def PowerGraph(graph: Graph[V,E],
    gatherf: Edge[V,E] => A,
    sumf: (A, A) => A,
    applyf: ((Id,V), A) => V,
    signalf: Edge[V,E]=> Bool,
    maxIter: Int): Graph[V,E] = {
    // Extend the vertex data to include isActive
    var glGraph = graph.mapVertices((Id,v) => (id, (true,v)))
    // Loop while there are active vertices
    var i = 0
    var nActive = g.numVertices
    while (i < maxIter && nActive > 0) {
        // Execute the gather phase
        val acc = glGraph.filterE(e => e.dst.isActive).aggregateNeighbors(gatherf, sumf)
        // Execute the apply phase.
        glGraph = glGraph.updateVertices(acc, applyf)
        // Execute the Scatter Phase
        val active = glGraph.filter(e=>e.src.isActive).aggregateNeighbors(scatterf, (a,b)=> a||b)
        // Update activity status of vertices
        glGraph = glGraph.updateVertices(active,
                    ((id, (old,v)), active)=>(id,(active,v)))
        // Count the number of active vertices
        nActive = glGraph.vertices.map(v => v.isActive).reduce((a,b) => a + b)
        i = i + 1
    }
    // Return the graph (without active flag)
    return glGraph.mapVertices(v => (v.id, v.data))
}