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/*
* PURPOSE
* the basic rand generator of Scilab : s <- (a*s + c) mod m
* with :
* m = 2^{31}
* a = 843314861
* c = 453816693
*
* s must be in [0,m-1] when user changes seed with set_state_urand
* period = m
*
* NOTES
* a/ Rewritten (in C) so as to output integers like all the others
* generators (and also to have the same manner to set/get the state)
* b/ unsigned long int arithmetic must be the classic 32 bits unsigned
* arithmetic (ie also is exact modulo 2^32).
*
*/
#include "../graphics/Math.h" /* to use sciprint */
#include <math.h> /* to use floor */
static unsigned long s = 0;
unsigned long urandc()
{
s = 843314861ul * s + 453816693ul; /* => on obtient ici un resultat modulo 2^32 */
/* il suffit du test suivant pour obtenir le modulo 2^31 */
if (s >= 2147483648ul) s -= 2147483648ul;
return ( s );
}
int set_state_urand(double g)
{
if ( g == floor(g) && 0 <= g && g <= 2147483647 )
{
s = (unsigned long) g;
return ( 1 );
}
else
{
sciprint("\n\r bad seed for urand, must be an integer in [0, 2147483647]\n\r");
return ( 0 );
}
}
void get_state_urand(double g[])
{
g[0] = (double) s;
}
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