ref: 0113cd12d5ce3faae500772c76018f0ad4dd776a
dir: /lib/math/ancillary/log-overkill-tests.c/
/* cc -o log-overkill-tests log-overkill-tests.c -lmpfr */ #include <stdint.h> #include <stdio.h> #include <time.h> #include <mpfr.h> #define FLT64_TO_UINT64(f) (*((uint64_t *) ((char *) &f))) #define UINT64_TO_FLT64(u) (*((double *) ((char *) &u))) #define FLT32_TO_UINT32(f) (*((uint32_t *) ((char *) &f))) #define UINT32_TO_FLT32(u) (*((float *) ((char *) &u))) /* xoroshiro64**, from http://xoshiro.di.unimi.it/xoroshiro64starstar.c and in public domain. */ static inline uint32_t rotl(const uint32_t x, int k) { return (x << k) | (x >> (32 - k)); } static uint32_t s[2]; uint32_t next(void) { const uint32_t s0 = s[0]; uint32_t s1 = s[1]; const uint32_t result_starstar = rotl(s0 * 0x9E3779BB, 5) * 5; s1 ^= s0; s[0] = rotl(s0, 26) ^ s1 ^ (s1 << 9); s[1] = rotl(s1, 13); return result_starstar; } int main(void) { mpfr_t x; mpfr_t lnx; mpfr_t t; double d = 0; float f = 0; double t1 = 0; double t2 = 0; float t3 = 0; float t4 = 0; uint64_t u = 0; uint32_t v = 0; /* Seed xoroshiro64** */ s[1] = 1234; s[2] = 1234; mpfr_init2(x, 10000); mpfr_init2(t, 10000); mpfr_init2(lnx, 10000); size_t n = 0; while (n < 100) { u = (((uint64_t)next()) << 32) | ((uint64_t)next()); d = UINT64_TO_FLT64(u); if (d < 0.001 || d > 100) { continue; } printf("(%#018lx, ", u); mpfr_set_d(x, d, MPFR_RNDN); mpfr_log(lnx, x, MPFR_RNDN); t1 = mpfr_get_d(lnx, MPFR_RNDN); mpfr_set_d(t, t1, MPFR_RNDN); mpfr_sub(lnx, lnx, t, MPFR_RNDN); t2 = mpfr_get_d(lnx, MPFR_RNDN); printf("%#018lx, %#018lx),\n", FLT64_TO_UINT64(t1), FLT64_TO_UINT64(t2)); n++; } n = 0; while (n < 100) { v = next(); f = UINT32_TO_FLT32(v); if (f < 0.001 || f > 100) { continue; } printf("(%#010x, ", v); mpfr_set_d(x, (double) f, MPFR_RNDN); mpfr_log(lnx, x, MPFR_RNDN); t3 = (float)mpfr_get_d(lnx, MPFR_RNDN); mpfr_set_d(t, (double) t3, MPFR_RNDN); mpfr_sub(lnx, lnx, t, MPFR_RNDN); t4 = (float)mpfr_get_d(lnx, MPFR_RNDN); printf("%#010x, %#010x),\n", FLT32_TO_UINT32(t3), FLT32_TO_UINT32(t4)); n++; } return 0; }