pxfm/hyperbolic/
coshf.rs

1/*
2 * // Copyright (c) Radzivon Bartoshyk 6/2025. All rights reserved.
3 * //
4 * // Redistribution and use in source and binary forms, with or without modification,
5 * // are permitted provided that the following conditions are met:
6 * //
7 * // 1.  Redistributions of source code must retain the above copyright notice, this
8 * // list of conditions and the following disclaimer.
9 * //
10 * // 2.  Redistributions in binary form must reproduce the above copyright notice,
11 * // this list of conditions and the following disclaimer in the documentation
12 * // and/or other materials provided with the distribution.
13 * //
14 * // 3.  Neither the name of the copyright holder nor the names of its
15 * // contributors may be used to endorse or promote products derived from
16 * // this software without specific prior written permission.
17 * //
18 * // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
19 * // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
20 * // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
22 * // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
23 * // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
24 * // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
25 * // CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
26 * // OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
27 * // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29use crate::common::{f_fmla, f_fmlaf};
30use crate::round_ties_even::RoundTiesEven;
31use std::hint::black_box;
32
33static TB: [u64; 32] = [
34    0x3fe0000000000000,
35    0x3fe059b0d3158574,
36    0x3fe0b5586cf9890f,
37    0x3fe11301d0125b51,
38    0x3fe172b83c7d517b,
39    0x3fe1d4873168b9aa,
40    0x3fe2387a6e756238,
41    0x3fe29e9df51fdee1,
42    0x3fe306fe0a31b715,
43    0x3fe371a7373aa9cb,
44    0x3fe3dea64c123422,
45    0x3fe44e086061892d,
46    0x3fe4bfdad5362a27,
47    0x3fe5342b569d4f82,
48    0x3fe5ab07dd485429,
49    0x3fe6247eb03a5585,
50    0x3fe6a09e667f3bcd,
51    0x3fe71f75e8ec5f74,
52    0x3fe7a11473eb0187,
53    0x3fe82589994cce13,
54    0x3fe8ace5422aa0db,
55    0x3fe93737b0cdc5e5,
56    0x3fe9c49182a3f090,
57    0x3fea5503b23e255d,
58    0x3feae89f995ad3ad,
59    0x3feb7f76f2fb5e47,
60    0x3fec199bdd85529c,
61    0x3fecb720dcef9069,
62    0x3fed5818dcfba487,
63    0x3fedfc97337b9b5f,
64    0x3feea4afa2a490da,
65    0x3fef50765b6e4540,
66];
67
68#[cold]
69fn coshf_accurate(z: f64, ia: f64, sp: u64, sm: u64) -> f32 {
70    const CH: [u64; 7] = [
71        0x3ff0000000000000,
72        0x3f962e42fefa39ef,
73        0x3f2ebfbdff82c58f,
74        0x3ebc6b08d702e0ed,
75        0x3e43b2ab6fb92e5e,
76        0x3dc5d886e6d54203,
77        0x3d4430976b8ce6ef,
78    ];
79
80    const ILN2H: f64 = f64::from_bits(0x4047154765000000);
81    const ILN2L: f64 = f64::from_bits(0x3e55c17f0bbbe880);
82    let h = f_fmla(ILN2L, z, f_fmla(ILN2H, z, -ia));
83    let h2 = h * h;
84
85    let q0 = f_fmla(h2, f64::from_bits(CH[6]), f64::from_bits(CH[4]));
86    let q1 = f_fmla(h2, f64::from_bits(CH[2]), f64::from_bits(CH[0]));
87
88    let te = f_fmla(h2 * h2, q0, q1);
89
90    let j0 = f_fmla(h2, f64::from_bits(CH[5]), f64::from_bits(CH[3]));
91
92    let to = f_fmla(h2, j0, f64::from_bits(CH[1]));
93
94    let z0 = f_fmla(h, to, te);
95    let z1 = f_fmla(-h, to, te);
96    f_fmla(f64::from_bits(sp), z0, f64::from_bits(sm) * z1) as f32
97}
98
99/// Hyperbolic cos
100///
101/// Max found ULP 0.4999996
102#[inline]
103pub fn f_coshf(x: f32) -> f32 {
104    const C: [u64; 4] = [
105        0x3ff0000000000000,
106        0x3f962e42fef4c4e7,
107        0x3f2ebfd1b232f475,
108        0x3ebc6b19384ecd93,
109    ];
110
111    const I_LN2: f64 = f64::from_bits(0x40471547652b82fe);
112    let t = x.to_bits();
113    let z = x as f64;
114    let ax = t.wrapping_shl(1);
115    if ax > 0x8565a9f8u32 {
116        // |x| >~ 89.4
117        if ax >= 0xff000000u32 {
118            if ax.wrapping_shl(8) != 0 {
119                return x + x;
120            } // nan
121            return f32::INFINITY; // +-inf
122        }
123        let r = black_box(2.0) * black_box(f64::from_bits(0x47efffffe0000000) as f32);
124        return r;
125    }
126    if ax < 0x7c000000u32 {
127        // |x| < 0.125
128        if ax < 0x74000000u32 {
129            // |x| < 0.000488281
130            if ax < 0x66000000u32 {
131                // |x| < 5.96046e-08
132                return f_fmlaf(x.abs(), f64::from_bits(0x3e60000000000000) as f32, 1.0);
133            }
134            return f_fmlaf(0.5 * x, x, 1.0);
135        }
136        const CP: [u64; 4] = [
137            0x3fdfffffffffffe3,
138            0x3fa55555555723cf,
139            0x3f56c16bee4a5986,
140            0x3efa0483fc0328f7,
141        ];
142        let z2 = z * z;
143        let z4 = z2 * z2;
144        let w0 = f_fmla(z2, f64::from_bits(CP[1]), f64::from_bits(CP[0]));
145        let w1 = f_fmla(z2, f64::from_bits(CP[3]), f64::from_bits(CP[2]));
146        return f_fmla(z2, f_fmla(z4, w1, w0), 1.0) as f32;
147    }
148    let a = I_LN2 * z;
149    let ia = a.round_ties_even_finite();
150    let h = a - ia;
151    let h2 = h * h;
152    let ja = (ia + f64::from_bits(0x4338000000000000)).to_bits();
153    let jp: i64 = ja as i64;
154    let jm = -jp;
155    let sp = TB[(jp & 31) as usize].wrapping_add(jp.wrapping_shr(5).wrapping_shl(52) as u64);
156    let sm = TB[(jm & 31) as usize].wrapping_add(jm.wrapping_shr(5).wrapping_shl(52) as u64);
157    let te = f_fmla(h2, f64::from_bits(C[2]), f64::from_bits(C[0]));
158    let to = f_fmla(h2, f64::from_bits(C[3]), f64::from_bits(C[1]));
159    let rp = f64::from_bits(sp) * f_fmla(h, to, te);
160    let rm = f64::from_bits(sm) * f_fmla(-h, to, te);
161    let r = rp + rm;
162    let ub = r;
163    let lb = r - f64::from_bits(0x3de3edbbe4560327) * r;
164    // Ziv's accuracy test
165    if ub != lb {
166        return coshf_accurate(z, ia, sp, sm);
167    }
168    ub as f32
169}
170
171#[cfg(test)]
172mod tests {
173    use super::*;
174
175    #[test]
176    fn test_coshf() {
177        assert_eq!(f_coshf(-0.5), 1.127626);
178        assert_eq!(f_coshf(0.5), 1.127626);
179        assert_eq!(f_coshf(7.), 548.317);
180    }
181}
pxfm/hyperbolic/coshf.rs

pxfm/hyperbolic/
coshf.rs
