/* This is a maximally equidistributed combined Tausworthe generator based on code from GNU Scientific Library 1.5 (30 Jun 2004) x_n = (s1_n ^ s2_n ^ s3_n) s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19)) s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25)) s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11)) The period of this generator is about 2^88. From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe Generators", Mathematics of Computation, 65, 213 (1996), 203--213. This is available on the net from L'Ecuyer's home page, http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps There is an erratum in the paper "Tables of Maximally Equidistributed Combined LFSR Generators", Mathematics of Computation, 68, 225 (1999), 261--269: http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps ... the k_j most significant bits of z_j must be non- zero, for each j. (Note: this restriction also applies to the computer code given in [4], but was mistakenly not mentioned in that paper.) This affects the seeding procedure by imposing the requirement s1 > 1, s2 > 7, s3 > 15. */ #include "rand.h" #include "../hash.h" struct frand_state __fio_rand_state; static inline int __seed(unsigned int x, unsigned int m) { return (x < m) ? x + m : x; } void init_rand(struct frand_state *state) { #define LCG(x) ((x) * 69069) /* super-duper LCG */ state->s1 = __seed(LCG((2^31) + (2^17) + (2^7)), 1); state->s2 = __seed(LCG(state->s1), 7); state->s3 = __seed(LCG(state->s2), 15); __rand(state); __rand(state); __rand(state); __rand(state); __rand(state); __rand(state); } void fill_random_buf(void *buf, unsigned int len) { unsigned long r = __rand(&__fio_rand_state); long *ptr = buf; if (sizeof(int) != sizeof(*ptr)) r *= (unsigned long) __rand(&__fio_rand_state); while ((void *) ptr - buf < len) { *ptr = r; ptr++; r *= GOLDEN_RATIO_PRIME; r >>= 3; } }