musl/src/prng/rand.c

#include <stdlib.h>
#include <stdint.h>

static uint64_t seed;

void srand(unsigned s)
{
	seed = s-1;
}

int rand(void)
{
	seed = 6364136223846793005ULL*seed + 1;
	return seed>>33;
}
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`#include <stdlib.h>`
prng: fix rand() to give good sequence with small state some applications rely on the low bits of rand() to be reasonably good quality prng, so now it fixed by using the top bits of a 64 bit LCG, this is simple, has small state and passes statistical tests. D.E. Knuth attributes the multiplier to C.E. Haynes in TAOCP Vol2 3.3.4 2013-06-08 13:31:10 +00:00			`#include <stdint.h>`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00
prng: fix rand() to give good sequence with small state some applications rely on the low bits of rand() to be reasonably good quality prng, so now it fixed by using the top bits of a 64 bit LCG, this is simple, has small state and passes statistical tests. D.E. Knuth attributes the multiplier to C.E. Haynes in TAOCP Vol2 3.3.4 2013-06-08 13:31:10 +00:00			`static uint64_t seed;`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00
			`void srand(unsigned s)`
			`{`
			`seed = s-1;`
			`}`

			`int rand(void)`
			`{`
prng: fix rand() to give good sequence with small state some applications rely on the low bits of rand() to be reasonably good quality prng, so now it fixed by using the top bits of a 64 bit LCG, this is simple, has small state and passes statistical tests. D.E. Knuth attributes the multiplier to C.E. Haynes in TAOCP Vol2 3.3.4 2013-06-08 13:31:10 +00:00			`seed = 6364136223846793005ULL*seed + 1;`
			`return seed>>33;`
initial check-in, version 0.5.0 2011-02-12 00:22:29 -05:00			`}`