Added proper fallback for stc64_uniform

1 files changed, 11 insertions, 4 deletions

diff --git a/include/stc/crandom.h b/include/stc/crandom.h
index 38ab6b4b..eef4b6a4 100644
--- a/include/stc/crandom.h
+++ b/include/stc/crandom.h
@@ -118,13 +118,20 @@ STC_INLINE double stc64_uniformf(stc64_t* rng, stc64_uniformf_t* dist) {
 }

 

 /* Unbiased bounded uniform distribution. */

-#ifdef c_umul128

 STC_INLINE int64_t stc64_uniform(stc64_t* rng, stc64_uniform_t* d) {

+#ifdef c_umul128

     uint64_t lo, hi;

     do { c_umul128(stc64_rand(rng), d->range, &lo, &hi); } while (lo < d->threshold);

     return d->lower + hi;

-}

+#else

+    uint64_t x, r;

+    do {

+        x = stc64_rand(rng);

+        r = x % d->range;

+    } while (x - r > -d->range);

+    return d->lower + r;

 #endif

+}

 

 STC_INLINE int32_t stc32_uniform(stc32_t* rng, stc32_uniform_t* d) {

     uint64_t val;

@@ -165,14 +172,14 @@ STC_DEF stc32_t stc32_with_seq(uint32_t seed, uint32_t seq) {
     for (int i = 0; i < 6; ++i) stc32_rand(&rng);

     return rng;

 }

-#ifdef c_umul128

+

 /* Init unbiased uniform uint RNG with bounds [low, high] */

 STC_DEF stc64_uniform_t stc64_uniform_init(int64_t low, int64_t high) {

     stc64_uniform_t dist = {low, (uint64_t) (high - low + 1)};

     dist.threshold = (uint64_t)(-dist.range) % dist.range;

     return dist;

 }

-#endif

+

 STC_DEF stc32_uniform_t stc32_uniform_init(int32_t low, int32_t high) {

     stc32_uniform_t dist = {low, (uint32_t) (high - low + 1)};

     dist.threshold = (uint32_t)(-dist.range) % dist.range;