| # Copyright 2017 The TensorFlow Authors. 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. |
| # ============================================================================== |
| """Gradient tape utilities.""" |
| |
| from tensorflow.python import pywrap_tfe |
| |
| |
| class Tape(object): |
| """Represents a gradient propagation trace.""" |
| |
| __slots__ = ["_tape"] |
| |
| def __init__(self, tape): |
| self._tape = tape |
| |
| def watched_variables(self): |
| return pywrap_tfe.TFE_Py_TapeWatchedVariables(self._tape) |
| |
| |
| def push_new_tape(persistent=False, watch_accessed_variables=True): |
| """Pushes a new tape onto the tape stack.""" |
| tape = pywrap_tfe.TFE_Py_TapeSetNew(persistent, watch_accessed_variables) |
| return Tape(tape) |
| |
| |
| def push_tape(tape): |
| """Pushes an existing tape onto the tape stack.""" |
| pywrap_tfe.TFE_Py_TapeSetAdd(tape._tape) # pylint: disable=protected-access |
| |
| |
| def watch(tape, tensor): |
| """Marks this tensor to be watched by the given tape.""" |
| pywrap_tfe.TFE_Py_TapeWatch(tape._tape, tensor) # pylint: disable=protected-access |
| |
| |
| def default_get_variables(variable): |
| return [variable] |
| |
| # Gets a list of changed variables. Can be overriden using |
| # register_variables_override. An example of overriding is for getting the |
| # varibles within a distributed context. |
| _variables_override = default_get_variables |
| |
| |
| def register_watched_variable_resolver(resolver): |
| """Registers the resolver to be used to get the list of variables to watch. |
| |
| Args: |
| resolver: callable, takes a Variable and returns a list of Variables that |
| shall be watched. |
| """ |
| global _variables_override |
| assert _variables_override is default_get_variables |
| _variables_override = resolver |
| |
| |
| def watch_variable(tape, variable): |
| """Marks this variable to be watched by the given tape.""" |
| variables = _variables_override(variable) |
| for var in variables: |
| pywrap_tfe.TFE_Py_TapeWatchVariable(tape._tape, var) # pylint: disable=protected-access |
| pywrap_tfe.TFE_Py_VariableWatcherVariableAccessed(var) |
| |
| |
| def variable_accessed(variable): |
| """Notifies all tapes in the stack that a variable has been accessed. |
| |
| Args: |
| variable: variable to be watched. |
| """ |
| variables = _variables_override(variable) |
| for var in variables: |
| pywrap_tfe.TFE_Py_TapeVariableAccessed(var) |
| pywrap_tfe.TFE_Py_VariableWatcherVariableAccessed(var) |
| |
| |
| def variables_accessed(variables): |
| """Notifies all tapes in the stack that variables have been accessed. |
| |
| Only trainable variables are marked as accessed. |
| |
| Args: |
| variables: iterable of variables to mark as accessed. |
| """ |
| accessed = [] |
| for variable in variables: |
| if variable.trainable: |
| accessed.extend(_variables_override(variable)) |
| |
| for var in accessed: |
| pywrap_tfe.TFE_Py_TapeVariableAccessed(var) |
| pywrap_tfe.TFE_Py_VariableWatcherVariableAccessed(var) |
| |
| |
| def pop_tape(tape): |
| """Pops the given tape in the stack.""" |
| pywrap_tfe.TFE_Py_TapeSetRemove(tape._tape) # pylint: disable=protected-access |