2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2007-2008 David Schultz <das@FreeBSD.ORG>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29 #include <sys/cdefs.h>
30 __FBSDID("$FreeBSD$");
36 #include "math_private.h"
39 * gcc doesn't implement complex multiplication or division correctly,
40 * so we need to handle infinities specially. We turn on this pragma to
41 * notify conforming c99 compilers that the fast-but-incorrect code that
42 * gcc generates is acceptable, since the special cases have already been
45 #pragma STDC CX_LIMITED_RANGE ON
48 * We risk spurious overflow for components >= LDBL_MAX / (1 + sqrt(2)).
49 * Rather than determining the fully precise value at which we might
50 * overflow, just use a threshold of approximately LDBL_MAX / 4.
52 #if LDBL_MAX_EXP != 0x4000
53 #error "Unsupported long double format"
55 #define THRESH 0x1p16382L
59 csqrtl(long double complex z)
61 long double complex result;
62 long double a, b, rx, ry, scale, t;
67 /* Handle special cases. */
69 return (CMPLXL(0, b));
71 return (CMPLXL(INFINITY, b));
73 t = (b - b) / (b - b); /* raise invalid if b is not a NaN */
74 return (CMPLXL(a + 0.0L + t, a + 0.0L + t)); /* NaN + NaN i */
78 * csqrt(inf + NaN i) = inf + NaN i
79 * csqrt(inf + y i) = inf + 0 i
80 * csqrt(-inf + NaN i) = NaN +- inf i
81 * csqrt(-inf + y i) = 0 + inf i
84 return (CMPLXL(fabsl(b - b), copysignl(a, b)));
86 return (CMPLXL(a, copysignl(b - b, b)));
89 t = (a - a) / (a - a); /* raise invalid */
90 return (CMPLXL(b + 0.0L + t, b + 0.0L + t)); /* NaN + NaN i */
93 /* Scale to avoid overflow. */
94 if (fabsl(a) >= THRESH || fabsl(b) >= THRESH) {
96 * Don't scale a or b if this might give (spurious)
97 * underflow. Then the unscaled value is an equivalent
98 * infinitesmal (or 0).
100 if (fabsl(a) >= 0x1p-16380L)
102 if (fabsl(b) >= 0x1p-16380L)
109 /* Scale to reduce inaccuracies when both components are denormal. */
110 if (fabsl(a) < 0x1p-16382L && fabsl(b) < 0x1p-16382L) {
116 /* Algorithm 312, CACM vol 10, Oct 1967. */
118 t = sqrtl((a + hypotl(a, b)) * 0.5);
122 t = sqrtl((-a + hypotl(a, b)) * 0.5);
123 rx = fabsl(b) / (2 * t);
124 ry = copysignl(t, b);
127 return (CMPLXL(rx * scale, ry * scale));