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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [stdlib/] [rand_r.c] - Rev 307
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#include <stdlib.h> /* Pseudo-random generator based on Minimal Standard by Lewis, Goodman, and Miller in 1969. I[j+1] = a*I[j] (mod m) where a = 16807 m = 2147483647 Using Schrage's algorithm, a*I[j] (mod m) can be rewritten as: a*(I[j] mod q) - r*{I[j]/q} if >= 0 a*(I[j] mod q) - r*{I[j]/q} + m otherwise where: {} denotes integer division q = {m/a} = 127773 r = m (mod a) = 2836 note that the seed value of 0 cannot be used in the calculation as it results in 0 itself */ int _DEFUN (rand_r, (seed), unsigned int *seed) { long k; long s = (long)(*seed); if (s == 0) s = 0x12345987; k = s / 127773; s = 16807 * (s - k * 127773) - 2836 * k; if (s < 0) s += 2147483647; (*seed) = (unsigned int)s; return (int)(s & RAND_MAX); }
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