X-Git-Url: http://git.draconx.ca/gitweb/cdecl99.git/blobdiff_plain/1c3b0c0e6f9339e76e42f6393e554c7dfc58e205..HEAD:/t/rng.c

diff --git a/t/rng.c b/t/rng.c
index 8ae2f13..63e0818 100644
--- a/t/rng.c
+++ b/t/rng.c
@@ -1,6 +1,6 @@
 /*
  * Simple random number generator for testing.
- * Copyright © 2022 Nick Bowler
+ * Copyright © 2022-2024 Nick Bowler
  *
  * This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -15,24 +15,25 @@
  * You should have received a copy of the GNU General Public License
  * along with this program.  If not, see <https://www.gnu.org/licenses/>.
  *
- * The RNG implementation is adapted from xoshiro256+ and splitmix64
- * by David Blackman and Sebastiano Vigna, originally distributed under
- * the Creative Commons Zero public domain dedication.
+ * The RNG implementation is adapted from xoshiro256+ by David Blackman
+ * and Sebastiano Vigna, originally distributed under the Creative Commons
+ * Zero public domain dedication.
  */
 
 #include <config.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <inttypes.h>
 #include <errno.h>
 #include <limits.h>
-#include <float.h>
-#include <math.h>
+#include <inttypes.h>
 
-#include "test.h"
+#if !TEST_RNG_NO_EXTERNAL_API
+#  include "test.h"
+#endif
 
-#define B64(x) ((x) & 0xffffffffffffffff)
+#define B64(x) ((x) & 0xffffffffffffffffull)
+#define B32(x) ((x) & 0xffffffffu)
 
 struct test_rng {
 	unsigned long long state[4];
@@ -61,52 +62,51 @@ static unsigned long long xoshiro256p(unsigned long long *s)
 	return ret;
 }
 
-static unsigned long long splitmix64(unsigned long long *state)
+/*
+ * 32-bit random number generator for seed expansion.
+ *
+ * The output filter is from the public domain MurmurHash3 by Austin Appleby.
+ *
+ * The state is incremented by the fractional part of the golden ratio,
+ * i.e., floor( (sqrt(5)-1)/2 * 2**32 )
+ */
+static uint_least32_t splitmix32(uint_least32_t *state)
 {
-	unsigned long long z;
+	uint_least32_t z;
 
-	z = B64(*state += 0x9e3779b97f4a7c15);
-	z = B64((z ^ (z >> 30)) * 0xbf58476d1ce4e5b9);
-	z = B64((z ^ (z >> 27)) * 0x94d049bb133111eb);
+	z = B32(*state += 0x9e3779b9);
+	z = B32((z ^ (z >> 16)) * 0x85ebca6b);
+	z = B32((z ^ (z >> 13)) * 0xc2b2ae35);
 
-	return z ^ (z >> 31);
+	return z ^ (z >> 16);
 }
 
-#if HAVE_STRTOULL
-#  define STRTOULL strtoull
-#elif HAVE___STRTOULL
-/* HP-UX 11 has __strtoull in <inttypes.h> */
-#  define STRTOULL __strtoull
-#else
-/*
- * Just fall back to strtoul -- in the worst case we just lose the ability
- * to set all 64 bits of the seed.
- */
-#  define STRTOULL strtoul
-#endif
+static uint_least64_t seed64(uint_least32_t *state)
+{
+	uint_least64_t x;
+
+	x = splitmix32(state);
+	return (x << 32) | splitmix32(state);
+}
 
+#if !TEST_RNG_NO_EXTERNAL_API
 struct test_rng *test_rng_alloc(const char *seed_str)
 {
-	unsigned long long seed;
+	test_uintmax seed_val;
 	struct test_rng *rng;
-	char *end;
+	uint_least32_t seed;
 
-	errno = 0;
-	seed = STRTOULL(seed_str, &end, 0);
-	if (*end != 0) {
-		fprintf(stderr, "%s: invalid seed\n", seed_str);
-		return NULL;
-	} else if (errno != 0) {
-		fprintf(stderr, "%s: invalid seed: %s\n",
-		                seed_str, strerror(errno));
+	if (!test_strtoumax(&seed_val, seed_str, 0xffffffff)) {
+		print_error("%s: invalid seed", seed_str);
 		return NULL;
 	}
+	seed = seed_val;
 
 	rng = malloc_nofail(sizeof *rng);
-	rng->state[0] = splitmix64(&seed);
-	rng->state[1] = splitmix64(&seed);
-	rng->state[2] = splitmix64(&seed);
-	rng->state[3] = splitmix64(&seed);
+	rng->state[0] = seed64(&seed);
+	rng->state[1] = seed64(&seed);
+	rng->state[2] = seed64(&seed);
+	rng->state[3] = seed64(&seed);
 
 	return rng;
 }
@@ -116,20 +116,6 @@ void test_rng_free(struct test_rng *rng)
 	free(rng);
 }
 
-#define BITS_PER_FP_DIGIT ( FLT_RADIX <  4 ? 1 \
-	                  : FLT_RADIX <  8 ? 2 \
-	                  : FLT_RADIX < 16 ? 3 \
-	                  : FLT_RADIX < 32 ? 4 \
-	                  : 5 )
-
-double test_rng_uniform(struct test_rng *rng)
-{
-	unsigned long long val = xoshiro256p(rng->state);
-	int prec = MIN(64, DBL_MANT_DIG*BITS_PER_FP_DIGIT);
-
-	return ldexp(val >> (64-prec), -prec);
-}
-
 /* Calculate the least power of two greater than val, minus 1. */
 static unsigned rng_mask(unsigned val)
 {
@@ -155,3 +141,4 @@ unsigned test_rng_uniform_int(struct test_rng *rng, unsigned max)
 
 	return val;
 }
+#endif