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/* $OpenBSD: s_casinl.c,v 1.5 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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/* casinl() |
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* |
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* Complex circular arc sine |
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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 casinl(); |
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* long double complex z, w; |
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* |
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* w = casinl( 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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* Inverse complex sine: |
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* |
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* 2 |
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* w = -i clog( iz + csqrt( 1 - z ) ). |
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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 10100 2.1e-15 3.4e-16 |
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* IEEE -10,+10 30000 2.2e-14 2.7e-15 |
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* Larger relative error can be observed for z near zero. |
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* Also tested by csin(casin(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 PIO2L = 1.570796326794896619231321691639751442098585L; |
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long double complex |
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casinl(long double complex z) |
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{ |
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long double complex w; |
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long double x, y, b; |
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static long double complex ca, ct, zz, z2; |
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x = creall(z); |
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y = cimagl(z); |
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#if 0 |
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if (y == 0.0L) { |
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if (fabsl(x) > 1.0L) { |
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w = PIO2L + 0.0L * I; |
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/*mtherr( "casinl", DOMAIN );*/ |
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} |
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else { |
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w = asinl(x) + 0.0L * I; |
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} |
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return (w); |
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} |
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#endif |
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/* Power series expansion */ |
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b = cabsl(z); |
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if (b < 0.125L) { |
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long double complex sum; |
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long double n, cn; |
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z2 = (x - y) * (x + y) + (2.0L * x * y) * I; |
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cn = 1.0L; |
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n = 1.0L; |
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ca = x + y * I; |
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sum = x + y * I; |
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do { |
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ct = z2 * ca; |
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ca = ct; |
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cn *= n; |
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n += 1.0L; |
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cn /= n; |
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n += 1.0L; |
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b = cn/n; |
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ct *= b; |
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sum += ct; |
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b = cabsl(ct); |
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} |
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while (b > MACHEPL); |
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w = sum; |
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return w; |
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} |
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ca = x + y * I; |
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ct = ca * I; /* iz */ |
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/* sqrt(1 - z*z) */ |
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/* cmul(&ca, &ca, &zz) */ |
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/* x * x - y * y */ |
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zz = (x - y) * (x + y) + (2.0L * x * y) * I; |
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zz = 1.0L - creall(zz) - cimagl(zz) * I; |
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z2 = csqrtl(zz); |
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zz = ct + z2; |
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zz = clogl(zz); |
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/* multiply by 1/i = -i */ |
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w = zz * (-1.0L * I); |
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return (w); |
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} |
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DEF_STD(casinl); |