diff options
Diffstat (limited to 'lib/libm/noieee_src/n_erf.c')
| -rw-r--r-- | lib/libm/noieee_src/n_erf.c | 17 |
1 files changed, 9 insertions, 8 deletions
diff --git a/lib/libm/noieee_src/n_erf.c b/lib/libm/noieee_src/n_erf.c index 38d301793a1..3281985a8d9 100644 --- a/lib/libm/noieee_src/n_erf.c +++ b/lib/libm/noieee_src/n_erf.c @@ -1,3 +1,4 @@ +/* $OpenBSD: n_erf.c,v 1.5 2008/06/12 22:43:36 martynas Exp $ */ /* $NetBSD: n_erf.c,v 1.1 1995/10/10 23:36:43 ragge Exp $ */ /*- * Copyright (c) 1992, 1993 @@ -68,13 +69,13 @@ static char sccsid[] = "@(#)erf.c 8.1 (Berkeley) 6/4/93"; * erfc(x) = 1 - erf(x) if x<=0.25 * = 0.5 + ((0.5-x)-x*P) if x in [0.25,0.84375] * where - * 2 2 4 20 + * 2 2 4 20 * P = P(x ) = (p0 + p1 * x + p2 * x + ... + p10 * x ) * is an approximation to (erf(x)-x)/x with precision * * -56.45 * | P - (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 + ....) @@ -96,7 +97,7 @@ static char sccsid[] = "@(#)erf.c 8.1 (Berkeley) 6/4/93"; * 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 + * where * P1(s) = degree 6 poly in s * Q1(s) = degree 6 poly in s * @@ -105,7 +106,7 @@ static char sccsid[] = "@(#)erf.c 8.1 (Berkeley) 6/4/93"; * erfc(x) = (1/x)exp(-x*x-(.5*log(pi) -.5z + R(z)/S(z)) * * Where z = 1/(x*x), R is degree 9, and S is degree 3; - * + * * 5. For x in [4,28] * erf(x) = 1.0 - tiny * erfc(x) = (1/x)exp(-x*x-(.5*log(pi)+eps + zP(z)) @@ -139,7 +140,7 @@ static char sccsid[] = "@(#)erf.c 8.1 (Berkeley) 6/4/93"; * * 7. Special cases: * erf(0) = 0, erf(inf) = 1, erf(-inf) = -1, - * erfc(0) = 1, erfc(inf) = 0, erfc(-inf) = 2, + * erfc(0) = 1, erfc(inf) = 0, erfc(-inf) = 2, * erfc/erf(NaN) is NaN */ @@ -181,7 +182,7 @@ p8 = 1.640186161764254363152286358441771740838e-0006, p9 = -1.571599331700515057841960987689515895479e-0007, p10= 1.073087585213621540635426191486561494058e-0008; /* - * Coefficients for approximation to erf in [0.84375,1.25] + * Coefficients for approximation to erf in [0.84375,1.25] */ static double pa0 = -2.362118560752659485957248365514511540287e-0003, @@ -319,7 +320,7 @@ double erf(x) return (z-one); } -double erfc(x) +double erfc(x) double x; { double R, S, P, Q, s, ax, y, z, r; @@ -352,7 +353,7 @@ double erfc(x) P = pa0+s*(pa1+s*(pa2+s*(pa3+s*(pa4+s*(pa5+s*pa6))))); Q = one+s*(qa1+s*(qa2+s*(qa3+s*(qa4+s*(qa5+s*qa6))))); if (x>=0) { - z = one-c; return z - P/Q; + z = one-c; return z - P/Q; } else { z = c+P/Q; return one+z; } |