flink-tests/src/test/java/org/apache/flink/test/iterative/IterationWithAllReducerITCase.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
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 */

package org.apache.flink.test.iterative;

import org.apache.flink.api.common.functions.ReduceFunction;
import org.apache.flink.api.java.DataSet;
import org.apache.flink.api.java.ExecutionEnvironment;
import org.apache.flink.api.java.operators.IterativeDataSet;
import org.apache.flink.test.util.JavaProgramTestBase;

import java.util.List;

/** Test iterator with an all-reduce. */
public class IterationWithAllReducerITCase extends JavaProgramTestBase {
    private static final String EXPECTED = "1\n";

    @Override
    protected void testProgram() throws Exception {
        ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
        env.setParallelism(4);

        DataSet<String> initialInput = env.fromElements("1", "1", "1", "1", "1", "1", "1", "1");

        IterativeDataSet<String> iteration = initialInput.iterate(5).name("Loop");

        DataSet<String> sumReduce =
                iteration
                        .reduce(
                                new ReduceFunction<String>() {
                                    @Override
                                    public String reduce(String value1, String value2)
                                            throws Exception {
                                        return value1;
                                    }
                                })
                        .name("Compute sum (Reduce)");

        List<String> result = iteration.closeWith(sumReduce).collect();

        compareResultAsText(result, EXPECTED);
    }
}