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