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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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package org.openjdk.bench.java.util.stream.ops.ref;

import org.openjdk.bench.java.util.stream.ops.LongAccumulator;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Param;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Warmup;

import java.util.concurrent.TimeUnit;
import java.util.function.Function;
import java.util.Arrays;
import java.util.stream.Stream;
import java.util.stream.Gatherer;
import static org.openjdk.bench.java.util.stream.ops.ref.BenchmarkGathererImpls.flatMap;

/**
 * Benchmark for map() operation implemented as Gatherer, with the default map implementation of Stream as baseline.
 */
@BenchmarkMode(Mode.Throughput)
@Warmup(iterations = 4, time = 5, timeUnit = TimeUnit.SECONDS)
@Measurement(iterations = 7, time = 5, timeUnit = TimeUnit.SECONDS)
@Fork(jvmArgsAppend = "--enable-preview", value = 1)
@OutputTimeUnit(TimeUnit.SECONDS)
@State(Scope.Thread)
public class GatherFlatMapInfinitySeq {

    /**
     * Implementation notes:
     *   - parallel version requires thread-safe sink, we use the same for sequential version for better comparison
     *   - operations are explicit inner classes to untangle unwanted lambda effects
     *   - the result of applying consecutive operations is the same, in order to have the same number of elements in sink
     */

    @Param({"10", "100", "1000"})
    private int size;

    private Function<Long, Stream<Long>> funInf;

    private Long[] cachedInputArray;

    private Gatherer<Long, ?, Long> gather_flatMap_inf;

    @Setup
    public void setup() {
        cachedInputArray = new Long[size];
        for(int i = 0;i < size;++i)
            cachedInputArray[i] = Long.valueOf(i);

        funInf = new Function<Long, Stream<Long>>() { @Override public Stream<Long> apply(Long l) {
            return Stream.generate(() -> l);
        } };

        gather_flatMap_inf = flatMap(funInf);
    }

    @Benchmark
    public long seq_invoke_baseline() {
        return Arrays.stream(cachedInputArray)
                .flatMap(funInf)
                .limit(size * 5)
                .collect(LongAccumulator::new, LongAccumulator::add, LongAccumulator::merge).get();
    }

    @Benchmark
    public long seq_invoke_gather() {
        return Arrays.stream(cachedInputArray)
                .gather(flatMap(funInf))
                .limit(size * 5)
                .collect(LongAccumulator::new, LongAccumulator::add, LongAccumulator::merge).get();
    }

    @Benchmark
    public long seq_invoke_gather_preallocated() {
        return Arrays.stream(cachedInputArray)
                .gather(gather_flatMap_inf)
                .limit(size * 5)
                .collect(LongAccumulator::new, LongAccumulator::add, LongAccumulator::merge).get();
    }
}
