! D01FDF Example Program Text ! Mark 23 Release. NAG Copyright 2011. MODULE d01fdfe_mod ! D01FDF Example Program Module: ! Parameters and User-defined Routines ! .. Use Statements .. USE nag_library, ONLY : nag_wp ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nout = 6 CONTAINS FUNCTION f(ndim,x) ! .. Implicit None Statement .. IMPLICIT NONE ! .. Function Return Value .. REAL (KIND=nag_wp) :: f ! .. Scalar Arguments .. INTEGER, INTENT (IN) :: ndim ! .. Array Arguments .. REAL (KIND=nag_wp), INTENT (IN) :: x(ndim) ! .. Intrinsic Functions .. INTRINSIC abs, sqrt, sum ! .. Executable Statements .. f = 1.0E0_nag_wp/sqrt(abs(2.25E0_nag_wp-sum(x(1:ndim)**2))) RETURN END FUNCTION f SUBROUTINE region(ndim,x,j,c,d) ! .. Implicit None Statement .. IMPLICIT NONE ! .. Scalar Arguments .. REAL (KIND=nag_wp), INTENT (OUT) :: c, d INTEGER, INTENT (IN) :: j, ndim ! .. Array Arguments .. REAL (KIND=nag_wp), INTENT (IN) :: x(ndim) ! .. Intrinsic Functions .. INTRINSIC abs, sqrt, sum ! .. Executable Statements .. IF (j>1) THEN d = sqrt(abs(2.25E0_nag_wp-sum(x(1:(j-1))**2))) c = -d ELSE c = -1.5E0_nag_wp d = 1.5E0_nag_wp END IF RETURN END SUBROUTINE region END MODULE d01fdfe_mod PROGRAM d01fdfe ! D01FDF Example Main Program ! .. Use Statements .. USE nag_library, ONLY : d01fdf, d01fdv, nag_wp USE d01fdfe_mod, ONLY : f, nout, region ! .. Implicit None Statement .. IMPLICIT NONE ! .. Local Scalars .. REAL (KIND=nag_wp) :: r0, result, sigma, u INTEGER :: ifail, limit, ncalls, ndim ! .. Executable Statements .. WRITE (nout,*) 'D01FDF Example Program Results' ndim = 3 limit = 8000 u = 1.5E0_nag_wp sigma = 1.5E0_nag_wp r0 = 0.9E0_nag_wp ifail = 0 CALL d01fdf(ndim,f,sigma,d01fdv,limit,r0,u,result,ncalls,ifail) WRITE (nout,*) WRITE (nout,*) 'Sphere-to-sphere transformation' WRITE (nout,*) WRITE (nout,99999) 'Estimated value of the integral =', result WRITE (nout,99998) 'Number of integrand evaluations =', ncalls WRITE (nout,*) WRITE (nout,*) 'Product region transformation' sigma = -1.0E0_nag_wp r0 = 0.8E0_nag_wp ifail = 0 CALL d01fdf(ndim,f,sigma,region,limit,r0,u,result,ncalls,ifail) WRITE (nout,*) WRITE (nout,99999) 'Estimated value of the integral =', result WRITE (nout,99998) 'Number of integrand evaluations =', ncalls 99999 FORMAT (1X,A,F9.3) 99998 FORMAT (1X,A,I4) END PROGRAM d01fdfe