pxfm/
round_ties_even.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 */
29
30pub const fn roundf_ties_even(x: f32) -> f32 {
31    const BIAS: i32 = 0x7f;
32    const MANT_DIG: i32 = 24;
33    const MAX_EXP: i32 = 2 * BIAS + 1;
34    let mut ix: u32 = x.to_bits();
35    let ux: u32 = ix & 0x7fffffff;
36    let exponent: i32 = (ux >> (MANT_DIG - 1)) as i32;
37    if exponent >= BIAS + MANT_DIG - 1 {
38        /* Integer, infinity or NaN.  */
39        if exponent == MAX_EXP {
40            /* Infinity or NaN; quiet signaling NaNs.  */
41            return x + x;
42        } else {
43            return x;
44        }
45    } else if exponent >= BIAS {
46        /* At least 1; not necessarily an integer.  Locate the bits with
47        exponents 0 and -1 (when the unbiased exponent is 0, the bit
48        with exponent 0 is implicit, but as the bias is odd it is OK
49        to take it from the low bit of the exponent).  */
50        let int_pos: i32 = (BIAS + MANT_DIG - 1) - exponent;
51        let half_pos: i32 = int_pos - 1;
52        let half_bit: u32 = 1u32 << half_pos;
53        let int_bit: u32 = 1u32 << int_pos;
54        if (ix & (int_bit | (half_bit - 1))) != 0 {
55            /* Carry into the exponent works correctly.  No need to test
56            whether HALF_BIT is set.  */
57            ix = ix.wrapping_add(half_bit);
58        }
59        ix &= !(int_bit - 1);
60    } else if exponent == BIAS - 1 && ux > 0x3f000000 {
61        /* Interval (0.5, 1).  */
62        ix = (ix & 0x80000000) | 0x3f800000;
63    } else {
64        /* Rounds to 0.  */
65        ix &= 0x80000000;
66    }
67    f32::from_bits(ix)
68}
69
70pub const fn round_ties_even(x: f64) -> f64 {
71    let mut ix: u64 = x.to_bits();
72    let ux = ix & 0x7fffffffffffffffu64;
73    const BIAS: i32 = 0x3ff;
74    const MANT_DIG: i32 = 53;
75    const MAX_EXP: i32 = 2 * BIAS + 1;
76    let exponent: i32 = (ux >> (MANT_DIG - 1)) as i32;
77    if exponent >= BIAS + MANT_DIG - 1 {
78        /* Integer, infinity or NaN.  */
79        return if exponent == MAX_EXP {
80            /* Infinity or NaN; quiet signaling NaNs.  */
81            x + x
82        } else {
83            x
84        };
85    } else if exponent >= BIAS {
86        /* At least 1; not necessarily an integer.  Locate the bits with
87        exponents 0 and -1 (when the unbiased exponent is 0, the bit
88        with exponent 0 is implicit, but as the bias is odd it is OK
89        to take it from the low bit of the exponent).  */
90        let int_pos: i32 = (BIAS + MANT_DIG - 1) - exponent;
91        let half_pos: i32 = int_pos - 1;
92        let half_bit: u64 = 1u64 << half_pos;
93        let int_bit: u64 = 1u64 << int_pos;
94        if (ix & (int_bit | (half_bit - 1))) != 0 {
95            /* Carry into the exponent works correctly.  No need to test
96            whether HALF_BIT is set.  */
97            ix = ix.wrapping_add(half_bit);
98        }
99        ix &= !(int_bit - 1);
100    } else if exponent == BIAS - 1 && ux > 0x3fe0000000000000u64 {
101        /* Interval (0.5, 1).  */
102        ix = (ix & 0x8000000000000000u64) | 0x3ff0000000000000u64;
103    } else {
104        /* Rounds to 0.  */
105        ix &= 0x8000000000000000u64;
106    }
107    f64::from_bits(ix)
108}
109
110pub(crate) trait RoundTiesEven {
111    fn round_ties_even_finite(self) -> Self;
112}
113
114impl RoundTiesEven for f32 {
115    #[inline]
116    fn round_ties_even_finite(self) -> Self {
117        #[cfg(any(
118            all(
119                any(target_arch = "x86", target_arch = "x86_64"),
120                target_feature = "sse4.1"
121            ),
122            target_arch = "aarch64"
123        ))]
124        {
125            self.round_ties_even()
126        }
127        #[cfg(not(any(
128            all(
