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/* $OpenBSD: s_catanl.c,v 1.4 2016/09/12 19:47:02 guenther Exp $ */ |
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/* |
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* Copyright (c) 2008 Stephen L. Moshier <steve@moshier.net> |
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* |
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* Permission to use, copy, modify, and distribute this software for any |
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* purpose with or without fee is hereby granted, provided that the above |
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* copyright notice and this permission notice appear in all copies. |
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* |
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR |
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN |
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF |
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. |
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*/ |
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/* catanl() |
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* |
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* Complex circular arc tangent |
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* |
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* |
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* |
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* SYNOPSIS: |
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* |
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* long double complex catanl(); |
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* long double complex z, w; |
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* |
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* w = catanl( z ); |
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* |
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* |
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* |
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* DESCRIPTION: |
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* |
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* If |
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* z = x + iy, |
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* |
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* then |
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* 1 ( 2x ) |
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* Re w = - arctan(-----------) + k PI |
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* 2 ( 2 2) |
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* (1 - x - y ) |
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* |
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* ( 2 2) |
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* 1 (x + (y+1) ) |
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* Im w = - log(------------) |
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* 4 ( 2 2) |
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* (x + (y-1) ) |
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* |
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* Where k is an arbitrary integer. |
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* |
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* |
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* |
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* ACCURACY: |
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* |
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* Relative error: |
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* arithmetic domain # trials peak rms |
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* DEC -10,+10 5900 1.3e-16 7.8e-18 |
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* IEEE -10,+10 30000 2.3e-15 8.5e-17 |
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* The check catan( ctan(z) ) = z, with |x| and |y| < PI/2, |
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* had peak relative error 1.5e-16, rms relative error |
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* 2.9e-17. See also clog(). |
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*/ |
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#include <complex.h> |
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#include <float.h> |
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#include <math.h> |
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static const long double PIL = 3.141592653589793238462643383279502884197169L; |
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static const long double DP1 = 3.14159265358979323829596852490908531763125L; |
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static const long double DP2 = 1.6667485837041756656403424829301998703007e-19L; |
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static const long double DP3 = 1.8830410776607851167459095484560349402753e-39L; |
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static long double |
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redupil(long double x) |
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{ |
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long double t; |
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long i; |
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t = x / PIL; |
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if (t >= 0.0L) |
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t += 0.5L; |
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else |
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t -= 0.5L; |
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i = t; /* the multiple */ |
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t = i; |
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t = ((x - t * DP1) - t * DP2) - t * DP3; |
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return (t); |
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} |
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long double complex |
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catanl(long double complex z) |
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{ |
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long double complex w; |
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long double a, t, x, x2, y; |
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x = creall(z); |
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y = cimagl(z); |
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if ((x == 0.0L) && (y > 1.0L)) |
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goto ovrf; |
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x2 = x * x; |
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a = 1.0L - x2 - (y * y); |
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if (a == 0.0L) |
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goto ovrf; |
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t = atan2l(2.0L * x, a) * 0.5L; |
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w = redupil(t); |
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t = y - 1.0L; |
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a = x2 + (t * t); |
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if (a == 0.0L) |
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goto ovrf; |
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t = y + 1.0L; |
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a = (x2 + (t * t)) / a; |
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w = w + (0.25L * logl(a)) * I; |
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return (w); |
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ovrf: |
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/*mtherr( "catanl", OVERFLOW );*/ |
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w = LDBL_MAX + LDBL_MAX * I; |
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return (w); |
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} |
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DEF_STD(catanl); |