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Diffstat (limited to 'lib/mlibc/options/ansi/musl-generic-math/erf.c')
| -rw-r--r-- | lib/mlibc/options/ansi/musl-generic-math/erf.c | 273 |
1 files changed, 0 insertions, 273 deletions
diff --git a/lib/mlibc/options/ansi/musl-generic-math/erf.c b/lib/mlibc/options/ansi/musl-generic-math/erf.c deleted file mode 100644 index 2f30a29..0000000 --- a/lib/mlibc/options/ansi/musl-generic-math/erf.c +++ /dev/null @@ -1,273 +0,0 @@ -/* origin: FreeBSD /usr/src/lib/msun/src/s_erf.c */ -/* - * ==================================================== - * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. - * - * 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. - * ==================================================== - */ -/* double erf(double x) - * double erfc(double x) - * x - * 2 |\ - * erf(x) = --------- | exp(-t*t)dt - * sqrt(pi) \| - * 0 - * - * erfc(x) = 1-erf(x) - * Note that - * erf(-x) = -erf(x) - * erfc(-x) = 2 - erfc(x) - * - * Method: - * 1. For |x| in [0, 0.84375] - * erf(x) = x + x*R(x^2) - * erfc(x) = 1 - erf(x) if x in [-.84375,0.25] - * = 0.5 + ((0.5-x)-x*R) if x in [0.25,0.84375] - * where R = P/Q where P is an odd poly of degree 8 and - * Q is an odd poly of degree 10. - * -57.90 - * | R - (erf(x)-x)/x | <= 2 - * - * - * Remark. The formula is derived by noting - * erf(x) = (2/sqrt(pi))*(x - x^3/3 + x^5/10 - x^7/42 + ....) - * and that - * 2/sqrt(pi) = 1.128379167095512573896158903121545171688 - * is close to one. The interval is chosen because the fix - * point of erf(x) is near 0.6174 (i.e., erf(x)=x when x is - * near 0.6174), and by some experiment, 0.84375 is chosen to - * guarantee the error is less than one ulp for erf. - * - * 2. For |x| in [0.84375,1.25], let s = |x| - 1, and - * c = 0.84506291151 rounded to single (24 bits) - * erf(x) = sign(x) * (c + P1(s)/Q1(s)) - * erfc(x) = (1-c) - P1(s)/Q1(s) if x > 0 - * 1+(c+P1(s)/Q1(s)) if x < 0 - * |P1/Q1 - (erf(|x|)-c)| <= 2**-59.06 - * Remark: here we use the taylor series expansion at x=1. - * erf(1+s) = erf(1) + s*Poly(s) - * = 0.845.. + P1(s)/Q1(s) - * That is, we use rational approximation to approximate - * erf(1+s) - (c = (single)0.84506291151) - * Note that |P1/Q1|< 0.078 for x in [0.84375,1.25] - * where - * P1(s) = degree 6 poly in s - * Q1(s) = degree 6 poly in s - * - * 3. For x in [1.25,1/0.35(~2.857143)], - * erfc(x) = (1/x)*exp(-x*x-0.5625+R1/S1) - * erf(x) = 1 - erfc(x) - * where - * R1(z) = degree 7 poly in z, (z=1/x^2) - * S1(z) = degree 8 poly in z - * - * 4. For x in [1/0.35,28] - * erfc(x) = (1/x)*exp(-x*x-0.5625+R2/S2) if x > 0 - * = 2.0 - (1/x)*exp(-x*x-0.5625+R2/S2) if -6<x<0 - * = 2.0 - tiny (if x <= -6) - * erf(x) = sign(x)*(1.0 - erfc(x)) if x < 6, else - * erf(x) = sign(x)*(1.0 - tiny) - * where - * R2(z) = degree 6 poly in z, (z=1/x^2) - * S2(z) = degree 7 poly in z - * - * Note1: - * To compute exp(-x*x-0.5625+R/S), let s be a single - * precision number and s := x; then - * -x*x = -s*s + (s-x)*(s+x) - * exp(-x*x-0.5626+R/S) = - * exp(-s*s-0.5625)*exp((s-x)*(s+x)+R/S); - * Note2: - * Here 4 and 5 make use of the asymptotic series - * exp(-x*x) - * erfc(x) ~ ---------- * ( 1 + Poly(1/x^2) ) - * x*sqrt(pi) - * We use rational approximation to