Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1211#discussion_r41411193
--- Diff:
flink-staging/flink-gelly-scala/src/main/scala/org/apache/flink/graph/scala/example/SingleSourceShortestPaths.scala
---
@@ -0,0 +1,170 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you 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.
+ */
+
+package org.apache.flink.graph.scala.example;
+
+import org.apache.flink.api.scala._
+import org.apache.flink.graph.scala._
+import org.apache.flink.types.NullValue
+import org.apache.flink.graph.Edge
+import org.apache.flink.api.common.functions.MapFunction
+import org.apache.flink.graph.spargel.VertexUpdateFunction
+import org.apache.flink.graph.spargel.MessageIterator
+import org.apache.flink.graph.Vertex
+import org.apache.flink.graph.spargel.MessagingFunction
+import scala.collection.JavaConversions._
+import org.apache.flink.graph.scala.utils.Tuple3ToEdgeMap
+import org.apache.flink.graph.example.utils.SingleSourceShortestPathsData
+
+/**
+ * This example shows how to use Gelly's vertex-centric iterations.
+ *
+ * It is an implementation of the Single-Source-Shortest-Paths algorithm.
+ *
+ * The input file is a plain text file and must be formatted as follows:
+ * Edges are represented by tuples of srcVertexId, trgVertexId, distance
which are
+ * separated by tabs. Edges themselves are separated by newlines.
+ * For example: <code>1\t2\t0.1\n1\t3\t1.4\n</code> defines two edges,
+ * edge 1-2 with distance 0.1, and edge 1-3 with distance 1.4.
+ *
+ * If no parameters are provided, the program is run with default data from
+ * [[org.apache.flink.graph.example.utils.SingleSourceShortestPathsData]]
+ */
+object SingleSourceShortestPaths {
+ def main(args: Array[String]) {
+ if (!parseParameters(args)) {
+ return
+ }
+
+ val env = ExecutionEnvironment.getExecutionEnvironment
+ val edges: DataSet[Edge[Long, Double]] = getEdgesDataSet(env)
+ val graph = Graph.fromDataSet[Long, Double, Double](edges, new
InitVertices(srcVertexId), env)
+
+ // Execute the vertex-centric iteration
+ val result = graph.runVertexCentricIteration(new VertexDistanceUpdater,
+ new MinDistanceMessenger, maxIterations)
+
+ // Extract the vertices as the result
+ val singleSourceShortestPaths = result.getVertices
+
+ // emit result
+ if (fileOutput) {
+ singleSourceShortestPaths.writeAsCsv(outputPath, "\n", ",")
+ env.execute("Single Source Shortest Paths Example")
+ } else {
+ singleSourceShortestPaths.print()
+ }
+ }
+
+ //
--------------------------------------------------------------------------------------------
+ // Single Source Shortest Path UDFs
+ //
--------------------------------------------------------------------------------------------
+
+ private final class InitVertices(srcId: Long) extends MapFunction[Long,
Double] {
+
+ override def map(id: Long) = {
+ if (id.equals(srcId)) {
+ 0.0
+ } else {
+ Double.PositiveInfinity
+ }
+ }
+ }
+
+ /**
+ * Function that updates the value of a vertex by picking the minimum
+ * distance from all incoming messages.
+ */
+ private final class VertexDistanceUpdater extends
VertexUpdateFunction[Long, Double, Double] {
+
+ override def updateVertex(vertex: Vertex[Long, Double], inMessages:
MessageIterator[Double]) {
+ var minDistance = Double.MaxValue
+ while (inMessages.hasNext) {
+ var msg = inMessages.next
+ if (msg < minDistance) {
+ minDistance = msg
+ }
+ }
+ if (vertex.getValue > minDistance) {
+ setNewVertexValue(minDistance)
+ }
+ }
+ }
+
+ /**
+ * Distributes the minimum distance associated with a given vertex among
all
+ * the target vertices summed up with the edge's value.
+ */
+ private final class MinDistanceMessenger extends
+ MessagingFunction[Long, Double, Double, Double] {
+
+ override def sendMessages(vertex: Vertex[Long, Double]) {
+ for (edge: Edge[Long, Double] <- getEdges) {
+ sendMessageTo(edge.getTarget(), vertex.getValue + edge.getValue)
+ }
+ }
+ }
+
+ //
****************************************************************************
+ // UTIL METHODS
+ //
****************************************************************************
+
+ private var fileOutput = false
+ private var srcVertexId = 1L
+ private var edgesInputPath: String = null
+ private var outputPath: String = null
+ private var maxIterations = 5
+
+ private def parseParameters(args: Array[String]): Boolean = {
+ if(args.length > 0) {
+ if(args.length != 4) {
+ System.err.println("Usage: SingleSourceShortestPaths <source
vertex id>" +
+ " <input edges path> <output path> <num iterations>")
+ false
+ }
+ fileOutput = true
--- End diff --
indention +2 spaces?
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