/*
 * 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
 * limitations under the License.
 */
package org.apache.logging.log4j.perf.jmh;

import java.util.concurrent.TimeUnit;

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

/**
 * From <a href="http://shipilev.net/blog/2014/nanotrusting-nanotime/">http://shipilev.net/blog/2014/nanotrusting-nanotime/</a>.
 */
// ============================== HOW TO RUN THIS TEST: ====================================
//
// single thread:
// java -jar log4j-perf/target/benchmarks.jar ".*Nanotime.*" -f 1 -wi 5 -i 5
//
// multiple threads (for example, 4 threads):
// java -jar log4j-perf/target/benchmarks.jar ".*Nanotime.*" -f 1 -wi 5 -i 5 -t 4 -si true
//
// Usage help:
// java -jar log4j-perf/target/benchmarks.jar -help
//
@State(Scope.Benchmark)
public class NanotimeBenchmark {

    public static void main(final String[] args) {
    }

    @Benchmark
    @BenchmarkMode(Mode.SampleTime)
    @OutputTimeUnit(TimeUnit.NANOSECONDS)
    public void baseline() {
    }

    @Benchmark
    @BenchmarkMode(Mode.SampleTime)
    @OutputTimeUnit(TimeUnit.NANOSECONDS)
    public long latency_nanotime() {
        return System.nanoTime();
    }

    private long lastValue;

    @Benchmark
    @BenchmarkMode(Mode.SampleTime)
    @OutputTimeUnit(TimeUnit.NANOSECONDS)
    public long granularity_nanotime() {
        long cur;
        do {
            cur = System.nanoTime();
        } while (cur == lastValue);
        lastValue = cur;
        return cur;
    }
}