approximate - * g(s)=f(1/x^2) = log(erfc(x)*x) - x*x + 0.5625 - * Here is the error bound for R1/S1 and R2/S2 - * |R1/S1 - f(x)| < 2**(-62.57) - * |R2/S2 - f(x)| < 2**(-61.52) - * - * 5. For inf > x >= 28 - * erf(x) = sign(x) *(1 - tiny) (raise inexact) - * erfc(x) = tiny*tiny (raise underflow) if x > 0 - * = 2 - tiny if x<0 - * - * 7. Special case: - * erf(0) = 0, erf(inf) = 1, erf(-inf) = -1, - * erfc(0) = 1, erfc(inf) = 0, erfc(-inf) = 2, - * erfc/erf(NaN) is NaN - */ - -#include "libm.h" - -static const double -erx = 8.45062911510467529297e-01, /* 0x3FEB0AC1, 0x60000000 */ -/* - * Coefficients for approximation to erf on [0,0.84375] - */ -efx8 = 1.02703333676410069053e+00, /* 0x3FF06EBA, 0x8214DB69 */ -pp0 = 1.28379167095512558561e-01, /* 0x3FC06EBA, 0x8214DB68 */ -pp1 = -3.25042107247001499370e-01, /* 0xBFD4CD7D, 0x691CB913 */ -pp2 = -2.84817495755985104766e-02, /* 0xBF9D2A51, 0xDBD7194F */ -pp3 = -5.77027029648944159157e-03, /* 0xBF77A291, 0x236668E4 */ -pp4 = -2.37630166566501626084e-05, /* 0xBEF8EAD6, 0x120016AC */ -qq1 = 3.97917223959155352819e-01, /* 0x3FD97779, 0xCDDADC09 */ -qq2 = 6.50222499887672944485e-02, /* 0x3FB0A54C, 0x5536CEBA */ -qq3 = 5.08130628187576562776e-03, /* 0x3F74D022, 0xC4D36B0F */ -qq4 = 1.32494738004321644526e-04, /* 0x3F215DC9, 0x221C1A10 */ -qq5 = -3.96022827877536812320e-06, /* 0xBED09C43, 0x42A26120 */ -/* - * Coefficients for approximation to erf in [0.84375,1.25] - */ -pa0 = -2.36211856075265944077e-03, /* 0xBF6359B8, 0xBEF77538 */ -pa1 = 4.14856118683748331666e-01, /* 0x3FDA8D00, 0xAD92B34D */ -pa2 = -3.72207876035701323847e-01, /* 0xBFD7D240, 0xFBB8C3F1 */ -pa3 = 3.18346619901161753674e-01, /* 0x3FD45FCA, 0x805120E4 */ -pa4 = -1.10894694282396677476e-01, /* 0xBFBC6398, 0x3D3E28EC */ -pa5 = 3.54783043256182359371e-02, /* 0x3FA22A36, 0x599795EB */ -pa6 = -2.16637559486879084300e-03, /* 0xBF61BF38, 0x0A96073F */ -qa1 = 1.06420880400844228286e-01, /* 0x3FBB3E66, 0x18EEE323 */ -qa2 = 5.40397917702171048937e-01, /* 0x3FE14AF0, 0x92EB6F33 */ -qa3 = 7.18286544141962662868e-02, /* 0x3FB2635C, 0xD99FE9A7 */ -qa4 = 1.26171219808761642112e-01, /* 0x3FC02660, 0xE763351F */ -qa5 = 1.36370839120290507362e-02, /* 0x3F8BEDC2, 0x6B51DD1C */ -qa6 = 1.19844998467991074170e-02, /* 0x3F888B54, 0x5735151D */ -/* - * Coefficients for approximation to erfc in [1.25,1/0.35] - */ -ra0 = -9.86494403484714822705e-03, /* 0xBF843412, 0x600D6435 */ -ra1 = -6.93858572707181764372e-01, /* 0xBFE63416, 0xE4BA7360 */ -ra2 = -1.05586262253232909814e+01, /* 0xC0251E04, 0x41B0E726 */ -ra3 = -6.23753324503260060396e+01, /* 0xC04F300A, 0xE4CBA38D */ -ra4 = -1.62396669462573470355e+02, /* 0xC0644CB1, 0x84282266 */ -ra5 = -1.84605092906711035994e+02, /* 0xC067135C, 0xEBCCABB2 */ -ra6 = -8.12874355063065934246e+01, /* 0xC0545265, 0x57E4D2F2 */ -ra7 = -9.81432934416914548592e+00, /* 0xC023A0EF, 0xC69AC25C */ -sa1 = 1.96512716674392571292e+01, /* 0x4033A6B9, 0xBD707687 */ -sa2 = 1.37657754143519042600e+02, /* 0x4061350C, 0x526AE721 */ -sa3 = 4.34565877475229228821e+02, /* 0x407B290D, 0xD58A1A71 */ -sa4 = 6.45387271733267880336e+02, /* 0x40842B19, 0x21EC2868 */ -sa5 = 4.29008140027567833386e+02, /* 0x407AD021, 0x57700314 */ -sa6 = 1.08635005541779435134e+02, /* 0x405B28A3, 0xEE48AE2C */ -sa7 = 