diff options
| author | ludde <ludde@openttd.org> | 2005-07-15 20:29:06 +0000 |
|---|---|---|
| committer | ludde <ludde@openttd.org> | 2005-07-15 20:29:06 +0000 |
| commit | fd0cee74182900b6cdcf679e0fbdd16f0cf59466 (patch) | |
| tree | 4082dbe36cd4d476e1d16f70a88eaa90adb7523f /mersenne.c | |
| parent | ac4f823b547f77781dc6738882a3da601a17dc9b (diff) | |
| download | openttd-fd0cee74182900b6cdcf679e0fbdd16f0cf59466.tar.xz | |
(svn r2583) Move OS specific code out of misc.c
Added support for Mersenne Twister random number generator (not implemented in network yet)
Wrap player randoms around #ifdef
Diffstat (limited to 'mersenne.c')
| -rw-r--r-- | mersenne.c | 72 |
1 files changed, 72 insertions, 0 deletions
diff --git a/mersenne.c b/mersenne.c new file mode 100644 index 000000000..98170084f --- /dev/null +++ b/mersenne.c @@ -0,0 +1,72 @@ +#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
\ No newline at end of file |