! D02PZF Example Program Text ! Mark 24 Release. NAG Copyright 2012. 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) ! .. 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 Procedures .. 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