0ad/source/dcdt/se/sr_random.cpp

#include "precompiled.h"
#include "0ad_warning_disable.h"
# include "sr.h"
# include "sr_random.h"

//========================= static methods =============================================

/* From: http://www.math.keio.ac.jp/~matumoto/mt19937int.c        */
/*  genrand() generates one pseudorandom unsigned integer (32bit) */
/* which is uniformly distributed among 0 to 2^32-1  for each     */
/* call. sgenrand(seed) set initial values to the working area    */
/* of 624 words. Before genrand(), sgenrand(seed) must be         */
/* called once. (seed is any 32-bit integer except for 0).        */
/*   Coded by Takuji Nishimura, considering the suggestions by    */
/* Topher Cooper and Marc Rieffel in July-Aug. 1997.              */

/* This library is free software; you can redistribute it and/or   */
/* modify it under the terms of the GNU Library General Public     */
/* License as published by the Free Software Foundation; either    */
/* version 2 of the License, or (at your option) any later         */
/* version.                                                        */
/* This library is distributed in the hope that it will be useful, */
/* but WITHOUT ANY WARRANTY; without even the implied warranty of  */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.            */
/* See the GNU Library General Public License for more details.    */
/* You should have received a copy of the GNU Library General      */
/* Public License along with this library; if not, write to the    */
/* Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA   */ 
/* 02111-1307  USA                                                 */

/* Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura.       */
/* Any feedback is very welcome. For any question, comments,       */
/* see http://www.math.keio.ac.jp/matumoto/emt.html or email       */
/* matumoto@math.keio.ac.jp                                        */

/* Period parameters */  
#define N 624
#define M 397
#define MATRIX_A 0x9908b0df   /* constant vector a */
#define UPPER_MASK 0x80000000 /* most significant w-r bits */
#define LOWER_MASK 0x7fffffff /* least significant r bits */

/* Tempering parameters */   
#define TEMPERING_MASK_B 0x9d2c5680
#define TEMPERING_MASK_C 0xefc60000
#define TEMPERING_SHIFT_U(y)  (y >> 11)
#define TEMPERING_SHIFT_S(y)  (y << 7)
#define TEMPERING_SHIFT_T(y)  (y << 15)
#define TEMPERING_SHIFT_L(y)  (y >> 18)

static unsigned long mt[N]; /* the array for the state vector  */
static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */
static bool first_use=true;

/* initializing the array with a NONZERO seed */
static void sgenrand ( unsigned long seed )
{
    /* setting initial seeds to mt[N] using         */
    /* the generator Line 25 of Table 1 in          */
    /* [KNUTH 1981, The Art of Computer Programming */
    /*    Vol. 2 (2nd Ed.), pp102]                  */
    mt[0]= seed & 0xffffffff;
    for (mti=1; mti<N; mti++)
        mt[mti] = (69069 * mt[mti-1]) & 0xffffffff;
}

static unsigned long genrand()
{
    unsigned long y;
    static unsigned long mag01[2]={0x0, MATRIX_A};
    /* mag01[x] = x * MATRIX_A  for x=0,1 */

    if (mti >= N) { /* generate N words at one time */
        int kk;

        if (mti == N+1)   /* if sgenrand() has not been called, */
            sgenrand(4357); /* a default initial seed is used   */

        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 & 0x1];
        }
        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 & 0x1];
        }
        y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
        mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];

        mti = 0;
    }
  
    y = mt[mti++];
    y ^= TEMPERING_SHIFT_U(y);
    y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
    y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
    y ^= TEMPERING_SHIFT_L(y);

    return y; 
}

static double drand () // between 0 and 1
 {
   static double max = double(0xffffffff);
   double r = double(genrand());
   return r / max;
 }

//========================= SrRandom =============================================

SrRandom::SrRandom ()
 {
   if ( first_use ) { sgenrand(1); first_use=false; }
   limits ( 0.0f, 1.0f );
 }

void SrRandom::limits ( double inf, double sup )
 {
   _inf = inf;
   _sup = sup;
   _dif = sup-inf;
   _type = 'd';
 }

void SrRandom::limits ( float inf, float sup, int br )
 {
   _inf = (double)inf;
   _sup = (double)sup;
   _dif = _sup-_inf;
   _type = 'f';
 }

void SrRandom::limits ( int inf, int sup )
 {
   _inf = (double)inf;
   _sup = (double)sup;
   _dif = (double)(sup-inf);
   _type = 'i';
 }

int SrRandom::geti ()
 {
   double r = drand()*_dif;
   return int ( _inf + SR_ROUND(r) );
 }

float SrRandom::getf ()
 {
   return float ( _inf + drand()*_dif );
 }

double SrRandom::getd ()
 {
   unsigned long a=genrand()>>5, b=genrand()>>6;
   // this gives a uniform randomnumber in [0,1) with 53-bit precision:
   double d = (a*67108864.0+b)*(1.0/9007199254740992.0);
   return _inf + d * _dif;
 }

//=== Static Methods =======================================================================

void SrRandom::seed ( unsigned long seed )
 {
   if ( first_use ) first_use=false;
   sgenrand ( seed );
 }

float SrRandom::randf ()
 {
   if ( first_use ) { sgenrand(1); first_use=false; }
   return (float) drand();
 }

//=== End of File =======================================================================