in a cross-replica context:
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```
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if tf.distribute.in_cross_replica_context():
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strategy = tf.distribute.get_strategy()
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...
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```
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Returns:
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A `tf.distribute.Strategy` object. Inside a `with strategy.scope()` block,
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it returns `strategy`, otherwise it returns the default (single-replica)
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`tf.distribute.Strategy` object.
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"""
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return _get_per_thread_mode().strategy
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@tf_export("distribute.has_strategy")
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def has_strategy():
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"""Return if there is a current non-default `tf.distribute.Strategy`.
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```
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assert not tf.distribute.has_strategy()
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with strategy.scope():
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assert tf.distribute.has_strategy()
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```
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Returns:
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True if inside a `with strategy.scope():`.
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"""
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return get_strategy() is not _get_default_strategy()
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def get_strategy_and_replica_context():
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per_thread_mode = _get_per_thread_mode()
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return (per_thread_mode.strategy, per_thread_mode.replica_context)
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@tf_export("distribute.experimental_set_strategy")
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def experimental_set_strategy(strategy):
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"""Set a `tf.distribute.Strategy` as current without `with strategy.scope()`.
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```
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tf.distribute.experimental_set_strategy(strategy1)
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f()
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tf.distribute.experimental_set_strategy(strategy2)
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g()
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tf.distribute.experimental_set_strategy(None)
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h()
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```
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is equivalent to:
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```
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with strategy1.scope():
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f()
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with strategy2.scope():
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g()
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h()
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```
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In general, you should use the `with strategy.scope():` API, but this
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alternative may be convenient in notebooks where you would have to put
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each cell in a `with strategy.scope():` block.
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Note: This should only be called outside of any TensorFlow scope to
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avoid improper nesting.
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Args:
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strategy: A `tf.distribute.Strategy` object or None.
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Raises:
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RuntimeError: If called inside a `with strategy.scope():`.
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"""
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old_scope = ops.get_default_graph()._global_distribute_strategy_scope # pylint: disable=protected-access
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if old_scope is not None:
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old_scope.__exit__(None, None, None)
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ops.get_default_graph()._global_distribute_strategy_scope = None # pylint: disable=protected-access
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if has_strategy():
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raise RuntimeError(
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"Must not be called inside a `tf.distribute.Strategy` scope.")
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if strategy is not None:
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new_scope = strategy.scope()
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new_scope.__enter__()
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ops.get_default_graph()._global_distribute_strategy_scope = new_scope # pylint: disable=protected-access
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# ------------------------------------------------------------------------------
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# Internal helpers.
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@contextlib.contextmanager
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def enter_or_assert_strategy(strategy):
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if not has_strategy():
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with strategy.scope():
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yield
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else:
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_assert_strategy(strategy)
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yield
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# ------------------------------------------------------------------------------
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# Defaults that are used when no tf.distribute.Strategy is explicitly created.
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# We create them lazily in a function so that we can workaround the circular
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# dependency on distribute_lib. See lazy loader at the top of this file.
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_defaults = {
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"strategy": None,
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"replica_context": None,
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"replica_mode": None
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}
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# Note: These need to be different locks since _get_default_replica_context
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# calls _get_default_strategy inside its lock, and them using the same lock
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# can lead to deadlock.
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_default_strategy_lock = threading.Lock()
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_default_replica_context_lock = threading.Lock()
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_default_replica_mode_lock = threading.Lock()
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def _assert_strategy(strategy):
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if not has_strategy():
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raise RuntimeError('Need to be inside "with strategy.scope()" for %s' %
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(strategy,))
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current_strategy = get_strategy()
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if current_strategy is not strategy:
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raise RuntimeError(
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"Mixing different tf.distribute.Strategy objects: %s is not %s" %
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(current_strategy, strategy))
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def _get_default_strategy():
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if _defaults["strategy"] is None:
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# Avoid race condition causing two defaults to be created
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with _default_strategy_lock:
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if _defaults["strategy"] is None:
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# pylint: disable=protected-access
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# Make sure distribute_lib module is loaded by accessing some member.
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_ = distribute_lib._creating_default_strategy_singleton
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distribute_lib._creating_default_strategy_singleton = True
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_defaults["strategy"] = distribute_lib._DefaultDistributionStrategy()
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distribute_lib._creating_default_strategy_singleton = False
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# pylint: enable=protected-access
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return _defaults["strategy"]
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def _get_default_replica_context():
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if _defaults["replica_context"] is None:
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# Avoid race condition causing two defaults to be created
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with _default_replica_context_lock:
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if _defaults["replica_context"] is None:
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_defaults["replica_context"] = distribute_lib.ReplicaContext(
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_get_default_strategy(), replica_id_in_sync_group=0)
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return _defaults["replica_context"]
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def _get_default_replica_mode():
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if _defaults["replica_mode"] is None:
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# Avoid race condition causing two defaults to be created
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with _default_replica_mode_lock:
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if _defaults["replica_mode"] is None:
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_defaults["replica_mode"] = _DefaultReplicaThreadMode()
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return _defaults["replica_mode"]
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# Aliases for compatibility with old names.
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get_distribution_strategy = get_strategy
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has_distribution_strategy = has_strategy
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