图间结构算子

Question

我们认为公共边=相同的srcId和相同的dstId，并且顶点和边是唯一的。

Answer 1

假设只有两个图，并且两个图都包含相同的顶点集，没有重复的边，您可以对一个新图使用组合边并使用groupedges方法：

val graph1: Graph[T,Double] = ???
val graph2: Graph[T,Double] = ???

Graph(graph1.vertices, graph1.edges.union(graph2.edges))
  .groupEdges((val1, val2) => (val1 + val2) / 2.0)

或者更普遍一点：

Graph(graph1.vertices, graph1.edges.union(graph2.edges))
  .mapEdges(e => (e.attr, 1.0))
  .groupEdges((val1, val2) => (val1._1 + val2._1, val1._2 + val2._2))
  .mapEdges(e => e.attr._1 / e.attr._2)

如果这还不够，您可以组合值并从头创建一个新的图：

def edgeToPair (e: Edge[Double]) = ((e.srcId, e.dstId), e.attr)
val pairs1 = graph1.edges.map(edgeToPair)
val pairs2 = graph2.edges.map(edgeToPair)

// Combine edges
val newEdges = pairs1.union(pairs2)
  .aggregateByKey((0.0, 0.0))(
    (acc, e) => (acc._1 + e, acc._2 + 1.0),
    (acc1, acc2) => (acc1._1 + acc2._1, acc1._2 + acc2._2)
  ).map{case ((srcId, dstId), (acc, count)) => Edge(srcId, dstId, acc / count)}

// Combine vertices assuming there are no conflicts
// like different labels
val newVertices = graph1.vertices.union(graph2.vertices).distinct

// Create new graph
val newGraph = Graph(newVertices, newEdges)