Python `random.random() işlevindeki işlevselliği C

Question

Python'da kullanılan C içinde tam aynı Mersenne Twister (MT) oluşturmaya çalışıyorum. Ben gibi görünüyor this page on GitHub bulduk, "Python _random" googling tarafından

The underlying implementation in C is both fast and threadsafe. 

: the docs okuma yanı sıra Lib/random.py dayanarak

, C uygulanan _random uygulanan tüm MT gibi görünüyor resmi olarak görünmese de tam olarak aradığım şey.

Bu kaynak kodunu kullandım ve MT'nin kendisi, tohum işlevi ve çift oluşturma işlevi dışındaki her şeyi yok ettim. Ayrıca bazı türleri değiştirdim, böylece tamsayılar 32 bit olacaktı.

Öncelikle burada

İşte

/* 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 
*/ 

/* ---------------------------------------------------------------*/ 

(çıkarılmış herşey Python ile) aşağıya soyulmuş başlık dosyasıdır (sadece güvenli olması için) lisans bilgisi olduğunu.

mt.h

: Burada

#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 

Ve sadece MT nesnesi yaratan bir ana işlevi, tohumlar öyle ve sonra rasgele bir çift tükürür.

main.c

#include <stdio.h> 
#include "mt.h" 

int main() { 
    RandomObject rand; 
    init_genrand(&rand, 0x1234); 
    printf("%lf\n", random_random(&rand)); 
    return 0; 
} 

çıktısı: 0.279194.

fikri Python eşdeğer süreci ne zaman, ben aynı rasgele sayıyı çıkmak, yani:

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 

çıktı, tabii ki, (ya da ben farklı burada soran olmaz edilir).

Sorum şu: Bu prosedürde sorun nedir? Yanlış kaynağı mı kullanıyorum? Python'un C'den geri dönen değerlerle ne yaptığı konusunda kusurlu varsayımlar mı yapıyorum?

Python hakkında çok fazla şey bilmiyorum, bu yüzden bir yerlerde aptalca bir hata yapabilirim. Eğer eksik ne

Answer 1

random.seed() başlangıç ​​durumunu, but use init_by_array() instead tohuma init_genrand() çağrı olmamasıdır (Python bir tamsayı büyüklüğünde keyfi olabilir çünkü bu, ve biz duruma tohumun tüm bit yakalamak istiyorsunuz).

RandomObject rand; 
uint32_t key[] = {0x1234}; 
init_by_array(&rand, key, sizeof(key)/sizeof(*key)); // <-- 
printf("%f\n", random_random(&rand));