/* $NetBSD: n_j0.c,v 1.1 1995/10/10 23:36:52 ragge Exp $ */ /*- * Copyright (c) 1992, 1993 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #ifndef lint static char sccsid[] = "@(#)j0.c 8.2 (Berkeley) 11/30/93"; #endif /* not lint */ /* * 16 December 1992 * Minor modifications by Peter McIlroy to adapt non-IEEE architecture. */ /* * ==================================================== * Copyright (C) 1992 by Sun Microsystems, Inc. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== * * ******************* WARNING ******************** * This is an alpha version of SunPro's FDLIBM (Freely * Distributable Math Library) for IEEE double precision * arithmetic. FDLIBM is a basic math library written * in C that runs on machines that conform to IEEE * Standard 754/854. This alpha version is distributed * for testing purpose. Those who use this software * should report any bugs to * * fdlibm-comments@sunpro.eng.sun.com * * -- K.C. Ng, Oct 12, 1992 * ************************************************ */ /* double j0(double x), y0(double x) * Bessel function of the first and second kinds of order zero. * Method -- j0(x): * 1. For tiny x, we use j0(x) = 1 - x^2/4 + x^4/64 - ... * 2. Reduce x to |x| since j0(x)=j0(-x), and * for x in (0,2) * j0(x) = 1-z/4+ z^2*R0/S0, where z = x*x; * (precision: |j0-1+z/4-z^2R0/S0 |<2**-63.67 ) * for x in (2,inf) * j0(x) = sqrt(2/(pi*x))*(p0(x)*cos(x0)-q0(x)*sin(x0)) * where x0 = x-pi/4. It is better to compute sin(x0),cos(x0) * as follow: * cos(x0) = cos(x)cos(pi/4)+sin(x)sin(pi/4) * = 1/sqrt(2) * (cos(x) + sin(x)) * sin(x0) = sin(x)cos(pi/4)-cos(x)sin(pi/4) * = 1/sqrt(2) * (sin(x) - cos(x)) * (To avoid cancellation, use * sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x)) * to compute the worse one.) * * 3 Special cases * j0(nan)= nan * j0(0) = 1 * j0(inf) = 0 * * Method -- y0(x): * 1. For x<2. * Since * y0(x) = 2/pi*(j0(x)*(ln(x/2)+Euler) + x^2/4 - ...) * therefore y0(x)-2/pi*j0(x)*ln(x) is an even function. * We use the following function to approximate y0, * y0(x) = U(z)/V(z) + (2/pi)*(j0(x)*ln(x)), z= x^2 * where * U(z) = u0 + u1*z + ... + u6*z^6 * V(z) = 1 + v1*z + ... + v4*z^4 * with absolute approximation error bounded by 2**-72. * Note: For tiny x, U/V = u0 and j0(x)~1, hence * y0(tiny) = u0 + (2/pi)*ln(tiny), (choose tiny<2**-27) * 2. For x>=2. * y0(x) = sqrt(2/(pi*x))*(p0(x)*cos(x0)+q0(x)*sin(x0)) * where x0 = x-pi/4. It is better to compute sin(x0),cos(x0) * by the method mentioned above. * 3. Special cases: y0(0)=-inf, y0(x<0)=NaN, y0(inf)=0. */ #include #include #include #if defined(__vax__) || defined(tahoe) #define _IEEE 0 #else #define _IEEE 1 #define infnan(x) (0.0) #endif static double pzero(double), qzero(double); static double huge = 1e300, zero = 0.0, one = 1.0, invsqrtpi= 5.641895835477562869480794515607725858441e-0001, tpi = 0.636619772367581343075535053490057448, /* R0/S0 on [0, 2.00] */ r02 = 1.562499999999999408594634421055018003102e-0002, r03 = -1.899792942388547334476601771991800712355e-0004, r04 = 1.829540495327006565964161150603950916854e-0006, r05 = -4.618326885321032060803075217804816988758e-0009, s01 = 1.561910294648900170180789369288114642057e-0002, s02 = 