6.57024977031928170135e+00, /* 0x401A47EF, 0x8E484A93 */ -sa8 = -6.04244152148580987438e-02, /* 0xBFAEEFF2, 0xEE749A62 */ -/* - * Coefficients for approximation to erfc in [1/.35,28] - */ -rb0 = -9.86494292470009928597e-03, /* 0xBF843412, 0x39E86F4A */ -rb1 = -7.99283237680523006574e-01, /* 0xBFE993BA, 0x70C285DE */ -rb2 = -1.77579549177547519889e+01, /* 0xC031C209, 0x555F995A */ -rb3 = -1.60636384855821916062e+02, /* 0xC064145D, 0x43C5ED98 */ -rb4 = -6.37566443368389627722e+02, /* 0xC083EC88, 0x1375F228 */ -rb5 = -1.02509513161107724954e+03, /* 0xC0900461, 0x6A2E5992 */ -rb6 = -4.83519191608651397019e+02, /* 0xC07E384E, 0x9BDC383F */ -sb1 = 3.03380607434824582924e+01, /* 0x403E568B, 0x261D5190 */ -sb2 = 3.25792512996573918826e+02, /* 0x40745CAE, 0x221B9F0A */ -sb3 = 1.53672958608443695994e+03, /* 0x409802EB, 0x189D5118 */ -sb4 = 3.19985821950859553908e+03, /* 0x40A8FFB7, 0x688C246A */ -sb5 = 2.55305040643316442583e+03, /* 0x40A3F219, 0xCEDF3BE6 */ -sb6 = 4.74528541206955367215e+02, /* 0x407DA874, 0xE79FE763 */ -sb7 = -2.24409524465858183362e+01; /* 0xC03670E2, 0x42712D62 */ - -static double erfc1(double x) -{ - double_t s,P,Q; - - s = fabs(x) - 1; - P = pa0+s*(pa1+s*(pa2+s*(pa3+s*(pa4+s*(pa5+s*pa6))))); - Q = 1+s*(qa1+s*(qa2+s*(qa3+s*(qa4+s*(qa5+s*qa6))))); - return 1 - erx - P/Q; -} - -static double erfc2(uint32_t ix, double x) -{ - double_t s,R,S; - double z; - - if (ix < 0x3ff40000) /* |x| < 1.25 */ - return erfc1(x); - - x = fabs(x); - s = 1/(x*x); - if (ix < 0x4006db6d) { /* |x| < 1/.35 ~ 2.85714 */ - R = ra0+s*(ra1+s*(ra2+s*(ra3+s*(ra4+s*( - ra5+s*(ra6+s*ra7)))))); - S = 1.0+s*(sa1+s*(sa2+s*(sa3+s*(sa4+s*( - sa5+s*(sa6+s*(sa7+s*sa8))))))); - } else { /* |x| > 1/.35 */ - R = rb0+s*(rb1+s*(rb2+s*(rb3+s*(rb4+s*( - rb5+s*rb6))))); - S = 1.0+s*(sb1+s*(sb2+s*(sb3+s*(sb4+s*( - sb5+s*(sb6+s*sb7)))))); - } - z = x; - SET_LOW_WORD(z,0); - return exp(-z*z-0.5625)*exp((z-x)*(z+x)+R/S)/x; -} - -double erf(double x) -{ - double r,s,z,y; - uint32_t ix; - int sign; - - GET_HIGH_WORD(ix, x); - sign = ix>>31; - ix &= 0x7fffffff; - if (ix >= 0x7ff00000) { - /* erf(nan)=nan, erf(+-inf)=+-1 */ - return 1-2*sign + 1/x; - } - if (ix < 0x3feb0000) { /* |x| < 0.84375 */ - if (ix < 0x3e300000) { /* |x| < 2**-28 */ - /* avoid underflow */ - return 0.125*(8*x + efx8*x); - } - z = x*x; - r = pp0+z*(pp1+z*(pp2+z*(pp3+z*pp4))); - s = 1.0+z*(qq1+z*(qq2+z*(qq3+z*(qq4+z*qq5)))); - y = r/s; - return x + x*y; - } - if (ix < 0x40180000) /* 0.84375 <= |x| < 6 */ - y = 1 - erfc2(ix,x); - else - y = 1 - 0x1p-1022; - return sign ? -y : y; -} - -double erfc(double x) -{ - double r,s,z,y; - uint32_t ix; - int sign; - - GET_HIGH_WORD(ix, x); - sign = ix>>31; - ix &= 0x7fffffff; - if (ix >= 0x7ff00000) { - /* erfc(nan)=nan, erfc(+-inf)=0,2 */ - return 2*sign + 1/x; - } - if (ix < 0x3feb0000) { /* |x| < 0.84375 */ - if (ix < 0x3c700000) /* |x| < 2**-56 */ - return 1.0 - x; - z = x*x; - r = pp0+z*(pp1+z*(pp2+z*(pp3+z*pp4))); - s = 1.0+z*(qq1+z*(qq2+z*(qq3+z*(qq4+z*qq5)))); - y = r/s; - if (sign || ix < 0x3fd00000) { /* x < 1/4 */ - return 1.0 - (x+x*y); - } - return 0.5 - (x - 0.5 + x*y); - } - if (ix < 0x403c0000) { /* 0.84375 <= |x| < 28 */ - return sign ? 2 - erfc2(ix,x) : erfc2(ix,x); - } - return sign ? 2 - 0x1p-1022 : 0x1p-1022*0x1p-1022; -} |