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/* mathews/simpson.f -- translated by f2c (version 20050501).
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
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "v3p_netlib.h"
/* NUMERICAL METHODS: FORTRAN Programs, (c) John H. Mathews 1994 */
/* To accompany the text: */
/* NUMERICAL METHODS for Mathematics, Science and Engineering, 2nd Ed, 1992 */
/* Prentice Hall, Englewood Cliffs, New Jersey, 07632, U.S.A. */
/* This free software is complements of the author. */
/* Algorithm 7.2 (Composite Simpson Rule). */
/* Section 7.2, Composite Trapezoidal and Simpson's Rule, Page 365 */
/* comment added by Kongbin Kang */
/* F: integrand function */
/* A: lower integration limit */
/* B: higher integration limit */
/* M: number of intervals. Notice, the subintervals used is 2M */
/* Srule: output parameter to store simpson rule result */
/*< SUBROUTINE SIMPRU(F,A,B,M,Srule) >*/
/* Subroutine */ int simpru_(doublereal (*f)(doublereal*),
doublereal *a, doublereal *b, integer *m,
doublereal *srule)
{
/* System generated locals */
integer i__1;
/* Local variables */
doublereal h__;
integer k;
doublereal x, sum, sumodd, sumeven;
/*< INTEGER K,M >*/
/*< DOUBLE PRECISION A,B,H,Sum,SumEven,SumOdd,Srule,X >*/
/*< EXTERNAL F >*/
/*< H=(B-A)/(2*M) >*/
h__ = (*b - *a) / (*m << 1);
/*< SumEven=0 >*/
sumeven = 0.;
/*< DO K=1,(M-1) >*/
i__1 = *m - 1;
for (k = 1; k <= i__1; ++k) {
/*< X=A+H*2*K >*/
x = *a + h__ * 2 * k;
/*< SumEven=SumEven+F(X) >*/
sumeven += (*f)(&x);
/*< ENDDO >*/
}
/*< SumOdd=0 >*/
sumodd = 0.;
/*< DO K=1,M >*/
i__1 = *m;
for (k = 1; k <= i__1; ++k) {
/*< X=A+H*(2*K-1) >*/
x = *a + h__ * ((k << 1) - 1);
/*< SumOdd=SumOdd+F(X) >*/
sumodd += (*f)(&x);
/*< ENDDO >*/
}
/*< Sum=H*(F(A)+F(B)+2*SumEven+4*SumOdd)/3 >*/
sum = h__ * ((*f)(a) + (*f)(b) + sumeven * 2 + sumodd * 4) / 3;
/*< Srule=Sum >*/
*srule = sum;
/*< RETURN >*/
return 0;
/*< END >*/
} /* simpru_ */
/*< SUBROUTINE XSIMPRU(F,A,B,M,Srule) >*/
/* Subroutine */ int xsimpru_(doublereal (*f)(doublereal*),
doublereal *a, doublereal *b, integer *
m, doublereal *srule)
{
/* System generated locals */
integer i__1;
/* Local variables */
doublereal h__;
integer k;
doublereal x, sum, sumodd, sumeven;
/* This subroutine uses labeled DO loop(s). */
/*< INTEGER K,M >*/
/*< DOUBLE PRECISION A,B,H,Sum,SumEven,SumOdd,Srule,X >*/
/*< EXTERNAL F >*/
/*< H=(B-A)/(2*M) >*/
h__ = (*b - *a) / (*m << 1);
/*< SumEven=0 >*/
sumeven = 0.;
/*< DO 10 K=1,(M-1) >*/
i__1 = *m - 1;
for (k = 1; k <= i__1; ++k) {
/*< X=A+H*2*K >*/
x = *a + h__ * 2 * k;
/*< SumEven=SumEven+F(X) >*/
sumeven += (*f)(&x);
/*< 10 CONTINUE >*/
/* L10: */
}
/*< SumOdd=0 >*/
sumodd = 0.;
/*< DO 20 K=1,M >*/
i__1 = *m;
for (k = 1; k <= i__1; ++k) {
/*< X=A+H*(2*K-1) >*/
x = *a + h__ * ((k << 1) - 1);
/*< SumOdd=SumOdd+F(X) >*/
sumodd += (*f)(&x);
/*< 20 CONTINUE >*/
/* L20: */
}
/*< Sum=H*(F(A)+F(B)+2*SumEven+4*SumOdd)/3 >*/
sum = h__ * ((*f)(a) + (*f)(b) + sumeven * 2 + sumodd * 4) / 3;
/*< Srule=Sum >*/
*srule = sum;
/*< RETURN >*/
return 0;
/*< END >*/
} /* xsimpru_ */
#ifdef __cplusplus
}
#endif
|
