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/* $OpenBSD: s_ctanl.c,v 1.3 2011/07/20 21:02:51 martynas 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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/* ctanl() |
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* |
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* Complex circular 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 ctanl(); |
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* long double complex z, w; |
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* |
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* w = ctanl( 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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* |
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* sin 2x + i sinh 2y |
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* w = --------------------. |
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* cos 2x + cosh 2y |
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* |
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* On the real axis the denominator is zero at odd multiples |
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* of PI/2. The denominator is evaluated by its Taylor |
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* series near these points. |
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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 5200 7.1e-17 1.6e-17 |
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* IEEE -10,+10 30000 7.2e-16 1.2e-16 |
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* Also tested by ctan * ccot = 1 and catan(ctan(z)) = z. |
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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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#if LDBL_MANT_DIG == 64 |
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static const long double MACHEPL= 5.42101086242752217003726400434970855712890625E-20L; |
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#elif LDBL_MANT_DIG == 113 |
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static const long double MACHEPL = 9.629649721936179265279889712924636592690508e-35L; |
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#endif |
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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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static long double |
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ctansl(long double complex z) |
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{ |
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long double f, x, x2, y, y2, rn, t; |
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long double d; |
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x = fabsl(2.0L * creall(z)); |
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y = fabsl(2.0L * cimagl(z)); |
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x = redupil(x); |
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x = x * x; |
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y = y * y; |
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x2 = 1.0L; |
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y2 = 1.0L; |
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f = 1.0L; |
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rn = 0.0L; |
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d = 0.0L; |
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do { |
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rn += 1.0L; |
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f *= rn; |
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rn += 1.0L; |
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f *= rn; |
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x2 *= x; |
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y2 *= y; |
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t = y2 + x2; |
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t /= f; |
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d += t; |
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rn += 1.0L; |
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f *= rn; |
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rn += 1.0L; |
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f *= rn; |
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x2 *= x; |
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y2 *= y; |
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t = y2 - x2; |
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t /= f; |
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d += t; |
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} |
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while (fabsl(t/d) > MACHEPL); |
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return(d); |
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} |
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long double complex |
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ctanl(long double complex z) |
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{ |
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long double complex w; |
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long double d, x, y; |
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x = creall(z); |
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y = cimagl(z); |
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d = cosl(2.0L * x) + coshl(2.0L * y); |
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if (fabsl(d) < 0.25L) { |
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d = fabsl(d); |
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d = ctansl(z); |
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} |
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if (d == 0.0L) { |
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/*mtherr( "ctan", 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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w = sinl(2.0L * x) / d + (sinhl(2.0L * y) / d) * I; |
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return (w); |
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} |