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Last active October 17, 2023 11:46
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/* See: https://mumble.net/~campbell/2014/04/28/uniform-random-float */
/* See: https://allendowney.com/research/rand/downey07randfloat.pdf */
double randf_3a() {
double d;
uint64_t u = rand_next();
uint64_t exp = __builtin_ctzll(u | (1 << 12)) - 1022ull;
u = (((u >> 11) + 1) >> 1) - (exp << 52);
memcpy(&d, &u, sizeof(d));
return d;
}
double randf_3b() {
double d;
uint64_t u = rand_next();
uint64_t exp = __builtin_ctzll(u) - 11ull;
if ((int64_t)exp >= 0) exp = __builtin_ctzll(rand_next());
u = (((u >> 11) + 1) >> 1) - ((exp - 1011ull) << 52);
memcpy(&d, &u, sizeof(d));
return d;
}
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