1 /* $NetBSD: csqrtf.c,v 1.1 2007/08/20 16:01:37 drochner Exp $ */
2
3 /*-
4 * Copyright (c) 2007 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software written by Stephen L. Moshier.
8 * It is redistributed by the NetBSD Foundation by permission of the author.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 *
31 * imported and modified include for newlib 2010/10/03
32 * Marco Atzeri <marco_atzeri@yahoo.it>
33 */
34
35 #include <complex.h>
36 #include <math.h>
37
38 float complex
csqrtf(float complex z)39 csqrtf(float complex z)
40 {
41 float complex w;
42 float x, y, r, t, scale;
43
44 x = crealf (z);
45 y = cimagf (z);
46
47 if (y == 0.0f) {
48 if (x < 0.0f) {
49 w = 0.0f + sqrtf(-x) * I;
50 return w;
51 } else if (x == 0.0f) {
52 return (0.0f + y * I);
53 } else {
54 w = sqrtf(x) + y * I;
55 return w;
56 }
57 }
58
59 if (x == 0.0f) {
60 r = fabsf(y);
61 r = sqrtf(0.5f * r);
62 if (y > 0)
63 w = r + r * I;
64 else
65 w = r - r * I;
66 return w;
67 }
68
69 /* Rescale to avoid internal overflow or underflow. */
70 if ((fabsf(x) > 4.0f) || (fabsf(y) > 4.0f)) {
71 x *= 0.25f;
72 y *= 0.25f;
73 scale = 2.0f;
74 } else {
75 #if 1
76 x *= 6.7108864e7f; /* 2^26 */
77 y *= 6.7108864e7f;
78 scale = 1.220703125e-4f; /* 2^-13 */
79 #else
80 x *= 4.0f;
81 y *= 4.0f;
82 scale = 0.5f;
83 #endif
84 }
85 w = x + y * I;
86 r = cabsf(w);
87 if( x > 0 ) {
88 t = sqrtf(0.5f * r + 0.5f * x);
89 r = scale * fabsf((0.5f * y) / t);
90 t *= scale;
91 } else {
92 r = sqrtf(0.5f * r - 0.5f * x);
93 t = scale * fabsf((0.5f * y) / r);
94 r *= scale;
95 }
96
97 if (y < 0)
98 w = t - r * I;
99 else
100 w = t + r * I;
101 return w;
102 }
103
