Combiner.java

/* @file
 *****************************************************************************
 * @author     This file is part of zkspark, developed by SCIPR Lab
 *             and contributors (see AUTHORS).
 * @copyright  MIT license (see LICENSE file)
 *****************************************************************************/

package common;

import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.Function2;
import scala.Tuple2;

import java.util.ArrayList;

/**
 * Combiner implements a set of three functions used by JavaPairRDD.combineByKey() to partition
 * elements into the specified organization.
 */
public class Combiner<T> {

    // The following functions are used for combineByKey() in FFTAuxiliary, NaiveEvaluation, and BACE.
    public final Function<Tuple2<Long, T>, ArrayList<Tuple2<Long, T>>> createGroup = element -> {
        final ArrayList<Tuple2<Long, T>> a = new ArrayList<>();
        a.add(element);
        return a;
    };
    public final Function2<ArrayList<Tuple2<Long, T>>, Tuple2<Long, T>, ArrayList<Tuple2<Long, T>>>
            mergeElement = (element1, element2) -> {
        element1.add(element2);
        return element1;
    };
    public final Function2<ArrayList<Tuple2<Long, T>>, ArrayList<Tuple2<Long, T>>,
            ArrayList<Tuple2<Long, T>>> mergeCombiner = (element1, element2) -> {
        element1.addAll(element2);
        return element1;
    };

}