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# Copyright 2016 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.
# ==============================================================================
"""Converter for list operations.
This includes converting Python lists to TensorArray/TensorList.
"""
# TODO(mdan): Elaborate the logic here.
# TODO(mdan): Does it even make sense to attempt to try to use TAs?
# The current rule (always convert to TensorArray) is naive and insufficient.
# In general, a better mechanism could look like:
# * convert to TensorList by default
# * leave as Python list if the user explicitly forbids it
# * convert to TensorArray only when complete write once behavior can be
# guaranteed (e.g. list comprehensions)
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import gast
from tensorflow.contrib.autograph.core import converter
from tensorflow.contrib.autograph.lang import directives
from tensorflow.contrib.autograph.pyct import anno
from tensorflow.contrib.autograph.pyct import parser
from tensorflow.contrib.autograph.pyct import templates
from tensorflow.contrib.autograph.pyct.static_analysis.annos import NodeAnno
# Tags for local state.
POP_USES = 'pop_uses'
class ListTransformer(converter.Base):
"""Converts lists and related operations to their TF counterpart."""
def visit_List(self, node):
node = self.generic_visit(node)
template = """
ag__.new_list(elements)
"""
return templates.replace_as_expression(template, elements=node)
def _replace_append_call(self, node):
assert len(node.args) == 1
assert isinstance(node.func, gast.Attribute)
template = """
target = ag__.list_append(target, element)
"""
return templates.replace(
template,
target=node.func.value,
element=node.args[0])
def _replace_pop_call(self, node):
# Expressions that use pop() are converted to a statement + expression.
#
# For example:
#
# print(target.pop())
#
# ... is converted to:
#
# target, target_pop = ag__.list_pop(target)
# print(target_pop)
#
# Here, we just generate the variable name and swap it in,
# and _generate_pop_operation will handle the rest.
#
# Multiple uses of pop() are allowed:
#
# print(tartget.pop(), target.pop())
# print(tartget.pop().pop())
#
assert isinstance(node.func, gast.Attribute)
scope = anno.getanno(node, NodeAnno.ARGS_SCOPE)
target_node = node.func.value
# Attempt to use a related name if one exists. Otherwise use something
# generic.
if anno.hasanno(target_node, anno.Basic.QN):
target_name = anno.getanno(target_node, anno.Basic.QN).ssf()
else:
target_name = 'list_'
pop_var_name = self.ctx.namer.new_symbol(target_name, scope.referenced)
pop_uses = self.get_local(POP_USES, [])
pop_uses.append((node, pop_var_name))
self.set_local(POP_USES, pop_uses)
return templates.replace_as_expression('var_name', var_name=pop_var_name)
def _replace_stack_call(self, node):
assert len(node.args) == 1
dtype = self.get_definition_directive(
node.args[0],
directives.set_element_type,
'dtype',
default=templates.replace_as_expression('None'))
template = """
ag__.list_stack(
target,
opts=ag__.ListStackOpts(
element_dtype=dtype,
original_call=orig_call))
"""
return templates.replace_as_expression(
template,
dtype=dtype,
target=node.args[0],
orig_call=node.func)
def visit_Call(self, node):
node = self.generic_visit(node)
# TODO(mdan): This is insufficient if target is a function argument.
# In the case of function arguments, we need to add the list to the
# function's return value, because it is being modified.
# TODO(mdan): Checking just the name is brittle, can it be improved?
if isinstance(node.func, gast.Attribute):
func_name = node.func.attr
if func_name == 'append' and (len(node.args) == 1):
node = self._replace_append_call(node)
elif func_name == 'pop' and (len(node.args) <= 1):
node = self._replace_pop_call(node)
elif (func_name == 'stack' and (len(node.args) == 1) and
(not node.keywords or node.keywords[0].arg == 'strict')):
# This avoids false positives with keyword args.
# TODO(mdan): handle kwargs properly.
node = self._replace_stack_call(node)
return node
def _generate_pop_operation(self, original_call_node, pop_var_name):
assert isinstance(original_call_node.func, gast.Attribute)
if original_call_node.args:
pop_element = original_call_node.args[0]
else:
pop_element = parser.parse_expression('None')
# The call will be something like "target.pop()", and the dtype is hooked to
# target, hence the func.value.
# TODO(mdan): For lists of lists, this won't work.
# The reason why it won't work is because it's unclear how to annotate
# the list as a "list of lists with a certain element type" when using
# operations like `l.pop().pop()`.
dtype = self.get_definition_directive(
original_call_node.func.value,
directives.set_element_type,
'dtype',
default=templates.replace_as_expression('None'))
shape = self.get_definition_directive(
original_call_node.func.value,
directives.set_element_type,
'shape',
default=templates.replace_as_expression('None'))
template = """
target, pop_var_name = ag__.list_pop(
target, element,
opts=ag__.ListPopOpts(element_dtype=dtype, element_shape=shape))
"""
return templates.replace(
template,
target=original_call_node.func.value,
pop_var_name=pop_var_name,
element=pop_element,
dtype=dtype,
shape=shape)
def _postprocess_statement(self, node):
"""Inserts any separate pop() calls that node may use."""
pop_uses = self.get_local(POP_USES, None)
if pop_uses:
replacements = []
for original_call_node, pop_var_name in pop_uses:
replacements.extend(
self._generate_pop_operation(original_call_node, pop_var_name))
replacements.append(node)
node = replacements
self.exit_local_scope()
return node, None
# TODO(mdan): Should we have a generic visit_block instead?
# Right now it feels that a visit_block would add too much magic that's
# hard to follow.
def _visit_and_process_block(self, block):
return self.visit_block(
block,
before_visit=self.enter_local_scope,
after_visit=self._postprocess_statement)
def visit_FunctionDef(self, node):
node.args = self.generic_visit(node.args)
node.decorator_list = self.visit_block(node.decorator_list)
node.body = self._visit_and_process_block(node.body)
return node
def visit_For(self, node):
node.target = self.visit(node.target)
node.body = self._visit_and_process_block(node.body)
node.orelse = self._visit_and_process_block(node.orelse)
return node
def visit_While(self, node):
node.test = self.visit(node.test)
node.body = self._visit_and_process_block(node.body)
node.orelse = self._visit_and_process_block(node.orelse)
return node
def visit_If(self, node):
node.test = self.visit(node.test)
node.body = self._visit_and_process_block(node.body)
node.orelse = self._visit_and_process_block(node.orelse)
return node
def visit_With(self, node):
node.items = self.visit_block(node.items)
node.body = self._visit_and_process_block(node.body)
return node
def transform(node, ctx):
return ListTransformer(ctx).visit(node)
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