Source code for graphscope.analytical.app.is_simple_path

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright 2020 Alibaba Group Holding Limited. 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.
#
# Author: Ma JingYuan<nn9902@qq.com>
#

import json

from graphscope.framework.app import AppAssets
from graphscope.framework.app import not_compatible_for
from graphscope.framework.app import project_to_simple

__all__ = ["is_simple_path"]


@project_to_simple
@not_compatible_for("arrow_property")
def is_simple_path(graph, nodes):
    """Returns True if and only if `nodes` form a simple path in `G`.

    A *simple path* in a graph is a nonempty sequence of nodes in which
    no node appears more than once in the sequence, and each adjacent
    pair of nodes in the sequence is adjacent in the graph.

    Parameters
    ----------
    graph (:class:`graphscope.Graph`): A simple graph.
    nodes : list
        A list of one or more nodes in the graph `G`.

    Returns
    -------
    bool
        Whether the given list of nodes represents a simple path in `G`.

    Notes
    -----
    An empty list of nodes is not a path but a list of one node is a
    path. Here's an explanation why.

    This function operates on *node paths*. One could also consider
    *edge paths*. There is a bijection between node paths and edge
    paths.

    The *length of a path* is the number of edges in the path, so a list
    of nodes of length *n* corresponds to a path of length *n* - 1.
    Thus the smallest edge path would be a list of zero edges, the empty
    path. This corresponds to a list of one node.

    To convert between a node path and an edge path, you can use code
    like the following::

        >>> from networkx.utils import pairwise
        >>> nodes = [0, 1, 2, 3]
        >>> edges = list(pairwise(nodes))
        >>> edges
        [(0, 1), (1, 2), (2, 3)]
        >>> nodes = [edges[0][0]] + [v for u, v in edges]
        >>> nodes
        [0, 1, 2, 3]

    Examples
    --------
    .. code:: python

        >>> import graphscope
        >>> from graphscope.dataset import load_p2p_network
        >>> sess = graphscope.session(cluster_type="hosts", mode="eager")
        >>> g = load_p2p_network(sess)
        >>> # project to a simple graph (if needed)
        >>> pg = g.project(vertices={"host": ["id"]}, edges={"connect": ["dist"]})
        >>> c = graphscope.is_simple_path(pg, [2, 3, 8])
        >>> print(c)
        >>> sess.close()
    """
    if isinstance(nodes, list):
        n1json = json.dumps(nodes)
        ctx = AppAssets(algo="is_simple_path", context="tensor")(graph, n1json)
        return ctx.to_numpy("r", axis=0)[0]
    raise ValueError("input nodes is not a list object!")