mirror of https://github.com/OpenTTD/OpenTTD.git
75 lines
2.1 KiB
C
75 lines
2.1 KiB
C
/* $Id$ */
|
|
|
|
#include "stdafx.h"
|
|
#include "openttd.h"
|
|
|
|
#ifdef MERSENNE_TWISTER
|
|
|
|
// Source code for Mersenne Twister.
|
|
// A Random number generator with much higher quality random numbers.
|
|
|
|
#define N (624) // length of _mt_state vector
|
|
#define M (397) // a period parameter
|
|
#define K (0x9908B0DFU) // a magic constant
|
|
#define hiBit(u) ((u) & 0x80000000U) // mask all but highest bit of u
|
|
#define loBit(u) ((u) & 0x00000001U) // mask all but lowest bit of u
|
|
#define loBits(u) ((u) & 0x7FFFFFFFU) // mask the highest bit of u
|
|
#define mixBits(u, v) (hiBit(u)|loBits(v)) // move hi bit of u to hi bit of v
|
|
|
|
static uint32 _mt_state[N+1]; // _mt_state vector + 1 extra to not violate ANSI C
|
|
static uint32 *_mt_next; // _mt_next random value is computed from here
|
|
static int _mt_left = -1; // can *_mt_next++ this many times before reloading
|
|
|
|
void SeedMT(uint32 seed)
|
|
{
|
|
register uint32 x = (seed | 1U) & 0xFFFFFFFFU, *s = _mt_state;
|
|
register int j;
|
|
|
|
for(_mt_left=0, *s++=x, j=N; --j;
|
|
*s++ = (x*=69069U) & 0xFFFFFFFFU);
|
|
}
|
|
|
|
|
|
static uint32 ReloadMT(void)
|
|
{
|
|
register uint32 *p0=_mt_state, *p2=_mt_state+2, *pM=_mt_state+M, s0, s1;
|
|
register int j;
|
|
|
|
if(_mt_left < -1)
|
|
SeedMT(4357U);
|
|
|
|
_mt_left=N-1, _mt_next=_mt_state+1;
|
|
|
|
for(s0=_mt_state[0], s1=_mt_state[1], j=N-M+1; --j; s0=s1, s1=*p2++)
|
|
*p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
|
|
|
|
for(pM=_mt_state, j=M; --j; s0=s1, s1=*p2++)
|
|
*p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
|
|
|
|
s1=_mt_state[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
|
|
s1 ^= (s1 >> 11);
|
|
s1 ^= (s1 << 7) & 0x9D2C5680U;
|
|
s1 ^= (s1 << 15) & 0xEFC60000U;
|
|
return(s1 ^ (s1 >> 18));
|
|
}
|
|
|
|
|
|
uint32 RandomMT(void)
|
|
{
|
|
uint32 y;
|
|
|
|
if(--_mt_left < 0)
|
|
return ReloadMT();
|
|
|
|
y = *_mt_next++;
|
|
y ^= (y >> 11);
|
|
y ^= (y << 7) & 0x9D2C5680U;
|
|
y ^= (y << 15) & 0xEFC60000U;
|
|
return y ^ (y >> 18);
|
|
}
|
|
#else
|
|
|
|
void SeedMT(uint32 seed) {}
|
|
|
|
#endif /* MERSENNE_TWISTER */
|