Class _ContextSwitchStack

tensorflow/python/eager/context.py:199–237

A thread-local stack of context switches.

# `_ContextSwitchStack` is a `threading.local` to match the semantics of
# ``DefaultGraphStack`, which is also a `threading.local`.
class _ContextSwitchStack(threading.local):
  """A thread-local stack of context switches."""

  def __init__(self, eager):
    super(_ContextSwitchStack, self).__init__()
    self.stack = []
    if eager:
      # Initialize the stack with a pointer to enter the eager context; this
      # ensures that the fact that eager execution was enabled is propagated
      # across threads, since (1) `enable_eager_execution` modifies a
      # process-level flag (`default_execution_mode`) and (2) `__init__` is
      # called each time a threading.local object is used in a separate thread.
      self.push(is_building_function=False, enter_context_fn=eager_mode,
                device_stack=None)

  def push(self, is_building_function, enter_context_fn, device_stack):
    """Push metadata about a context switch onto the stack.

    A context switch can take any one of the two forms: installing a graph as
    the default graph, or entering the eager context. For each context switch,
    we record whether or not the entered context is building a function.

    Args:
      is_building_function: (bool.) Whether the context is building a function.
      enter_context_fn: (function.) A callable that executes the context switch.
        For example, `graph.as_default` or `eager_mode`.
      device_stack: If applicable, the device function stack for this
        graph. When breaking out of graphs in init_scope, the innermost nonempty
        device stack is used. Eager contexts put `None` here and the value is
        never used.
    """

    self.stack.append(
        ContextSwitch(is_building_function, enter_context_fn, device_stack))

  def pop(self):
    """Pop the stack."""

    self.stack.pop()


class LogicalDevice(