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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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).
 *
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package org.openjdk.bench.java.util.stream.tasks.IntegerMax;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Level;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;

import java.util.Arrays;
import java.util.concurrent.RecursiveTask;
import java.util.concurrent.TimeUnit;
import java.util.function.BinaryOperator;

/**
 * Bulk scenario: search for max value in array.
 *
 * This test covers bulk infrastructure only. Refer to other tests for lambda-specific cases.
 */
@BenchmarkMode(Mode.Throughput)
@OutputTimeUnit(TimeUnit.SECONDS)
@State(Scope.Benchmark)
public class Bulk {

    private IntegerMaxProblem problem;

    @Setup(Level.Trial)
    public void populateData(){
        problem = new IntegerMaxProblem();
    }

    @Benchmark
    public int hm_seq() {
        int max = Integer.MIN_VALUE;
        for (int v: problem.get()) {
            if (v > max) {
                max = v;
            }
        }
        return max;
    }

    @Benchmark
    public int hm_par() {
        return new MaxIntTask(problem.get(), 0, problem.get().length).invoke();
    }

    @Benchmark
    public int bulk_seq_inner() {
        return Arrays.stream(problem.get()).reduce(Integer.MIN_VALUE, new BinaryOperator<Integer>() {
            @Override
            public Integer apply(Integer l, Integer r) {
                return l > r ? l : r;
            }
        });
    }

    @Benchmark
    public int bulk_par_inner() {
        return Arrays.stream(problem.get()).parallel().reduce(Integer.MIN_VALUE, new BinaryOperator<Integer>() {
            @Override
            public Integer apply(Integer l, Integer r) {
                return l > r ? l : r;
            }
        });
    }

    static class MaxIntTask extends RecursiveTask<Integer> {
        private static final int FORK_LIMIT = 1000;
        final Integer[] data;
        final int start, end;

        MaxIntTask(Integer[] data, int start, int end) {
            this.data = data;
            this.start = start;
            this.end = end;
        }

        @Override
        protected Integer compute() {
            int size = end - start;
            if (size > FORK_LIMIT) {
                int mid = start + size / 2;
                MaxIntTask t1 = new MaxIntTask(data, start, mid);
                MaxIntTask t2 = new MaxIntTask(data, mid, end);
                t1.fork();
                Integer v2 = t2.invoke();
                Integer v1 = t1.join();
                return Math.max(v1, v2);
            } else {
                int max = Integer.MIN_VALUE;
                for (int i = start; i < end; i++) {
                    if (data[i] > max) {
                        max = data[i];
                    }
                }
                return max;
            }
        }
    }

}