org.thejavaguy.prng.generators.R250 Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of rng Show documentation

Implementation of several (pseudo) random number generators which have better characteristics then Java's built in generator

There is a newer version: 0.2.0

Show newest version

package org.thejavaguy.prng.generators;

import java.util.Random;

/**
 * Generator of pseudo-random numbers based on GFSR(250,103) algorithm.
 * @author Ivan Milosavljevic (TheJavaGuy)
 */
public final class R250 implements PRNG {
    private static final int NUM_ELEMENTS = 250;
    private final int[] buffer;
    private int index;

    public R250() {
        this(System.nanoTime());
    }

    public R250(long seed) {
        buffer = new int[NUM_ELEMENTS];
        index = 0;
        Random randomGenerator = new Random(seed);
        for (int i = 0; i < buffer.length; ++i) {
            buffer[i] = randomGenerator.nextInt();
        }
        int msb = 0x80000000;
        int mask = 0xffffffff;
        for (int j = 0; j < 32; ++j) {
            int indexOfVector = 7 * j + 3;
            buffer[indexOfVector] &= mask;
            buffer[indexOfVector] |= msb;
            mask >>= 1;
        msb >>= 1;
        }
    }

    @Override
    public int nextInt() {
        int j = (index + 103) % NUM_ELEMENTS;
        int ret = buffer[index] ^ buffer[j];
        buffer[index] = ret;
        index = (index + 1) % NUM_ELEMENTS;
        return ret;
    }
}