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A framework for writing performance micro-benchmarks using JUnit4 annotations, forked from https://github.com/carrotsearch/junit-benchmarks.

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package com.carrotsearch.junitbenchmarks;

import java.lang.management.ManagementFactory;
import java.lang.management.ThreadMXBean;

/**
 * Used to specify what time to measure in {@link BenchmarkOptions}.
 */
public enum Clock
{

    /**
     * Invokes {@link System#currentTimeMillis()}
     */
    REAL_TIME
            {
                @Override
                long time()
                {
                    return System.currentTimeMillis();
                }
            },

    /**
     * Invokes {@link System#nanoTime()}
     */
    NANO_TIME
            {
                @Override
                long time()
                {
                    return System.nanoTime() / FACTOR;
                }
            },

    /**
     * Invokes {@link java.lang.management.ThreadMXBean#getCurrentThreadCpuTime()}
     */
    CPU_TIME
            {
                @Override
                long time()
                {
                    if (mxBean.isThreadCpuTimeSupported())
                    {
                        return mxBean.getCurrentThreadCpuTime() / FACTOR;
                    } else
                    {
                        throw new RuntimeException("ThreadCpuTime is not supported. Impossible to use Clock.CPU_TIME");
                    }
                }
            },
    /**
     * Invokes {@link java.lang.management.ThreadMXBean#getCurrentThreadUserTime()}
     */
    USER_TIME
            {
                @Override
                long time()
                {
                    if (mxBean.isThreadCpuTimeSupported())
                    {
                        return mxBean.getCurrentThreadUserTime() / FACTOR;
                    } else
                    {
                        throw new RuntimeException("ThreadCpuTime is not supported. Impossible to use Clock.USER_TIME");
                    }
                }
            };

    private static final int FACTOR = 1000000;
    private static ThreadMXBean mxBean;

    static
    {
        mxBean = ManagementFactory.getThreadMXBean();
        if (mxBean.isThreadCpuTimeSupported()) mxBean.setThreadCpuTimeEnabled(true);
    }

    abstract long time();
}