Source code for dimod.traversal

# The following traversal code is adapted from NetworkX's implementation. The
# only thing that was preventing their implementation from using BQMs directly
# was the not_implemented_for decorator. So rather than force the construction
# of a new NetworkX graph, we just skip that decorator (and make some other
# small changes). Modifications are licensed under the Apache 2.0 Software
# license at the top.
#
# Copyright 2019 D-Wave Systems Inc.
#
#    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.
#
# NetworkX license:
#
# Copyright (C) 2004-2019, NetworkX Developers
# Aric Hagberg <hagberg@lanl.gov>
# Dan Schult <dschult@colgate.edu>
# Pieter Swart <swart@lanl.gov>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#   * Redistributions of source code must retain the above copyright
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#     disclaimer in the documentation and/or other materials provided
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[docs]def connected_components(bqm): """Yields sets of connected variables. Args: bqm (:obj:`dimod.BinaryQuadraticModel`): A binary quadratic model (BQM). Yields: set: A set of variables in the BQM that form a connected component. """ seen = set() for v in bqm.variables: if v not in seen: c = set(bfs_variables(bqm, v)) yield c seen.update(c)
[docs]def bfs_variables(bqm, source): """Yields variables in breadth-first search order. Args: bqm (:obj:`dimod.BinaryQuadraticModel`): A binary quadratic model. source (variable): A variable in the binary quadratic model (BQM). Yields: variable: variables in the BQM, yielded in breadth-first search order starting at source. """ seen = set() nextlevel = {source} while nextlevel: thislevel = nextlevel nextlevel = set() for v in thislevel: if v not in seen: yield v seen.add(v) nextlevel.update(bqm.adj[v])