我正在尝试在Python中使用C中创建完全相同的 Mersenne Twister(MT).
基于Lib/random.py以及阅读文档,似乎整个MT _random实现在C中实现:
The underlying implementation in C is both fast and threadsafe.
通过谷歌搜索"Python _random",我在GitHub上找到了这个页面,这似乎正是我想要的,虽然它似乎不是正式的.
我使用了这个源代码并删除了除MT本身,种子函数和双重创建函数之外的所有内容.我还改变了一些类型,使整数为32位.
首先,这是许可证信息(只是为了安全)
/* Random objects */
/* ------------------------------------------------------------------
The code in this module was based on a download from:
http://www.math.keio.ac.jp/~matumoto/MT2002/emt19937ar.html
It was modified in 2002 by Raymond Hettinger as follows:
* the principal computational lines untouched.
* renamed genrand_res53() to random_random() and wrapped
in python calling/return code.
* genrand_int32() and the helper functions, init_genrand()
and init_by_array(), were declared static, wrapped in
Python calling/return code. also, their global data
references were replaced with structure references.
* unused functions from the original were deleted.
new, original C python code was added to implement the
Random() interface.
The following are the verbatim comments from the original code:
A C-program for MT19937, with initialization improved 2002/1/26.
Coded by Takuji Nishimura and Makoto Matsumoto.
Before using, initialize the state by using init_genrand(seed)
or init_by_array(init_key, key_length).
Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. The names of its contributors may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Any feedback is very welcome.
http://www.math.keio.ac.jp/matumoto/emt.html
email: matumoto@math.keio.ac.jp
*/
/* ---------------------------------------------------------------*/
这是剥离的头文件(删除了所有Python).
mt.h:
#ifndef MT_H
#define MT_H
#include <stdint.h>
#define N 624
#define M 397
#define MATRIX_A 0x9908b0dfUL /* constant vector a */
#define UPPER_MASK 0x80000000UL /* most significant w-r bits */
#define LOWER_MASK 0x7fffffffUL /* least significant r bits */
typedef struct {
uint32_t state[N];
uint32_t index;
} RandomObject;
static uint32_t
genrand_int32(RandomObject *self)
{
uint32_t y;
static uint32_t mag01[2]={0x0UL, MATRIX_A};
/* mag01[x] = x * MATRIX_A for x=0,1 */
uint32_t *mt;
mt = self->state;
if (self->index >= N) { /* generate N words at one time */
uint32_t kk;
for (kk=0;kk<N-M;kk++) {
y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
}
for (;kk<N-1;kk++) {
y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
}
y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];
self->index = 0;
}
y = mt[self->index++];
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return y;
}
static double
random_random(RandomObject *self)
{
uint32_t a=genrand_int32(self)>>5, b=genrand_int32(self)>>6;
return (double)((a*67108864.0+b)*(1.0/9007199254740992.0));
}
static void
init_genrand(RandomObject *self, uint32_t s)
{
uint32_t mti;
uint32_t *mt;
mt = self->state;
mt[0]= s & 0xffffffffUL;
for (mti=1; mti<N; mti++) {
mt[mti] =
(1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti);
/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
/* In the previous versions, MSBs of the seed affect */
/* only MSBs of the array mt[]. */
/* 2002/01/09 modified by Makoto Matsumoto */
mt[mti] &= 0xffffffffUL;
/* for >32 bit machines */
}
self->index = mti;
return;
}
#endif
这里有一个主要功能,只需创建一个MT对象,播种它,然后吐出一个随机的双.
main.c
#include <stdio.h>
#include "mt.h"
int main() {
RandomObject rand;
init_genrand(&rand, 0x1234);
printf("%lf\n", random_random(&rand));
return 0;
}
输出是:0.279194.
我的想法是,当我在python中执行相同的过程时,我得出相同的随机数:
Python 2.7.12 (default, Jul 1 2016, 15:12:24)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import random
>>> random.seed(0x1234)
>>> random.random()
0.9281175899596723
当然,输出是不同的(或者我不会在这里问).
我的问题是:我的手术有什么问题？我只是使用错误的来源？我是否对Python从C返回的值做了什么有缺陷的假设？
老实说我对Python知之甚少,所以我可能会在某个地方犯一个愚蠢的错误.
您缺少的是，它random.seed()不会调用init_genrand()种子初始状态，而是使用init_by_array()它（这是因为在Python中，整数可以是任意大小，并且我们希望将种子的所有位捕获到状态中）。
RandomObject rand;
uint32_t key[] = {0x1234};
init_by_array(&rand, key, sizeof(key)/sizeof(*key)); // <--
printf("%f\n", random_random(&rand));