MAINT: random: Add assert() statements.

WarrenWeckesser · WarrenWeckesser · commit 1ded86d35efc · 2020-04-26T17:19:05.000-04:00
Assert that an invalid value (2**n-1 for n = 8, 16, 32, 64) has not
been passed to the Lemire function.
diff --git a/numpy/random/src/distributions/distributions.c b/numpy/random/src/distributions/distributions.c
@@ -6,6 +6,8 @@
 #include <intrin.h>
 #endif
 
+#include <assert.h>
+
 /* Inline generators for internal use */
 static NPY_INLINE uint32_t next_uint32(bitgen_t *bitgen_state) {
   return bitgen_state->next_uint32(bitgen_state->state);
@@ -1149,6 +1151,8 @@ static NPY_INLINE uint64_t bounded_lemire_uint64(bitgen_t *bitgen_state,
    */
   const uint64_t rng_excl = rng + 1;
 
+  assert(rng != 0xFFFFFFFFFFFFFFFFULL);
+
 #if __SIZEOF_INT128__
   /* 128-bit uint available (e.g. GCC/clang). `m` is the __uint128_t scaled
    * integer. */
@@ -1239,6 +1243,8 @@ static NPY_INLINE uint32_t buffered_bounded_lemire_uint32(
   uint64_t m;
   uint32_t leftover;
 
+  assert(rng != 0xFFFFFFFFUL);
+
   /* Generate a scaled random number. */
   m = ((uint64_t)next_uint32(bitgen_state)) * rng_excl;
 
@@ -1273,6 +1279,8 @@ static NPY_INLINE uint16_t buffered_bounded_lemire_uint16(
   uint32_t m;
   uint16_t leftover;
 
+  assert(rng != 0xFFFFU);
+
   /* Generate a scaled random number. */
   m = ((uint32_t)buffered_uint16(bitgen_state, bcnt, buf)) * rng_excl;
 
@@ -1308,6 +1316,9 @@ static NPY_INLINE uint8_t buffered_bounded_lemire_uint8(bitgen_t *bitgen_state,
   uint16_t m;
   uint8_t leftover;
 
+  assert(rng != 0xFFU);
+
+
   /* Generate a scaled random number. */
   m = ((uint16_t)buffered_uint8(bitgen_state, bcnt, buf)) * rng_excl;
 
