pxfm/
asinpif.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;
30
31pub(crate) static ASINCOSF_PI_TABLE: [[u64; 8]; 16] = [
32    [
33        0x3fd45f306dc9c882,
34        0x3fab2995e7b7dc2f,
35        0x3f98723a1cf50c7e,
36        0x3f8d1a4591d16a29,
37        0x3f83ce3aa68ddaee,
38        0x3f7d3182ab0cc1bf,
39        0x3f762b379a8b88e3,
40        0x3f76811411fcfec2,
41    ],
42    [
43        0x3fdffffffffd3cda,
44        0xbfb17cc1b3355fdd,
45        0x3f9d067a1e8d5a99,
46        0xbf908e16fb09314a,
47        0x3f85eed43d42dcb2,
48        0xbf7f58baca7acc71,
49        0x3f75dab64e2dcf15,
50        0xbf659270e30797ac,
51    ],
52    [
53        0x3fdfffffff7c4617,
54        0xbfb17cc149ded3a2,
55        0x3f9d0654d4cb2c1a,
56        0xbf908c3ba713d33a,
57        0x3f85d2053481079c,
58        0xbf7e485ebc545e7e,
59        0x3f7303baca167ddd,
60        0xbf5dee8d16d06b38,
61    ],
62    [
63        0x3fdffffffa749848,
64        0xbfb17cbe71559350,
65        0x3f9d05a312269adf,
66        0xbf90862b3ee617d7,
67        0x3f85920708db2a73,
68        0xbf7cb0463b3862c3,
69        0x3f702b82478f95d7,
70        0xbf552a7b8579e729,
71    ],
72    [
73        0x3fdfffffe1f92bb5,
74        0xbfb17cb3e74c64e3,
75        0x3f9d03af67311cbf,
76        0xbf9079441cbfc7a0,
77        0x3f852b4287805a61,
78        0xbf7ac3286d604a98,
79        0x3f6b2f1210d9701b,
80        0xbf4e740ddc25afd6,
81    ],
82    [
83        0x3fdfffff92beb6e2,
84        0xbfb17c986fe9518b,
85        0x3f9cff98167c9a5e,
86        0xbf90638b591eae52,
87        0x3f84a0803828959e,
88        0xbf78adeca229f11d,
89        0x3f66b9a7ba05dfce,
90        0xbf4640521a43b2d0,
91    ],
92    [
93        0x3fdffffeccee5bfc,
94        0xbfb17c5f1753f5ea,
95        0x3f9cf874e4fe258f,
96        0xbf9043e6cf77b256,
97        0x3f83f7db42227d92,
98        0xbf7691a6fa2a2882,
99        0x3f62f6543162bc61,
100        0xbf407d5da05822b6,
101    ],
102    [
103        0x3fdffffd2f64431d,
104        0xbfb17bf8208c10c1,
105        0x3f9ced7487cdb124,
106        0xbf901a0d30932905,
107        0x3f83388f99b254da,
108        0xbf74844e245c65bd,
109        0x3f5fa777150197c6,
110        0xbf38c1ecf16a05c8,
111    ],
112    [
113        0x3fdffffa36d1712e,
114        0xbfb17b523971bd4e,
115        0x3f9cddee26de2dee,
116        0xbf8fccb00abaaabc,
117        0x3f8269afc3622342,
118        0xbf72933152686752,
119        0x3f5a76d4956cc9a3,
120        0xbf32ce7d6dc651ce,
121    ],
122    [
123        0x3fdffff5402ab3a1,
124        0xbfb17a5ba85da77a,
125        0x3f9cc96894e05c02,
126        0xbf8f532143cb832e,
127        0x3f819180b660ff09,
128        0xbf70c57417a78b3c,
129        0x3f562e26cbd7bb1e,
130        0xbf2ce28d33fe1df3,
131    ],
132    [
133        0x3fdfffed8d639751,
134        0xbfb1790349f3ae76,
135        0x3f9caf9a4fd1b398,
136        0xbf8ec986b111342e,
137        0x3f80b53c3ad4baa4,
138        0xbf6e3c2282eeace4,
139        0x3f52a55369f55bbe,
140        0xbf2667fe48c396e8,
141    ],
142    [
143        0x3fdfffe24b714161,
144        0xbfb177394fbcb719,
145        0x3f9c90652d920ebd,
146        0xbf8e3239197bddf1,
147        0x3f7fb2188525b025,
148        0xbf6b3aadd451afc7,
149        0x3f4f74020f31fdab,
150        0xbf218b0cb246768d,
151    ],
152    [
153        0x3fdfffd298bec9e2,
154        0xbfb174efbfd34648,