129                any(target_arch = "x86", target_arch = "x86_64"),
130                target_feature = "sse4.1"
131            ),
132            target_arch = "aarch64"
133        )))]
134        {
135            roundf_ties_even(self)
136        }
137    }
138}
139
140impl RoundTiesEven for f64 {
141    #[inline]
142    fn round_ties_even_finite(self) -> Self {
143        #[cfg(any(
144            all(
145                any(target_arch = "x86", target_arch = "x86_64"),
146                target_feature = "sse4.1"
147            ),
148            target_arch = "aarch64"
149        ))]
150        {
151            self.round_ties_even()
152        }
153        #[cfg(not(any(
154            all(
155                any(target_arch = "x86", target_arch = "x86_64"),
156                target_feature = "sse4.1"
157            ),
158            target_arch = "aarch64"
159        )))]
160        {
161            round_ties_even(self)
162        }
163    }
164}
165
166#[cfg(test)]
167mod tests {
168    use super::*;
169
170    #[test]
171    fn test_roundf_ties_even() {
172        assert_eq!(roundf_ties_even(0f32), 0.0f32.round_ties_even());
173        assert_eq!(roundf_ties_even(0.5f32), 0.5f32.round_ties_even());
174        assert_eq!(roundf_ties_even(-0.5), (-0.5f32).round_ties_even());
175        assert_eq!(roundf_ties_even(1f32), 1.0f32.round_ties_even());
176        assert_eq!(roundf_ties_even(1.2f32), 1.2f32.round_ties_even());
177        assert_eq!(roundf_ties_even(-1.2f32), (-1.2f32).round_ties_even());
178        assert_eq!(roundf_ties_even(-1.6f32), (-1.6f32).round_ties_even());
179        assert_eq!(roundf_ties_even(-1.5f32), (-1.5f32).round_ties_even());
180        assert_eq!(roundf_ties_even(1.6f32), 1.6f32.round_ties_even());
181        assert_eq!(roundf_ties_even(1.5f32), 1.5f32.round_ties_even());
182        assert_eq!(roundf_ties_even(2.5f32), 2.5f32.round_ties_even());
183        assert_eq!(
184            roundf_ties_even(f32::INFINITY),
185            f32::INFINITY.round_ties_even()
186        );
187        assert_eq!(
188            roundf_ties_even(f32::NEG_INFINITY),
189            f32::NEG_INFINITY.round_ties_even()
190        );
191        assert!(roundf_ties_even(f32::NAN).is_nan());
192    }
193
194    #[test]
195    fn test_round_ties_even() {
196        assert_eq!(
197            round_ties_even(5.6916e-320),
198            (5.6916e-320f64).round_ties_even()
199        );
200        assert_eq!(round_ties_even(3f64), 3f64.round_ties_even());
201        assert_eq!(round_ties_even(2f64), 2f64.round_ties_even());
202        assert_eq!(round_ties_even(0.), 0.0f64.round_ties_even());
203        assert_eq!(round_ties_even(0.5), 0.5f64.round_ties_even());
204        assert_eq!(round_ties_even(-0.5), (-0.5f64).round_ties_even());
205        assert_eq!(round_ties_even(1.), 1.0f64.round_ties_even());
206        assert_eq!(round_ties_even(1.2), 1.2f64.round_ties_even());
207        assert_eq!(round_ties_even(-1.2), (-1.2f64).round_ties_even());
208        assert_eq!(round_ties_even(-1.6), (-1.6f64).round_ties_even());
209        assert_eq!(round_ties_even(-1.5), (-1.5f64).round_ties_even());
210        assert_eq!(round_ties_even(1.6), 1.6f64.round_ties_even());
211        assert_eq!(round_ties_even(1.5), 1.5f64.round_ties_even());
212        assert_eq!(round_ties_even(2.5), 2.5f64.round_ties_even());
213        assert_eq!(round_ties_even(-2.5), (-2.5f64).round_ties_even());
214        assert_eq!(
215            round_ties_even(f64::INFINITY),
216            f64::INFINITY.round_ties_even()
217        );
218        assert_eq!(
219            round_ties_even(f64::NEG_INFINITY),
220            f64::NEG_INFINITY.round_ties_even()
221        );
222        assert!(round_ties_even(f64::NAN).is_nan());
223    }
224}
pxfm/round_ties_even.rs

pxfm/
round_ties_even.rs
