rand: add 64-bit tausworthe variant with a 2^258 cycle

[fio.git] / lib / rand.c

diff --git a/lib/rand.c b/lib/rand.c
index 1d189a277cca2e9fa0c6c5d32cd9a70b41f867a2..2e4c66e144b5cc56a04ec8c4747e435368b68a3a 100644 (file)
--- a/lib/rand.c
+++ b/lib/rand.c
@@ -40,12 +40,12 @@
 
 int arch_random;
 
-static inline int __seed(unsigned int x, unsigned int m)
+static inline uint64_t __seed(uint64_t x, uint64_t m)
 {
        return (x < m) ? x + m : x;
 }
 
-static void __init_rand(struct frand_state *state, unsigned int seed)
+static void __init_rand32(struct taus88_state *state, unsigned int seed)
 {
        int cranks = 6;
 
@@ -56,17 +56,43 @@ static void __init_rand(struct frand_state *state, unsigned int seed)
        state->s3 = __seed(LCG(state->s2, seed), 15);
 
        while (cranks--)
-               __rand(state);
+               __rand32(state);
 }
 
-void init_rand(struct frand_state *state)
+static void __init_rand64(struct taus258_state *state, uint64_t seed)
 {
-       __init_rand(state, 1);
+       int cranks = 6;
+
+#define LCG64(x, seed)  ((x) * 6906969069ULL ^ (seed))
+
+       state->s1 = __seed(LCG64((2^31) + (2^17) + (2^7), seed), 1);
+       state->s2 = __seed(LCG64(state->s1, seed), 7);
+       state->s3 = __seed(LCG64(state->s2, seed), 15);
+       state->s4 = __seed(LCG64(state->s3, seed), 33);
+       state->s5 = __seed(LCG64(state->s4, seed), 49);
+
+       while (cranks--)
+               __rand64(state);
 }
 
-void init_rand_seed(struct frand_state *state, unsigned int seed)
+void init_rand(struct frand_state *state, int use64)
 {
-       __init_rand(state, seed);
+       state->use64 = use64;
+
+       if (!use64)
+               __init_rand32(&state->state32, 1);
+       else
+               __init_rand64(&state->state64, 1);
+}
+
+void init_rand_seed(struct frand_state *state, unsigned int seed, int use64)
+{
+       state->use64 = use64;
+
+       if (!use64)
+               __init_rand32(&state->state32, seed);
+       else
+               __init_rand64(&state->state64, seed);
 }
 
 void __fill_random_buf(void *buf, unsigned int len, unsigned long seed)