python 图形工具访问顶点属性

Question

对于我当前的项目，我想使用图形工具库，因为它们声称是最快的：https://graph-tool.skewed.de/performance。我有一些算法（最短路径等）可以在非常大的网络上运行，所以越快越好！

第一个问题：这个说法 'being the fastest' 是真的吗？ ;)

在尝试构建适合我需要的图形工具图形时，我发现无法以有效的方式访问顶点属性。也许我错过了什么？

我现在的问题是，函数 "getVertexFromGraph(graph, position)" 可以用更有效的方式编写吗？或者更笼统地说：我能否有效地检查一个顶点（由其位置属性给出）是否已经在图中。

提前致谢！

import graph_tool as gt
#from graph_tool.all import *

edgeList = [[(0.5,1),(2.1,4.3)],[(2.1,4.3),(5.4,3.3)],[(5.4,3.3),(1.3,3.5)],[(4.4,3.3),(2.3,3.5)]] #A lot more coordinate values....

# Initialize the graph
routableNetwork = gt.Graph()

# Initialize the vertex property "position" to store the vertex coordinates
vpPosition = routableNetwork.new_vertex_property("vector<double>")
routableNetwork.vertex_properties["position"] = vpPosition

def getVertexFromGraph(graph, position):
    """
    This method checks if a vertex, identified by its position, is in the given graph or not.
    :param graph:       The graph containing all vertices to check  
    :param position:    The vertex/position to check
    :return:            The ID of the vertex if the vertex is already in the graph, 'None' otherwise
    """
    for v in graph.vertices():
        if graph.vp.position[v] == position:
            return v
    return None

def main():
    """
    This method creates the graph by looping over all given edges, inserting every: 
        - non existent vertex in the graph with its coordinates (property 'position')  
        - edge with its corresponding length (property 'distance')
    :return: -
    """
    for e in edgeList:
        vertex0 = getVertexFromGraph(routableNetwork,e[0])
        vertex1 = getVertexFromGraph(routableNetwork,e[1])
        if vertex0 == None:
            vertex0 = routableNetwork.add_vertex()
            routableNetwork.vertex_properties['position'][vertex0] = e[0]
        if vertex1 == None:
            vertex1 = routableNetwork.add_vertex()
            routableNetwork.vertex_properties['position'][vertex1] = e[1]

        edge = routableNetwork.add_edge(vertex0,vertex1)
        #routableNetwork.edge_properties['distance'][edge] = calculateDistance(e[0][0],e[0][1],e[1][0],e[1][1])

    #saveRoutableNetwork(routableNetwork)
    #graph_draw(routableNetwork, vertex_text=routableNetwork.vertex_index, vertex_font_size=18, output_size=(200, 200), output="two-nodes.png")

if __name__ == "__main__":
    main()

Answer 1

您要找的函数是find_vertex():

https://graph-tool.skewed.de/static/doc/util.html#graph_tool.util.find_vertex

重要的是要认识到 graph-tool 通过将对性能敏感的循环从 Python 卸载到 C++ 来实现其速度。因此，每当您像在代码中那样遍历顶点时，就会失去任何优势。

另请注意，尽管 find_vertex() 是用 C++ 实现的，因此比纯 Python 中的等效项快很多倍，但它仍然是一个 O(N) 操作。对于大图，最好创建一个很好的旧 python 字典，将属性值映射到顶点，它的查找成本为 O(1)。

python 图形工具访问顶点属性

python graph-tool access vertex properties

python

graph-algorithm

networkx

graph-tool