def generateRandomUndirectedGraph()

in cassovary-core/src/main/scala/com/twitter/cassovary/graph/TestGraph.scala [289:323]
25 lines of code
4 McCabe index (conditional complexity)

  def generateRandomUndirectedGraph(numNodes: Int, probEdge: Double,
                                    graphDir: StoredGraphDir = StoredGraphDir.BothInOut,
                                    rand: Random = new Random,
                                    parallelismLimit: Int = 2) = {

    val futurePool = new BoundedFuturePool(FuturePool.unboundedPool, parallelismLimit)

    val nodes = Array.fill(numNodes){new ConcurrentLinkedQueue[Int]()}
    def addMutualEdge(i: Int)(j: Int) {nodes(i).add(j); nodes(j).add(i)}
    val binomialDistribution = new BinomialDistribution(numNodes - 1, probEdge)
    // Sampling edges only from nodes with lower id to higher id. In order to
    // reuse the same binomial distribution we match nodes in pairs, so that
    // one with id 0 is matched with one with id (n - 1), id 1 is matched with (n - 2)
    // and so on. Observe, that there is (n - 1) potential edges for every pair, that
    // connect from lower id node to higher. Thus for each pair we need to sample a vector
    // of Bernoulli variables of size (n - 1), from which we interprete first (lowerNode - 1)
    // bits as edges from higherNode and the rest from the node with lower id.
    val futures = (0 to (numNodes - 1) / 2) map {
      lowerNode => futurePool {
        val higherNode = numNodes - 1 - lowerNode
        val (higherNodeNeighbors, lowerNodeNeighbors) = randomSubset(binomialDistribution,
          0 until numNodes - 1, rand) partition (_ < lowerNode)
        lowerNodeNeighbors.map(_ + 1) foreach addMutualEdge(lowerNode)
        if (lowerNode != higherNode)
          higherNodeNeighbors map (higherNode + _ + 1) foreach addMutualEdge(higherNode)
      }
    }
    Await.ready(Future.join(futures))

    val nodesEdges = nodes.indices map { i =>
      NodeIdEdgesMaxId(i, nodes(i).asScala.toArray)
    }
    ArrayBasedDirectedGraph(nodesEdges, graphDir,
      NeighborsSortingStrategy.LeaveUnsorted)
  }