diff options
author | KUDr <KUDr@openttd.org> | 2007-01-10 18:12:09 +0000 |
---|---|---|
committer | KUDr <KUDr@openttd.org> | 2007-01-10 18:12:09 +0000 |
commit | 07c30785ab226c4762b442f5a09ec745017cc94b (patch) | |
tree | d9abc3d9810159441bed9f82a52bd1ee52d770dd /src/mersenne.cpp | |
parent | dc44d341075a525d6069bfbf935efe75ac7ff0f0 (diff) | |
download | openttd-07c30785ab226c4762b442f5a09ec745017cc94b.tar.xz |
(svn r8033) [cpp] - Prepare for merge from branches/cpp (all .c files renamed to .cpp)
Diffstat (limited to 'src/mersenne.cpp')
-rw-r--r-- | src/mersenne.cpp | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/src/mersenne.cpp b/src/mersenne.cpp new file mode 100644 index 000000000..bc4cb949a --- /dev/null +++ b/src/mersenne.cpp @@ -0,0 +1,74 @@ +/* $Id$ */ + +#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 */ |