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rand.c sollte man besser einfügen

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Yamagi Burmeister 2010-06-17 14:35:21 +00:00
parent 06099868fb
commit 9447523700
1 changed files with 91 additions and 0 deletions
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src/common/rand.c Normal file
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/* PRNG based on Mersenne Twister (M. Matsumoto and T. Nishimura, 1998). */
#include "qcommon.h"
#define RAND_M 397
#define RAND_N 624
#define MASK_U 0x80000000U
#define MASK_L 0x7fffffffU
#define MASK32 0xffffffffU
rand_work_t rand_work;
void
ini_rand ( unsigned int u )
{
int i;
rand_work.count = RAND_N;
rand_work.cnst [ 0 ] = 0;
rand_work.cnst [ 1 ] = 0x9908b0dfU;
u &= MASK32;
rand_work.vec [ 0 ] = u;
for ( i = 1; i < RAND_N; i++ )
{
u = i + 1812433253U * ( u ^ ( u >> 30 ) );
u &= MASK32;
rand_work.vec [ i ] = u;
}
}
int
mtrand ( void )
{
int u, u0, u1, u2;
int i;
if ( rand_work.count == RAND_N )
{
rand_work.count = 0;
for ( i = 0; i < RAND_N - RAND_M; i++ )
{
u = rand_work.vec [ i ] & MASK_U;
u |= rand_work.vec [ i + 1 ] & MASK_L;
u0 = rand_work.vec [ i + RAND_M ];
u1 = u >> 1;
u2 = rand_work.cnst [ u & 1 ];
rand_work.vec [ i ] = u0 ^ u1 ^ u2;
}
for ( ; i < RAND_N - 1; i++ )
{
u = rand_work.vec [ i ] & MASK_U;
u |= rand_work.vec [ i + 1 ] & MASK_L;
u0 = rand_work.vec [ i + RAND_M - RAND_N ];
u1 = u >> 1;
u2 = rand_work.cnst [ u & 1 ];
rand_work.vec [ i ] = u0 ^ u1 ^ u2;
}
u = rand_work.vec [ RAND_N - 1 ] & MASK_U;
u |= rand_work.vec [ 0 ] & MASK_L;
u0 = rand_work.vec [ RAND_M - 1 ];
u1 = u >> 1;
u2 = rand_work.cnst [ u & 1 ];
rand_work.vec [ RAND_N - 1 ] = u0 ^ u1 ^ u2;
}
u = rand_work.vec [ rand_work.count++ ];
u ^= ( u >> 11 );
u ^= ( u << 7 ) & 0x9d2c5680U;
u ^= ( u << 15 ) & 0xefc60000U;
u ^= ( u >> 18 );
if ( u < 0)
{
return ( ( u * -1 ) / 3 );
}
else
{
return ( u / 3 );
}
}