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/* d9lgic.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__1 = 1;
static integer c__2 = 2;
/* DECK D9LGIC */
doublereal d9lgic_(doublereal *a, doublereal *x, doublereal *alx)
{
/* Initialized data */
/* static */ doublereal eps = 0.;
/* System generated locals */
doublereal ret_val;
/* Builtin functions */
double log(doublereal);
/* Local variables */
integer k;
doublereal p, r__, s, t, fk, xma, xpa;
extern doublereal d1mach_(integer *);
extern /* Subroutine */ int xermsg_(char *, char *, char *, integer *,
integer *, ftnlen, ftnlen, ftnlen);
/* ***BEGIN PROLOGUE D9LGIC */
/* ***SUBSIDIARY */
/* ***PURPOSE Compute the log complementary incomplete Gamma function */
/* for large X and for A .LE. X. */
/* ***LIBRARY SLATEC (FNLIB) */
/* ***CATEGORY C7E */
/* ***TYPE DOUBLE PRECISION (R9LGIC-S, D9LGIC-D) */
/* ***KEYWORDS COMPLEMENTARY INCOMPLETE GAMMA FUNCTION, FNLIB, LARGE X, */
/* LOGARITHM, SPECIAL FUNCTIONS */
/* ***AUTHOR Fullerton, W., (LANL) */
/* ***DESCRIPTION */
/* Compute the log complementary incomplete gamma function for large X */
/* and for A .LE. X. */
/* ***REFERENCES (NONE) */
/* ***ROUTINES CALLED D1MACH, XERMSG */
/* ***REVISION HISTORY (YYMMDD) */
/* 770701 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) */
/* 900720 Routine changed from user-callable to subsidiary. (WRB) */
/* ***END PROLOGUE D9LGIC */
/* ***FIRST EXECUTABLE STATEMENT D9LGIC */
// d1mach has been made thread safe, so there is no need for the
// statics in determining eps
// if (eps == 0.) {
// eps = .5 * d1mach_(&c__3);
// }
eps = .5 * d1mach_(&c__3);
xpa = *x + 1. - *a;
xma = *x - 1. - *a;
r__ = 0.;
p = 1.;
s = p;
for (k = 1; k <= 300; ++k) {
fk = (doublereal) k;
t = fk * (*a - fk) * (r__ + 1.);
r__ = -t / ((xma + fk * 2.) * (xpa + fk * 2.) + t);
p = r__ * p;
s += p;
if (abs(p) < eps * s) {
goto L20;
}
/* L10: */
}
xermsg_("SLATEC", "D9LGIC", "NO CONVERGENCE IN 300 TERMS OF CONTINUED FR"
"ACTION", &c__1, &c__2, (ftnlen)6, (ftnlen)6, (ftnlen)49);
L20:
ret_val = *a * *alx - *x + log(s / xpa);
return ret_val;
} /* d9lgic_ */
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