75 lines
2.6 KiB
Python
75 lines
2.6 KiB
Python
# Copyright 2019 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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"""Utilities for managing forward accumulators.
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A separate file from forwardprop.py so that functions can use these utilities.
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"""
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import collections
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import contextlib
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from tensorflow.python import pywrap_tfe
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class TangentInfo(
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collections.namedtuple("TangentInfo", ["indices", "tangents"])):
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"""Packed forward accumulator state. The return value of `pack_tangents`."""
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def __new__(cls, indices=None, tangents=None):
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if indices is None:
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indices = ()
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if tangents is None:
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tangents = []
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return super(TangentInfo, cls).__new__(cls, indices, tangents)
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def pack_tangents(tensors):
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"""Packs forward accumulator state into a TangentInfo tuple.
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Args:
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tensors: A flat list of Tensors to pack forward accumulator state for.
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Returns:
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A tuple of (indices, tangents):
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indices: A sequence of sequences of two-element tuples. Each forward
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accumulator is represented as a sequence of tuples with (primal_index,
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jvp_index). Both integers index into the concatenated `tensors + jvps`
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array.
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tangents: A flat list of Tensors. Best interpreted as a sequence to be
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appended to `tensors`.
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"""
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return TangentInfo(*pywrap_tfe.TFE_Py_PackJVPs(tensors))
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@contextlib.contextmanager
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def push_forwardprop_state():
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"""Temporarily push or pop transient state for accumulators in the active set.
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Allows an accumulator which is currently processing an operation to
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temporarily reset its state. This is useful when building forwardprop versions
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of functions, where an accumulator will trigger function building and then
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must process captured symbolic tensors while building it. Without pushing and
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popping, accumulators ignore operations executed as a direct result of their
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own jvp computations.
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Yields:
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None (used for its side effect).
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"""
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try:
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pywrap_tfe.TFE_Py_ForwardAccumulatorPushState()
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yield
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finally:
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pywrap_tfe.TFE_Py_ForwardAccumulatorPopState()
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