1.169267846633374484918570613449245536323e-0004, s03 = 5.135465502073181376284426245689510134134e-0007, s04 = 1.166140033337900097836930825478674320464e-0009; double j0(x) double x; { double z, s,c,ss,cc,r,u,v; if (!finite(x)) if (_IEEE) return one/(x*x); else return (0); x = fabs(x); if (x >= 2.0) { /* |x| >= 2.0 */ s = sin(x); c = cos(x); ss = s-c; cc = s+c; if (x < .5 * DBL_MAX) { /* make sure x+x not overflow */ z = -cos(x+x); if ((s*c) 6.80564733841876927e+38) /* 2^129 */ z = (invsqrtpi*cc)/sqrt(x); else { u = pzero(x); v = qzero(x); z = invsqrtpi*(u*cc-v*ss)/sqrt(x); } return z; } if (x < 1.220703125e-004) { /* |x| < 2**-13 */ if (huge+x > one) { /* raise inexact if x != 0 */ if (x < 7.450580596923828125e-009) /* |x|<2**-27 */ return one; else return (one - 0.25*x*x); } } z = x*x; r = z*(r02+z*(r03+z*(r04+z*r05))); s = one+z*(s01+z*(s02+z*(s03+z*s04))); if (x < one) { /* |x| < 1.00 */ return (one + z*(-0.25+(r/s))); } else { u = 0.5*x; return ((one+u)*(one-u)+z*(r/s)); } } static double u00 = -7.380429510868722527422411862872999615628e-0002, u01 = 1.766664525091811069896442906220827182707e-0001, u02 = -1.381856719455968955440002438182885835344e-0002, u03 = 3.474534320936836562092566861515617053954e-0004, u04 = -3.814070537243641752631729276103284491172e-0006, u05 = 1.955901370350229170025509706510038090009e-0008, u06 = -3.982051941321034108350630097330144576337e-0011, v01 = 1.273048348341237002944554656529224780561e-0002, v02 = 7.600686273503532807462101309675806839635e-0005, v03 = 2.591508518404578033173189144579208685163e-0007, v04 = 4.411103113326754838596529339004302243157e-0010; double y0(x) double x; { double z, s, c, ss, cc, u, v; /* Y0(NaN) is NaN, y0(-inf) is Nan, y0(inf) is 0 */ if (!finite(x)) if (_IEEE) return (one/(x+x*x)); else return (0); if (x == 0) if (_IEEE) return (-one/zero); else return(infnan(-ERANGE)); if (x<0) if (_IEEE) return (zero/zero); else return (infnan(EDOM)); if (x >= 2.00) { /* |x| >= 2.0 */ /* y0(x) = sqrt(2/(pi*x))*(p0(x)*sin(x0)+q0(x)*cos(x0)) * where x0 = x-pi/4 * Better formula: * cos(x0) = cos(x)cos(pi/4)+sin(x)sin(pi/4) * = 1/sqrt(2) * (sin(x) + cos(x)) * sin(x0) = sin(x)cos(3pi/4)-cos(x)sin(3pi/4) * = 1/sqrt(2) * (sin(x) - cos(x)) * To avoid cancellation, use * sin(x) +- cos(x) = -cos(2x)/(sin(x) -+ cos(x)) * to compute the worse one. */ s = sin(x); c = cos(x); ss = s-c; cc = s+c; /* * j0(x) = 1/sqrt(pi) * (P(0,x)*cc - Q(0,x)*ss) / sqrt(x) * y0(x) = 1/sqrt(pi) * (P(0,x)*ss + Q(0,x)*cc) / sqrt(x) */ if (x < .5 * DBL_MAX) { /* make sure x+x not overflow */ z = -cos(x+x); if ((s*c) 6.80564733841876927e+38) /* > 2^129 */ z = (invsqrtpi*ss)/sqrt(x); else { u = pzero(x); v = qzero(x); z = invsqrtpi*(u*ss+v*cc)/sqrt(x); } return z; } if (x <= 7.450580596923828125e-009) { /* x < 2**-27 */ return (u00 + tpi*log(x)); } z = x*x; u = u00+z*(u01+z*(u02+z*(u03+z*(u04+z*(u05+z*u06))))); v = one+z*(v01+z*(v02+z*(v03+z*v04))); return (u/v + tpi*(j0(x)*log(x))); } /* The asymptotic expansions of pzero is * 1 - 9/128 s^2 + 11025/98304 s^4 - ..., where s = 1/x. * For x >= 2, We approximate pzero by * pzero(x) = 1 + (R/S) * where R = pr0 + pr1*s^2 + pr2*s^4 + ... + pr5*s^10 * S = 1 + ps0*s^2 + ... + ps4*s^10 * and * | pzero(x)-1-R/S | <= 2 ** ( -60.26) */ static double pr8[6] = { /* for x in [inf, 8]=1/[0,0.125] */ 0.0, -7.031249999999003994151563066182798210142e-0002, -8.081670412753498508883963849859423939871e+0000, -2.570631056797048755890526455854482662510e+0002, -2.485216410094288379417154382189125598962e+0003, -5.253043804907295692946647153614119665649e+0003, }; static double ps8[5] = { 1.165343646196681758075176077627332052048e+0002, 3.833744753641218451213253490882686307027e+0003, 4.059785726484725470626341023967186966531e+0004, 1.167529725643759169416844015694440325519e+0005, 4.762772841467309430100106254805711722972e+0004, }; static double pr5[6] = { /* for x in [8,4.5454]=1/[0.125,0.22001] */ -1.141254646918944974922813501362824060117e-0011, -7.031249408735992804117367183001996028304e-0002, -4.159610644705877925119684455252125760478e+0000, -6.767476522651671942610538094335912346253e+0001, -3.312312996491729755731871867397057689078e+0002, -3.464333883656048910814187305901796723256e+0002, }; static double ps5[5] = { 6.075393826923003305967637195319271932944e+0001, 1.051252305957045869801410979087427910437e+0003, 5.978970943338558182743915287887408780344e+0003, 9.625445143577745335793221135208591603029e+0003, 2.406058159229391070820491174867406875471e+0003, }; static double pr3[6] = {/* for x in [4.547,2.8571]=1/[0.2199,0.35001] */ -2.547046017719519317420607587742992297519e-0009, -7.031196163814817199050629727406231152464e-0002, -2.409032215495295917537157371488126555072e+0000, -2.196597747348830936268718293366935843223e+0001, -5.807917047017375458527187341817239891940e+0001, -3.144794705948885090518775074177485744176e+0001, }; static double ps3[5] = { 3.585603380552097167919946472266854507059e+0001, 3.615139830503038919981567245265266294189e+0002, 1.193607837921115243628631691509851364715e+0003, 1.127996798569074250675414186814529958010e+0003, 1.735809308133357510239737333055228118910e+0002, }; static double pr2[6] = {/* for x in [2.8570,2]=1/[0.3499,0.5] */ -8.875343330325263874525704514800809730145e-0008, -7.030309954836247756556445443331044338352e-0002, -1.450738467809529910662233622603401167409e+0000, -7.635696138235277739186371273434739292491e+0000, -1.119316688603567398846655082201614524650e+0001, -3.233645793513353260006821113608134669030e+0000, }; static double ps2[5] = { 2.222029975320888079364901247548798910952e+0001, 1.362067942182152109590340823043813120940e+0002, 2.704702786580835044524562897256790293238e+0002, 1.538753942083203315263554770476850028583e+0002, 1.465761769482561965099880599279699314477e+0001, }; static double pzero(x) double x; { double *p,*q,z,r,s; if (x >= 8.00) {p = pr8; q= ps8;} else if (x >= 4.54545211791992188) {p = pr5; q= ps5;} else if (x >= 2.85714149475097656) {p = pr3; q= ps3;} else if (x >= 2.00) {p = pr2; q= ps2;} z = one/(x*x); r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5])))); s = one+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*q[4])))); return one+ r/s; } /* For x >= 8, the asymptotic expansions of qzero is * -1/8 s + 75/1024 s^3 - ..., where s = 1/x. * We approximate pzero by * qzero(x) = s*(-1.25 + (R/S)) * where R = qr0 + qr1*s^2 + qr2*s^4 + ... + qr5*s^10 * S = 1 + qs0*s^2 + ... + qs5*s^12 * and * | qzero(x)/s +1.25-R/S | <= 2 ** ( -61.22) */ static double qr8[6] = { /* for x in [inf, 8]=1/[0,0.125] */ 0.0, 7.324218749999350414479738504551775297096e-0002, 1.176820646822526933903301695932765232456e+0001, 5.576733802564018422407734683549251364365e+0002, 8.859197207564685717547076568608235802317e+0003, 3.701462677768878501173055581933725704809e+0004, }; static double qs8[6] = { 1.637760268956898345680262381842235272369e+0002, 8.098344946564498460163123708054674227492e+0003, 1.425382914191204905277585267143216379136e+0005, 8.033092571195144136565231198526081387047e+0005, 8.405015798190605130722042369969184811488e+0005, -3.438992935378666373204500729736454421006e+0005, }; static double qr5[6] = { /* for x in [8,4.5454]=1/[0.125,0.22001] */ 1.840859635945155400568380711372759921179e-0011, 7.324217666126847411304688081129741939255e-0002, 5.835635089620569401157245917610984757296e+0000, 1.351115772864498375785526599119895942361e+0002, 1.027243765961641042977177679021711341529e+0003, 1.989977858646053872589042328678602481924e+0003, }; static double qs5[6] = { 8.277661022365377058749454444343415524509e+0001, 2.077814164213929827140178285401017305309e+0003, 1.884728877857180787101956800212453218179e+0004, 5.675111228949473657576693406600265778689e+0004, 3.597675384251145011342454247417399490174e+0004, -5.354342756019447546671440667961399442388e+0003, }; static double qr3[6] = {/* for x in [4.547,2.8571]=1/[0.2199,0.35001] */ 4.377410140897386263955149197672576223054e-0009, 7.324111800429115152536250525131924283018e-0002, 3.344231375161707158666412987337679317358e+0000, 4.262184407454126175974453269277100206290e+0001, 1.708080913405656078640701512007621675724e+0002, 1.667339486966511691019925923456050558293e+0002, }; static double qs3[6] = { 4.875887297245871932865584382810260676713e+0001, 7.096892210566060535416958362640184894280e+0002, 3.704148226201113687434290319905207398682e+0003, 6.460425167525689088321109036469797462086e+0003, 2.516333689203689683999196167394889715078e+0003, -1.492474518361563818275130131510339371048e+0002, }; static double qr2[6] = {/* for x in [2.8570,2]=1/[0.3499,0.5] */ 1.504444448869832780257436041633206366087e-0007, 7.322342659630792930894554535717104926902e-0002, 1.998191740938159956838594407540292600331e+0000, 1.449560293478857407645853071687125850962e+0001, 3.166623175047815297062638132537957315395e+0001, 1.625270757109292688799540258329430963726e+0001, }; static double qs2[6] = { 3.036558483552191922522729838478169383969e+0001, 2.693481186080498724211751445725708524507e+0002, 8.447837575953201460013136756723746023736e+0002, 8.829358451124885811233995083187666981299e+0002, 2.126663885117988324180482985363624996652e+0002, -5.310954938826669402431816125780738924463e+0000, }; static double qzero(x) double x; { double *p,*q, s,r,z; if (x >= 8.00) {p = qr8; q= qs8;} else if (x >= 4.54545211791992188) {p = qr5; q= qs5;} else if (x >= 2.85714149475097656) {p = qr3; q= qs3;} else if (x >= 2.00) {p = qr2; q= qs2;} z = one/(x*x); r = p[0]+z*(p[1]+z*(p[2]+z*(p[3]+z*(p[4]+z*p[5])))); s = one+z*(q[0]+z*(q[1]+z*(q[2]+z*(q[3]+z*(q[4]+z*q[5]))))); return (-.125 + r/s)/x; }