学步园

梅森旋转随机算法，C++和Java代码。

C++：

#ifndef _MersenneTwister_H_
#define _MersenneTwister_H_

#include <time.h>
#include <stdint.h>
#include <math.h>

typedef int32_t MS_INT;

class MersenneTwister
{
public:
	void rseed(MS_INT seed){
		if(isInitialized){
			return ;
		}
		msInit(seed);
	}
	int rand(void){
		if(isInitialized == false){
			return 0;
		}
		return msRand();
	}
public:
	MersenneTwister(int seed):isInitialized(0){
		rseed(seed);
	}
	~MersenneTwister(){

	}
	/* Initialize the generator from a seed */
	void msInit(int seed) {
		MS_INT i;
		MS_INT p;
		idx = 0;
		MT[0] = seed;
		for (i=1; i < 624; ++i) { /* loop over each other element */
			p = 1812433253 * (MT[i-1] ^ (MT[i-1] >> 30)) + i;
			MT[i] = p & 0xffffffff; /* get last 32 bits of p */
		}
		isInitialized = 1;
	}

	/* Extract a tempered pseudorandom number based on the idx-th value,
	calling ms_generate() every 624 numbers */
	MS_INT msRand() { 
		if (!isInitialized)
			msInit((MS_INT)time(NULL)); 

		if (idx == 0)
			msGenerate();

		MS_INT y = MT[idx];
		y = y ^ (y >> 11);
		y = y ^ ((y << 7) & 2636928640);
		y = y ^ ((y << 15) & 4022730752);
		y = y ^ (y >> 18);

		idx = (idx + 1) % 624; /* increment idx mod 624*/
		return y;
	}

	/* Generate an array of 624 untempered numbers */
	void msGenerate() {
		MS_INT i, y;
		for (i = 0; i < 624; ++i) {
			y = (MT[i] & 0x80000000) + 
				(MT[(i+1) % 624] & 0x7fffffff);
			MT[i] = MT[(i + 397) % 624] ^ (y >> 1);
			if (y % 2) { /* y is odd */
				MT[i] = MT[i] ^ (2567483615);
			}
		}
	} 
private:
	MS_INT MT[624];
	MS_INT idx;
	MS_INT isInitialized;
};

#endif

Java：

package com.art.util;

public class MersenneTwister {
	/* Create a length 624 array to store the state of the generator */
	private int [] MT = new int[624];
	private int idx;
	private boolean isInitialized = false;

	/* Initialize the generator from a seed */
	private void msInit(int seed) {
		int i;
		int p;
	    idx = 0;
	    MT[0] = seed;
	    for (i=1; i < 624; ++i) { /* loop over each other element */
	        p = 1812433253 * (MT[i-1] ^ (MT[i-1] >> 30)) + i;
	        MT[i] = p & 0xffffffff; /* get last 32 bits of p */
	    }
	    isInitialized = true;
	}
	
	private int msRand() {
	    if (!isInitialized){
	    	return 0;
	    }
	    	

	    if (idx == 0)
	        msRenerate();

	    int y = MT[idx];
	    y = y ^ (y >> 11);
	    y = y ^ ((y << 7) & (int)2636928640l);
	    y = y ^ ((y << 15) & (int)4022730752l);
	    y = y ^ (y >> 18);

	    idx = (idx + 1) % 624; /* increment idx mod 624*/
	    return y;
	}
	 
	private void msRenerate() {
	    int i;
	    int y;
	    for (i = 0; i < 624; ++i) {
	        y = (MT[i] & 0x80000000) + 
	                (MT[(i+1) % 624] & 0x7fffffff);
	        MT[i] = MT[(i + 397) % 624] ^ (y >> 1);
	        if (y % 2 != 0) { /* y is odd */
	            MT[i] = MT[i] ^ (int)(2567483615l);
	        }
	    }
	}
	
	//随机种子
	public void rseed(int seed){
		if(isInitialized){
			return ;
		}
		msInit(seed);
	}
	
	//随机值
	public int rand(){
		if(isInitialized == false){
			return 0;
		}
		return msRand();
	}
	
	public MersenneTwister(int seed){
		rseed(seed);
	}

}