Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/1211#discussion_r41410709
--- Diff:
flink-staging/flink-gelly-scala/src/main/scala/org/apache/flink/graph/scala/example/GSASingleSourceShortestPaths.scala
---
@@ -0,0 +1,156 @@
+/*
+ * 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 scala.collection.JavaConversions._
+import org.apache.flink.graph.scala.utils.Tuple3ToEdgeMap
+import org.apache.flink.graph.example.utils.SingleSourceShortestPathsData
+import org.apache.flink.graph.gsa.GatherFunction
+import org.apache.flink.graph.gsa.Neighbor
+import org.apache.flink.graph.gsa.SumFunction
+import org.apache.flink.graph.gsa.ApplyFunction
+
+/**
+ * This example shows how to use Gelly's gather-sum-apply 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 GSASingleSourceShortestPaths {
+ 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 gather-sum-apply iteration
+ val result = graph.runGatherSumApplyIteration(new CalculateDistances,
new ChooseMinDistance,
+ new UpdateDistance, maxIterations)
+
+ // Extract the vertices as the result
+ val singleSourceShortestPaths = result.getVertices
+
+ // emit result
+ if (fileOutput) {
+ singleSourceShortestPaths.writeAsCsv(outputPath, "\n", ",")
+ env.execute("GSA 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
+ }
+ }
+ }
+
+ private final class CalculateDistances extends GatherFunction[Double,
Double, Double] {
+ override def gather(neighbor: Neighbor[Double, Double]) = {
+ neighbor.getNeighborValue + neighbor.getEdgeValue
+ }
+ }
+
+ private final class ChooseMinDistance extends SumFunction[Double,
Double, Double] {
+ override def sum(newValue: Double, currentValue: Double) = {
+ Math.min(newValue, currentValue)
+ }
+ }
+
+ private final class UpdateDistance extends ApplyFunction[Long, Double,
Double] {
+ override def apply(newDistance: Double, oldDistance: Double) = {
+ if (newDistance < oldDistance) {
+ setResult(newDistance)
+ }
+ }
+ }
+
+ //
**************************************************************************
+ // 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
+ srcVertexId = args(0).toLong
+ edgesInputPath = args(1)
+ outputPath = args(2)
+ maxIterations = (3).toInt
+ } else {
+ System.out.println("Executing Single Source Shortest Paths example
"
+ + "with default parameters and built-in default data.")
+ System.out.println(" Provide parameters to read input data from
files.")
+ System.out.println(" See the documentation for the correct format
of input files.")
+ System.out.println("Usage: SingleSourceShortestPaths <source
vertex id>" +
+ " <input edges path> <output path> <num iterations>");
+ }
+ true
+ }
+
+ private def getEdgesDataSet(env: ExecutionEnvironment):
DataSet[Edge[Long, Double]] = {
+ if (fileOutput) {
+ env.readCsvFile[(Long, Long, Double)](edgesInputPath,
+ lineDelimiter = "\n",
+ fieldDelimiter = "\t")
+ .map(new Tuple3ToEdgeMap[Long, Double]())
+ } else {
--- End diff --
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