# -*- coding: utf-8 -*-
# This code is part of Qiskit.
#
# (C) Copyright IBM 2017, 2019.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""Check if the DAG has reached a fixed point."""
from copy import deepcopy
from qiskit.transpiler.basepasses import AnalysisPass
[docs]class DAGFixedPoint(AnalysisPass):
"""Check if the DAG has reached a fixed point.
A dummy analysis pass that checks if the DAG a fixed point (the DAG is not
modified anymore). The results is saved in
``property_set['dag_fixed_point']`` as a boolean.
"""
[docs] def run(self, dag):
"""Run the DAGFixedPoint pass on `dag`."""
if self.property_set['_dag_fixed_point_previous_dag'] is None:
self.property_set['dag_fixed_point'] = False
else:
fixed_point_reached = self.property_set['_dag_fixed_point_previous_dag'] == dag
self.property_set['dag_fixed_point'] = fixed_point_reached
self.property_set['_dag_fixed_point_previous_dag'] = deepcopy(dag)