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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
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package org.openjdk.bench.java.lang.stable;

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.OperationsPerInvocation;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.Threads;
import org.openjdk.jmh.annotations.Warmup;

import java.util.List;
import java.util.concurrent.TimeUnit;
import java.util.function.IntFunction;

/**
 * Benchmark measuring stable list performance
 */
@BenchmarkMode(Mode.AverageTime)
@OutputTimeUnit(TimeUnit.NANOSECONDS)
@State(Scope.Benchmark) // Share the same state instance (for contention)
@Warmup(iterations = 5, time = 1)
@Measurement(iterations = 5, time = 2)
@Fork(value = 2, jvmArgsAppend = {
        "--enable-preview"
})
@Threads(Threads.MAX)   // Benchmark under contention
@OperationsPerInvocation(100)
public class StableListBenchmark {

    private static final int SIZE = 100;
    private static final IntFunction<Integer> IDENTITY = i -> i;

    private static final List<Integer> LIST = List.ofLazy(SIZE, IDENTITY);
    private static final IntFunction<Integer> INT_FUNCTION = LIST::get;

    private final List<Integer> list = List.ofLazy(SIZE, IDENTITY);
    private final IntFunction<Integer> intFunction = list::get;

    @Benchmark
    public int list() {
        int sum = 0;
        for (int i = 0; i < SIZE; i++) {
            sum += list.get(i);
        }
        return sum;
    }

    @Benchmark
    public int intFunction() {
        int sum = 0;
        for (int i = 0; i < SIZE; i++) {
            sum += intFunction.apply(i);
        }
        return sum;
    }

    @Benchmark
    public int staticList() {
        int sum = 0;
        for (int i = 0; i < SIZE; i++) {
            sum += LIST.get(i);
        }
        return sum;
    }

    @Benchmark
    public int staticIntFunction() {
        int sum = 0;
        for (int i = 0; i < SIZE; i++) {
            sum += INT_FUNCTION.apply(i);
        }
        return sum;
    }

}
