! D02PZF Example Program Text ! Mark 23 Release. NAG Copyright 2011. MODULE d02pzfe_mod ! D02PZF Example Program Module: ! Parameters and User-defined Routines ! .. Use Statements .. USE nag_library, ONLY : nag_wp ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: neq = 4, nin = 5, nout = 6 INTEGER, PARAMETER :: lenwrk = 32*neq CONTAINS SUBROUTINE f(t,y,yp) ! .. Implicit None Statement .. IMPLICIT NONE ! .. Scalar Arguments .. REAL (KIND=nag_wp), INTENT (IN) :: t ! .. Array Arguments .. REAL (KIND=nag_wp), INTENT (IN) :: y(*) REAL (KIND=nag_wp), INTENT (OUT) :: yp(*) ! .. Local Scalars .. REAL (KIND=nag_wp) :: r ! .. Intrinsic Functions .. INTRINSIC sqrt ! .. Executable Statements .. r = sqrt(y(1)**2+y(2)**2) yp(1) = y(3) yp(2) = y(4) yp(3) = -y(1)/r**3 yp(4) = -y(2)/r**3 RETURN END SUBROUTINE f END MODULE d02pzfe_mod PROGRAM d02pzfe ! D02PZF Example Main Program ! .. Use Statements .. USE nag_library, ONLY : d02pcf, d02pvf, d02pyf, d02pzf, nag_wp USE d02pzfe_mod, ONLY : f, lenwrk, neq, nin, nout ! .. Implicit None Statement .. IMPLICIT NONE ! .. Local Scalars .. REAL (KIND=nag_wp) :: errmax, hnext, hstart, tend, & terrmx, tgot, tol, tstart, & twant, waste INTEGER :: ifail, method, stpcst, stpsok, & totf LOGICAL :: errass ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: rmserr(:), thres(:), work(:), & ygot(:), ymax(:), ypgot(:), & ystart(:) ! .. Executable Statements .. WRITE (nout,*) 'D02PZF Example Program Results' ! Skip heading in data file READ (nin,*) ! neq: number of differential equations READ (nin,*) method ALLOCATE (rmserr(neq),thres(neq),work(lenwrk),ygot(neq),ymax(neq), & ypgot(neq),ystart(neq)) ! Set initial conditions and input for D02PVF READ (nin,*) tstart, tend READ (nin,*) ystart(1:neq) READ (nin,*) hstart, tol READ (nin,*) thres(1:neq) READ (nin,*) errass ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 CALL d02pvf(neq,tstart,ystart,tend,tol,thres,method,'Usual Task', & errass,hstart,work,lenwrk,ifail) WRITE (nout,99999) tol WRITE (nout,99998) WRITE (nout,99997) tstart, ystart(1:neq) twant = tend INTEG: DO ifail = -1 CALL d02pcf(f,twant,tgot,ygot,ypgot,ymax,work,ifail) IF (ifail<2 .OR. ifail>4) THEN EXIT INTEG END IF END DO INTEG IF (ifail==0) THEN ! Print solution. WRITE (nout,99997) tgot, ygot(1:neq) ! Compute and print error estimates. ifail = 0 CALL d02pzf(rmserr,errmax,terrmx,work,ifail) WRITE (nout,99996) rmserr(1:neq) WRITE (nout,99995) errmax, terrmx ifail = 0 CALL d02pyf(totf,stpcst,waste,stpsok,hnext,ifail) WRITE (nout,99994) totf END IF 99999 FORMAT (/' Calculation with TOL = ',E8.1) 99998 FORMAT (/' t y1 y2 y3 y4'/) 99997 FORMAT (1X,F6.3,4(3X,F8.4)) 99996 FORMAT (/' Componentwise error assessment'/9X,4(2X,E9.2)) 99995 FORMAT (/' Worst global error observed was ',E9.2, & ' - it occurred at T = ',F6.3) 99994 FORMAT (/' Cost of the integration in evaluations of F is',I6) END PROGRAM d02pzfe