// Copyright (c) Keith D Gregory, all rights reserved
package com.kdgregory.example.bytebuffer;

import java.nio.ByteBuffer;
import java.util.Random;


/**
 *  Compares the performance of in-heap and out-of-heap buffers, using
 *  random reads and writes.
 */
public class DirectSpeedTest
{
    public static void main(String[] argv)
    throws Exception
    {
        // source of randomness: replace the ctor param with a known
        // value if you want to ensure the same blocks are read/written
        // in the same order
        Random rnd = new Random(System.currentTimeMillis());

        // change "reps" to get a reasonable runtime on your system
        // change "writePct" to change the percentage of writes vs reads
        int size = 100 * 1024 * 1024;
        int reps = 100000000;

        // pick one of the following
        ByteBuffer buf = ByteBuffer.allocate(size);
        // ByteBuffer buf = ByteBuffer.allocateDirect(size);

        long start = System.currentTimeMillis();
        for (int ii = 0 ; ii < reps ; ii++)
        {
            int offset = rnd.nextInt(size - 4);
            buf.getInt(offset);
        }
        long finish = System.currentTimeMillis();
        long elapsed = finish - start;

        System.out.println(
                reps + " reps = "
                + elapsed + " milliseconds");
    }
}