flink-tests/src/test/java/org/apache/flink/test/iterative/CoGroupConnectedComponentsITCase.java

/*
 * 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.test.iterative;

import org.apache.flink.api.common.functions.CoGroupFunction;
import org.apache.flink.api.common.functions.JoinFunction;
import org.apache.flink.api.common.functions.MapFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.functions.FunctionAnnotation.ForwardedFieldsFirst;
import org.apache.flink.api.java.functions.FunctionAnnotation.ForwardedFieldsSecond;
import org.apache.flink.api.java.operators.CoGroupOperator;
import org.apache.flink.api.java.operators.DeltaIteration;
import org.apache.flink.api.java.operators.JoinOperator;
import org.apache.flink.api.java.tuple.Tuple1;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.test.testdata.ConnectedComponentsData;
import org.apache.flink.test.util.JavaProgramTestBase;
import org.apache.flink.util.Collector;

import java.io.BufferedReader;
import java.util.Iterator;

/** Delta iteration test implementing the connected components algorithm with a cogroup. */
public class CoGroupConnectedComponentsITCase extends JavaProgramTestBase {

    private static final long SEED = 0xBADC0FFEEBEEFL;

    private static final int NUM_VERTICES = 1000;

    private static final int NUM_EDGES = 10000;

    private static final int MAX_ITERATIONS = 100;

    protected String verticesPath;
    protected String edgesPath;
    protected String resultPath;

    @Override
    protected void preSubmit() throws Exception {
        verticesPath =
                createTempFile(
                        "vertices.txt",
                        ConnectedComponentsData.getEnumeratingVertices(NUM_VERTICES));
        edgesPath =
                createTempFile(
                        "edges.txt",
                        ConnectedComponentsData.getRandomOddEvenEdges(
                                NUM_EDGES, NUM_VERTICES, SEED));
        resultPath = getTempFilePath("results");
    }

    @Override
    protected void postSubmit() throws Exception {
        for (BufferedReader reader : getResultReader(resultPath)) {
            ConnectedComponentsData.checkOddEvenResult(reader);
        }
    }

    // --------------------------------------------------------------------------------------------
    //  The test program
    // --------------------------------------------------------------------------------------------

    @Override
    protected void testProgram() throws Exception {

        ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

        DataSet<Tuple1<Long>> initialVertices =
                env.readCsvFile(verticesPath)
                        .fieldDelimiter(" ")
                        .types(Long.class)
                        .name("Vertices");

        DataSet<Tuple2<Long, Long>> edges =
                env.readCsvFile(edgesPath)
                        .fieldDelimiter(" ")
                        .types(Long.class, Long.class)
                        .name("Edges");

        DataSet<Tuple2<Long, Long>> verticesWithId =
                initialVertices
                        .map(
                                new MapFunction<Tuple1<Long>, Tuple2<Long, Long>>() {
                                    @Override
                                    public Tuple2<Long, Long> map(Tuple1<Long> value)
                                            throws Exception {
                                        return new Tuple2<>(value.f0, value.f0);
                                    }
                                })
                        .name("Assign Vertex Ids");

        DeltaIteration<Tuple2<Long, Long>, Tuple2<Long, Long>> iteration =
                verticesWithId.iterateDelta(verticesWithId, MAX_ITERATIONS, 0);

        JoinOperator<Tuple2<Long, Long>, Tuple2<Long, Long>, Tuple2<Long, Long>> joinWithNeighbors =
                iteration
                        .getWorkset()
                        .join(edges)
                        .where(0)
                        .equalTo(0)
                        .with(
                                new JoinFunction<
                                        Tuple2<Long, Long>,
                                        Tuple2<Long, Long>,
                                        Tuple2<Long, Long>>() {
                                    @Override
                                    public Tuple2<Long, Long> join(
                                            Tuple2<Long, Long> first, Tuple2<Long, Long> second)
                                            throws Exception {
                                        return new Tuple2<>(second.f1, first.f1);
                                    }
                                })
                        .name("Join Candidate Id With Neighbor");

        CoGroupOperator<Tuple2<Long, Long>, Tuple2<Long, Long>, Tuple2<Long, Long>> minAndUpdate =
                joinWithNeighbors
                        .coGroup(iteration.getSolutionSet())
                        .where(0)
                        .equalTo(0)
                        .with(new MinIdAndUpdate())
                        .name("min Id and Update");

        iteration
                .closeWith(minAndUpdate, minAndUpdate)
                .writeAsCsv(resultPath, "\n", " ")
                .name("Result");

        env.execute("Workset Connected Components");
    }

    @ForwardedFieldsFirst("f1->f1")
    @ForwardedFieldsSecond("f0->f0")
    private static final class MinIdAndUpdate
            implements CoGroupFunction<Tuple2<Long, Long>, Tuple2<Long, Long>, Tuple2<Long, Long>> {
        private static final long serialVersionUID = 1L;

        @Override
        public void coGroup(
                Iterable<Tuple2<Long, Long>> first,
                Iterable<Tuple2<Long, Long>> second,
                Collector<Tuple2<Long, Long>> out)
                throws Exception {
            Iterator<Tuple2<Long, Long>> current = second.iterator();
            if (!current.hasNext()) {
                throw new Exception("Error: Id not encountered before.");
            }
            Tuple2<Long, Long> old = current.next();
            long oldId = old.f1;

            long minimumComponentID = Long.MAX_VALUE;

            for (Tuple2<Long, Long> candidate : first) {
                long candidateComponentID = candidate.f1;
                if (candidateComponentID < minimumComponentID) {
                    minimumComponentID = candidateComponentID;
                }
            }

            if (minimumComponentID < oldId) {
                out.collect(new Tuple2<>(old.f0, minimumComponentID));
            }
        }
    }
}