zipf/pareto: ensure that 0 isn't always the hottest block

[fio.git] / lib / zipf.c

diff --git a/lib/zipf.c b/lib/zipf.c
index 527ae294cf9afd6212151e004e2220163e25f888..8cd25864792ba185320077a9e7619ef2a3360d35 100644 (file)
--- a/lib/zipf.c
+++ b/lib/zipf.c
@@ -88,20 +88,26 @@ punt:
        zs->nranges = f.nranges;
 }
 
+static void shared_rand_init(struct zipf_state *zs, unsigned long nranges)
+{
+       memset(zs, 0, sizeof(*zs));
+       zs->nranges = nranges;
+
+       init_rand(&zs->rand);
+       zs->rand_off = __rand(&zs->rand);
+}
+
 void zipf_init(struct zipf_state *zs, unsigned long nranges, double theta)
 {
        unsigned int i;
 
-       memset(zs, 0, sizeof(*zs));
+       shared_rand_init(zs, nranges);
 
-       zs->nranges = nranges;
        zs->theta = theta;
 
        for (i = 1; i <= 2; i++)
                zs->zeta2 += pow(1.0 / (double) i, zs->theta);
 
-       init_rand(&zs->rand);
-
        zipf_load_gen_zeta(zs);
 }
 
@@ -125,17 +131,13 @@ unsigned long long zipf_next(struct zipf_state *zs)
        else
                val = 1 + (unsigned long long)(n * pow(eta*rand_uni - eta + 1.0, alpha));
 
-       return __hash_long(val - 1) % zs->nranges;
+       return (__hash_long(val - 1) + zs->rand_off) % zs->nranges;
 }
 
 void pareto_init(struct zipf_state *zs, unsigned long nranges, double h)
 {
-       memset(zs, 0, sizeof(*zs));
-
-       zs->nranges = nranges;
+       shared_rand_init(zs, nranges);
        zs->pareto_pow = log(h) / log(1.0 - h);
-
-       init_rand(&zs->rand);
 }
 
 unsigned long long pareto_next(struct zipf_state *zs)
@@ -143,5 +145,5 @@ unsigned long long pareto_next(struct zipf_state *zs)
        double rand = (double) __rand(&zs->rand) / (double) FRAND_MAX;
        unsigned long long n = zs->nranges - 1;
 
-       return __hash_long(n * pow(rand, zs->pareto_pow)) % zs->nranges;
+       return (__hash_long(n * pow(rand, zs->pareto_pow)) + zs->rand_off) % zs->nranges;
 }