diff options
Diffstat (limited to 'vendor/libm-0.1.4/src/math/k_tanf.rs')
-rw-r--r-- | vendor/libm-0.1.4/src/math/k_tanf.rs | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/vendor/libm-0.1.4/src/math/k_tanf.rs b/vendor/libm-0.1.4/src/math/k_tanf.rs new file mode 100644 index 000000000..52651378d --- /dev/null +++ b/vendor/libm-0.1.4/src/math/k_tanf.rs @@ -0,0 +1,47 @@ +/* origin: FreeBSD /usr/src/lib/msun/src/k_tan.c */ +/* + * ==================================================== + * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved. + * + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* |tan(x)/x - t(x)| < 2**-25.5 (~[-2e-08, 2e-08]). */ +const T: [f64; 6] = [ + 0.333331395030791399758, /* 0x15554d3418c99f.0p-54 */ + 0.133392002712976742718, /* 0x1112fd38999f72.0p-55 */ + 0.0533812378445670393523, /* 0x1b54c91d865afe.0p-57 */ + 0.0245283181166547278873, /* 0x191df3908c33ce.0p-58 */ + 0.00297435743359967304927, /* 0x185dadfcecf44e.0p-61 */ + 0.00946564784943673166728, /* 0x1362b9bf971bcd.0p-59 */ +]; + +#[inline] +#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)] +pub(crate) fn k_tanf(x: f64, odd: bool) -> f32 { + let z = x * x; + /* + * Split up the polynomial into small independent terms to give + * opportunities for parallel evaluation. The chosen splitting is + * micro-optimized for Athlons (XP, X64). It costs 2 multiplications + * relative to Horner's method on sequential machines. + * + * We add the small terms from lowest degree up for efficiency on + * non-sequential machines (the lowest degree terms tend to be ready + * earlier). Apart from this, we don't care about order of + * operations, and don't need to to care since we have precision to + * spare. However, the chosen splitting is good for accuracy too, + * and would give results as accurate as Horner's method if the + * small terms were added from highest degree down. + */ + let mut r = T[4] + z * T[5]; + let t = T[2] + z * T[3]; + let w = z * z; + let s = z * x; + let u = T[0] + z * T[1]; + r = (x + s * u) + (s * w) * (t + w * r); + (if odd { -1. / r } else { r }) as f32 +} |