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;
69 /* Handle special cases. */
71 return (CMPLXL(0, b));
73 return (CMPLXL(INFINITY, b));
75 t = (b - b) / (b - b); /* raise invalid if b is not a NaN */
76 return (CMPLXL(a, t)); /* return NaN + NaN i */
80 * csqrt(inf + NaN i) = inf + NaN i
81 * csqrt(inf + y i) = inf + 0 i
82 * csqrt(-inf + NaN i) = NaN +- inf i
83 * csqrt(-inf + y i) = 0 + inf i
86 return (CMPLXL(fabsl(b - b), copysignl(a, b)));
88 return (CMPLXL(a, copysignl(b - b, b)));
91 * The remaining special case (b is NaN) is handled just fine by
92 * the normal code path below.
95 /* Scale to avoid overflow. */
96 if (fabsl(a) >= THRESH || fabsl(b) >= THRESH) {
104 /* Algorithm 312, CACM vol 10, Oct 1967. */
106 t = sqrtl((a + hypotl(a, b)) * 0.5);
107 result = CMPLXL(t, b / (2 * t));
109 t = sqrtl((-a + hypotl(a, b)) * 0.5);
110 result = CMPLXL(fabsl(b) / (2 * t), copysignl(t, b));