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[/] [or1k/] [trunk/] [uclinux/] [uC-libc/] [misc/] [rand.c] - Rev 199
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#ifdef ZX81_RNG /* * This is my favorite tiny RNG, If you had a ZX81 you may recognise it :-) * (RdeBath) */ #include <stdlib.h> #define MAXINT (((unsigned)-1)>>1) static unsigned int sseed = 0; int rand() { return ( sseed = (((sseed+1L)*75L)%65537L)-1 ) & MAXINT; } void srand(seed) unsigned int seed; { sseed=seed; } #else /* * This generator is a combination of three linear congruential generators * with periods or 2^15-405, 2^15-1041 and 2^15-1111. It has a period that * is the product of these three numbers. */ static int seed1 = 1; static int seed2 = 1; static int seed3 = 1; #define MAXINT (((unsigned)-1)>>1) #define CRANK(a,b,c,m,s) \ q = s/a; \ s = b*(s-a*q) - c*q; \ if(s<0) s+=m; int rand() { register int q, z; CRANK(206, 157, 31, 32363, seed1); CRANK(217, 146, 45, 31727, seed2); CRANK(222, 142, 133, 31657, seed3); return seed1^seed2^seed3; } void srand(seed) unsigned int seed; { seed &= MAXINT; seed1= seed%32362 + 1; seed2= seed%31726 + 1; seed3= seed%31656 + 1; } #endif
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