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/* dlnrel.f -- translated by f2c (version 20041007).
You must link the resulting object file with libf2c:
on Microsoft Windows system, link with libf2c.lib;
on Linux or Unix systems, link with .../path/to/libf2c.a -lm
or, if you install libf2c.a in a standard place, with -lf2c -lm
-- in that order, at the end of the command line, as in
cc *.o -lf2c -lm
Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
http://www.netlib.org/f2c/libf2c.zip
*/
/** This routine has been editted to be thread safe **/
#define V3P_NETLIB_SRC
#include "v3p_netlib.h"
/* Table of constant values */
static integer c__3 = 3;
static integer c__43 = 43;
static integer c__4 = 4;
static integer c__2 = 2;
static integer c__1 = 1;
/* DECK DLNREL */
doublereal dlnrel_(doublereal *x)
{
/* Initialized data */
static doublereal alnrcs[43] = { 1.0378693562743769800686267719098,
-.13364301504908918098766041553133,
.01940824913552056335792619937475,
-.0030107551127535777690376537776592,
4.8694614797154850090456366509137e-4,
-8.1054881893175356066809943008622e-5,
1.3778847799559524782938251496059e-5,
-2.3802210894358970251369992914935e-6,
4.1640416213865183476391859901989e-7,
-7.3595828378075994984266837031998e-8,
1.3117611876241674949152294345011e-8,
-2.3546709317742425136696092330175e-9,
4.2522773276034997775638052962567e-10,
-7.71908941348407968261081074933e-11,
1.4075746481359069909215356472191e-11,
-2.5769072058024680627537078627584e-12,
4.7342406666294421849154395005938e-13,
-8.7249012674742641745301263292675e-14,
1.6124614902740551465739833119115e-14,
-2.9875652015665773006710792416815e-15,
5.5480701209082887983041321697279e-16,
-1.0324619158271569595141333961932e-16,
1.9250239203049851177878503244868e-17,
-3.5955073465265150011189707844266e-18,
6.7264542537876857892194574226773e-19,
-1.2602624168735219252082425637546e-19,
2.3644884408606210044916158955519e-20,
-4.4419377050807936898878389179733e-21,
8.3546594464034259016241293994666e-22,
-1.5731559416479562574899253521066e-22,
2.9653128740247422686154369706666e-23,
-5.5949583481815947292156013226666e-24,
1.0566354268835681048187284138666e-24,
-1.9972483680670204548314999466666e-25,
3.7782977818839361421049855999999e-26,
-7.1531586889081740345038165333333e-27,
1.3552488463674213646502024533333e-27,
-2.5694673048487567430079829333333e-28,
4.8747756066216949076459519999999e-29,
-9.2542112530849715321132373333333e-30,
1.757859784176023923326976e-30,
-3.3410026677731010351377066666666e-31,
6.3533936180236187354180266666666e-32 };
// static logical first = TRUE_;
/* System generated locals */
real r__1;
doublereal ret_val = 0., d__1;
/* Builtin functions */
double sqrt(doublereal), log(doublereal);
/* Local variables */
/* static */ doublereal xmin;
extern doublereal d1mach_(integer *), dcsevl_(doublereal *, doublereal *,
integer *);
/* static */ integer nlnrel;
extern integer initds_(doublereal *, integer *, real *);
extern /* Subroutine */ int xermsg_(char *, char *, char *, integer *,
integer *, ftnlen, ftnlen, ftnlen);
/* ***BEGIN PROLOGUE DLNREL */
/* ***PURPOSE Evaluate ln(1+X) accurate in the sense of relative error. */
/* ***LIBRARY SLATEC (FNLIB) */
/* ***CATEGORY C4B */
/* ***TYPE DOUBLE PRECISION (ALNREL-S, DLNREL-D, CLNREL-C) */
/* ***KEYWORDS ELEMENTARY FUNCTIONS, FNLIB, LOGARITHM */
/* ***AUTHOR Fullerton, W., (LANL) */
/* ***DESCRIPTION */
/* DLNREL(X) calculates the double precision natural logarithm of */
/* (1.0+X) for double precision argument X. This routine should */
/* be used when X is small and accurate to calculate the logarithm */
/* accurately (in the relative error sense) in the neighborhood */
/* of 1.0. */
/* Series for ALNR on the interval -3.75000E-01 to 3.75000E-01 */
/* with weighted error 6.35E-32 */
/* log weighted error 31.20 */
/* significant figures required 30.93 */
/* decimal places required 32.01 */
/* ***REFERENCES (NONE) */
/* ***ROUTINES CALLED D1MACH, DCSEVL, INITDS, XERMSG */
/* ***REVISION HISTORY (YYMMDD) */
/* 770601 DATE WRITTEN */
/* 890531 Changed all specific intrinsics to generic. (WRB) */
/* 890531 REVISION DATE from Version 3.2 */
/* 891214 Prologue converted to Version 4.0 format. (BAB) */
/* 900315 CALLs to XERROR changed to CALLs to XERMSG. (THJ) */
/* ***END PROLOGUE DLNREL */
/* ***FIRST EXECUTABLE STATEMENT DLNREL */
// d1mach has been made thread safe, so there is no need for the
// statics in determining these values
// if (first) {
// r__1 = (real) d1mach_(&c__3) * .1f;
// nlnrel = initds_(alnrcs, &c__43, &r__1);
// xmin = sqrt(d1mach_(&c__4)) - 1.;
// }
// first = FALSE_;
r__1 = (real) d1mach_(&c__3) * .1f;
nlnrel = initds_(alnrcs, &c__43, &r__1);
xmin = sqrt(d1mach_(&c__4)) - 1.;
if (*x <= -1.) {
xermsg_("SLATEC", "DLNREL", "X IS LE -1", &c__2, &c__2, (ftnlen)6, (
ftnlen)6, (ftnlen)10);
}
if (*x < xmin) {
xermsg_("SLATEC", "DLNREL", "ANSWER LT HALF PRECISION BECAUSE X TOO "
"NEAR -1", &c__1, &c__1, (ftnlen)6, (ftnlen)6, (ftnlen)46);
}
if (abs(*x) <= .375) {
d__1 = *x / .375;
ret_val = *x * (1. - *x * dcsevl_(&d__1, alnrcs, &nlnrel));
}
if (abs(*x) > .375) {
ret_val = log(*x + 1.);
}
return ret_val;
} /* dlnrel_ */
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