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

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 * Licensed to the Apache Software Foundation (ASF) under one
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 * 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.MapFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.aggregation.Aggregations;
import org.apache.flink.api.java.operators.DeltaIteration;
import org.apache.flink.api.java.tuple.Tuple1;
import org.apache.flink.api.java.tuple.Tuple2;
import org.apache.flink.examples.java.graph.ConnectedComponents;
import org.apache.flink.test.testdata.ConnectedComponentsData;
import org.apache.flink.test.util.JavaProgramTestBase;

import java.io.BufferedReader;

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

    private static final long SEED = 0xBADC0FFEEBEEFL;

    private static final int NUM_VERTICES = 1000;

    private static final int NUM_EDGES = 10000;

    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 testProgram() throws Exception {
        // set up execution environment
        ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();

        // read vertex and edge data
        DataSet<Tuple1<Long>> vertices = env.readCsvFile(verticesPath).types(Long.class);

        DataSet<Tuple2<Long, Long>> edges =
                env.readCsvFile(edgesPath)
                        .fieldDelimiter(" ")
                        .types(Long.class, Long.class)
                        .flatMap(new ConnectedComponents.UndirectEdge());

        // assign the initial components (equal to the vertex id)
        DataSet<Tuple2<Long, Long>> verticesWithInitialId =
                vertices.map(new DuplicateValue<Long>());

        // open a delta iteration
        DeltaIteration<Tuple2<Long, Long>, Tuple2<Long, Long>> iteration =
                verticesWithInitialId.iterateDelta(verticesWithInitialId, 100, 0);

        // apply the step logic: join with the edges, select the minimum neighbor, update if the
        // component of the candidate is smaller
        DataSet<Tuple2<Long, Long>> changes =
                iteration
                        .getWorkset()
                        .join(edges)
                        .where(0)
                        .equalTo(0)
                        .with(new ConnectedComponents.NeighborWithComponentIDJoin())
                        .groupBy(0)
                        .aggregate(Aggregations.MIN, 1)
                        .join(iteration.getSolutionSet())
                        .where(0)
                        .equalTo(0)
                        .with(new ConnectedComponents.ComponentIdFilter());

        // close the delta iteration (delta and new workset are identical)
        DataSet<Tuple2<Long, Long>> result = iteration.closeWith(changes, changes);

        result.writeAsCsv(resultPath, "\n", " ");

        // execute program
        env.execute("Connected Components Example");
    }

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

    /**
     * Duplicate the vertex ID into both fields of a {@link Tuple2}.
     *
     * @param <T> key type
     */
    public static final class DuplicateValue<T> implements MapFunction<Tuple1<T>, Tuple2<T, T>> {

        @Override
        public Tuple2<T, T> map(Tuple1<T> vertex) {
            return new Tuple2<>(vertex.f0, vertex.f0);
        }
    }
}