diff options
Diffstat (limited to 'pl/math/log1pf_2u1.c')
| -rw-r--r-- | pl/math/log1pf_2u1.c | 15 |
1 files changed, 4 insertions, 11 deletions
diff --git a/pl/math/log1pf_2u1.c b/pl/math/log1pf_2u1.c index 5b0d542..9b7cb94 100644 --- a/pl/math/log1pf_2u1.c +++ b/pl/math/log1pf_2u1.c @@ -5,6 +5,7 @@ */ #include "math_config.h" +#include "hornerf.h" #define Ln2 (0x1.62e43p-1f) #define SignMask (0x80000000) @@ -21,8 +22,8 @@ eval_poly (float m, uint32_t e) { #ifdef LOG1PF_2U5 - /* 2.5 ulp variant. Approximate log(1+m) on [-0.25, 0.5] using Estrin - scheme. */ + /* 2.5 ulp variant. Approximate log(1+m) on [-0.25, 0.5] using + slightly modified Estrin scheme (no x^0 term, and x term is just x). */ float p_12 = fmaf (m, C (1), C (0)); float p_34 = fmaf (m, C (3), C (2)); float p_56 = fmaf (m, C (5), C (4)); @@ -49,15 +50,7 @@ eval_poly (float m, uint32_t e) x + C1 * x^2 + C2 * x^3 + C3 * x^4 + ... Hence approximation has the form m + m^2 * P(m) where P(x) = C1 + C2 * x + C3 * x^2 + ... . */ - float p = fmaf (C (8), m, C (7)); - p = fmaf (p, m, C (6)); - p = fmaf (p, m, C (5)); - p = fmaf (p, m, C (4)); - p = fmaf (p, m, C (3)); - p = fmaf (p, m, C (2)); - p = fmaf (p, m, C (1)); - p = fmaf (p, m, C (0)); - return fmaf (m, m * p, m); + return fmaf (m, m * HORNER_8 (m, C), m); #else #error No log1pf approximation exists with the requested precision. Options are 13 or 25. |