Redline/source/random.cpp

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//random.cpp
//random number generator
#include <stdlib.h>
#include <time.h>
#include <math.h>
/* A C-program for TT800 : July 8th 1996 Version */
/* by M. Matsumoto, email: matumoto@math.keio.ac.jp */
/* genrand() generate one pseudorandom number with double precision */
/* which is uniformly distributed on [0,1]-interval */
/* for each call. One may choose any initial 25 seeds */
/* except all zeros. */
/* See: ACM Transactions on Modelling and Computer Simulation, */
/* Vol. 4, No. 3, 1994, pages 254-266. */
#define N 25
#define M 7
unsigned long x[N]; /* initial 25 seeds, change as you wish */
double genrand()
{
unsigned long y;
static int k = 0;
static unsigned long mag01[2]={
0x0, 0x8ebfd028 /* this is magic vector `a', don't change */
};
if (k==N) { /* generate N words at one time */
int kk;
for (kk=0;kk<N-M;kk++) {
x[kk] = x[kk+M] ^ (x[kk] >> 1) ^ mag01[x[kk] % 2];
}
for (; kk<N;kk++) {
x[kk] = x[kk+(M-N)] ^ (x[kk] >> 1) ^ mag01[x[kk] % 2];
}
k=0;
}
y = x[k];
y ^= (y << 7) & 0x2b5b2500; /* s and b, magic vectors */
y ^= (y << 15) & 0xdb8b0000; /* t and c, magic vectors */
y &= 0xffffffff; /* you may delete this line if word size = 32 */
/*
the following line was added by Makoto Matsumoto in the 1996 version
to improve lower bit's corellation.
Delete this line to o use the code published in 1994.
*/
y ^= (y >> 16); /* added to the 1994 version */
k++;
return( (double) y / (unsigned long) 0xffffffff);
}
//APIs to use genrand function
void RandomInit()
//Inits the random seeds using the standard C rand() function
{
int i;
time_t t;
time(&t);
srand(t);
for(i=0;i<N;i++)
x[i]=rand();
}
float RandomFl(float min,float max)
//gives a random float evenly distibuted in the intervall [min,max]
{
return genrand()*(max-min)+min;
}
int RandomInt(int min,int max)
//gives a random int evenly distributed in the intervall [min,max-1]
{
double ran;
do ran=genrand(); while(ran==1);
return floor(ran*(max-min)+min);
}
int RandomProb(float prob)
//returns true with a probility of prob
//(ie. if prob is 1 always returns true, if prob is 0 always returns false)
{
return genrand()<=prob;
}