155        0x3f9c6bcfe48ea92b,
156        0xbf8d8f9f2a16157c,
157        0x3f7e0044f56c8864,
158        0xbf6883e2347fe76c,
159        0x3f4a9f0e3c1b7af5,
160        0xbf1bb5acc0e60825,
161    ],
162    [
163        0x3fdfffbd8b784c4d,
164        0xbfb1721abdd3722e,
165        0x3f9c41fee756d4b0,
166        0xbf8ce40bccf8065f,
167        0x3f7c59b684b70ef9,
168        0xbf66133d027996b3,
169        0x3f469cad01106397,
170        0xbf160f8e45494156,
171    ],
172    [
173        0x3fdfffa23749cf88,
174        0xbfb16eb0a8285c06,
175        0x3f9c132d762e1b0d,
176        0xbf8c31a959398f4e,
177        0x3f7ac1c5b46bc8a0,
178        0xbf63e34f1abe51dc,
179        0x3f4346738737c0b9,
180        0xbf11b227a3f5c750,
181    ],
182    [
183        0x3fdfff7fb25bb407,
184        0xbfb16aaa14d75640,
185        0x3f9bdfa75fca5ff2,
186        0xbf8b7a6e260d079c,
187        0x3f793ab06911033c,
188        0xbf61ee5560967fd5,
189        0x3f407d31060838bf,
190        0xbf0c96f33a283115,
191    ],
192];
193
194/// Computes asin(x)/PI
195///
196/// Max ULP 0.5
197#[inline]
198pub fn f_asinpif(x: f32) -> f32 {
199    let ax = x.abs();
200    let az = ax as f64;
201    let z = x as f64;
202    let t = x.to_bits();
203    let e: i32 = ((t >> 23) & 0xff) as i32;
204    if e >= 127 {
205        // |x| >= 1 or nan
206        if ax == 1.0 {
207            return f32::copysign(0.5, x);
208        } // |x| = 1
209        if e == 0xff && (t.wrapping_shl(9)) != 0 {
210            return x + x;
211        } // x = nan
212        return f32::NAN; // |x| > 1
213    }
214    let s: i32 = 146i32.wrapping_sub(e);
215    let mut i = 0i32;
216    // s<32 corresponds to |x| >= 2^-12
217    if s < 32 {
218        i = (((t & 0x007fffff) | 1 << 23) >> s) as i32;
219    }
220    let z2 = z * z;
221    let z4 = z2 * z2;
222    let c = ASINCOSF_PI_TABLE[i as usize & 15];
223    if i == 0 {
224        // |x| < 2^-4
225        let mut c0 = f_fmla(z2, f64::from_bits(c[1]), f64::from_bits(c[0]));
226        let c2 = f_fmla(z2, f64::from_bits(c[3]), f64::from_bits(c[2]));
227        let mut c4 = f_fmla(z2, f64::from_bits(c[5]), f64::from_bits(c[4]));
228        let c6 = f_fmla(z2, f64::from_bits(c[7]), f64::from_bits(c[6]));
229        c0 = f_fmla(c2, z4, c0);
230        c4 = f_fmla(c6, z4, c4);
231        c0 += c4 * (z4 * z4);
232        (z * c0) as f32
233    } else {
234        // |x| >= 2^-4
235        let f = (1. - az).sqrt();
236        let mut c0 = f_fmla(az, f64::from_bits(c[1]), f64::from_bits(c[0]));
237        let c2 = f_fmla(az, f64::from_bits(c[3]), f64::from_bits(c[2]));
238        let mut c4 = f_fmla(az, f64::from_bits(c[5]), f64::from_bits(c[4]));
239        let c6 = f_fmla(az, f64::from_bits(c[7]), f64::from_bits(c[6]));
240        c0 = f_fmla(c2, z2, c0);
241        c4 = f_fmla(c6, z2, c4);
242        c0 += c4 * z4;
243        let r = f_fmla(
244            -c0,
245            f64::copysign(f, x as f64),
246            f64::copysign(0.5, x as f64),
247        );
248        r as f32
249    }
250}
251
252#[cfg(test)]
253mod tests {
254    use super::*;
255
256    #[test]
257    fn test_asinpif() {
258        assert_eq!(f_asinpif(0.0), 0.);
259        assert_eq!(f_asinpif(0.5), 0.16666667);
260        assert!(f_asinpif(1.5).is_nan());
261    }
262}
pxfm/asinpif.rs

pxfm/
asinpif.rs
