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Last active August 29, 2015 14:03
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MT19937 with improved initialization, optimization, and simplification.
/*
MT19937 with initialization improved 2002/2/10.
Coded by Takuji Nishimura and Makoto Matsumoto.
Faster version using Shawn Cokus's optimization and
Matthe Bellew's simplification.
Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
3. The names of its contributors may not be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/MT2002/emt19937ar.html
Modifications to original: Hardcoded period parameters. Implemented minimal
stdint. Removed initialization by array. Removed initialization check. Removed
real versions. Stripped comments and general formatting cleanup. Made state
variables into a struct. Renamed functions to be more consistent. Changed
next_state to use state's counter variable. Inlined next_state inside genrand.
Removed next pointer, only using state counter. Added macro for random doubles
in range [0-1]. Modified TWIST macro for minor speedup. Strict ANSI C.
*/
#ifndef __MTARCOK_H
#define __MTARCOK_H
/* minimal stdint implementation */
typedef signed short int16_t;
typedef unsigned long uint32_t;
/* state struct */
typedef struct {
uint32_t s[624];
int16_t i;
} mtstate_t;
/* global state object */
static mtstate_t mt = {{0}, 624};
/* initialize state with single seed. MUST be called before use */
void mt_init( uint32_t s ) {
int16_t j;
mt.s[0] = s & 0xffffffffUL;
for ( j = 1; j < 624; j++ ) {
mt.s[j] = (1812433253UL * (mt.s[j - 1] ^ (mt.s[j - 1] >> 30)) + j);
mt.s[j] &= 0xffffffffUL;
}
mt.i = 624;
}
#define TWIST( u, v ) ((((u & 0x80000000UL) | (v & 0x7fffffffUL)) >> 1) ^ ((v & 1UL) * 0x9908b0dfUL))
/* random unsigned 32bit integer */
uint32_t mt_rand( void ) {
uint32_t y;
/* generate the next state if needed */
if ( mt.i == 624 ) {
uint32_t* p = mt.s;
for ( mt.i = 228; --mt.i; p++ )
*p = p[397] ^ TWIST( p[0], p[1] );
for ( mt.i = 397; --mt.i; p++ )
*p = p[-227] ^ TWIST( p[0], p[1] );
*p = p[-227] ^ TWIST( p[0], p[0] );
mt.i = 0;
}
y = mt.s[mt.i++];
y ^= (y >> 11);
y ^= (y << 7) & 0x9d2c5680UL;
y ^= (y << 15) & 0xefc60000UL;
y ^= (y >> 18);
return y;
}
/* random double [0-1] */
#define mt_random() (mt_rand() * (1.0 / 0xffffffffUL))
#endif /* __MTARCOK_H */
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