! D02PUF Example Program Text ! Mark 24 Release. NAG Copyright 2012. Module d02pufe_mod ! D02PUF Example Program Module: ! Parameters and User-defined Routines ! .. Use Statements .. Use nag_library, Only: nag_wp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: liwsav = 130, n = 4, nin = 5, & nout = 6 Integer, Parameter :: lrwsav = 350 + 32*n Contains Subroutine f(t,n,y,yp,iuser,ruser) ! .. Scalar Arguments .. Real (Kind=nag_wp), Intent (In) :: t Integer, Intent (In) :: n ! .. Array Arguments .. Real (Kind=nag_wp), Intent (Inout) :: ruser(*) Real (Kind=nag_wp), Intent (In) :: y(n) Real (Kind=nag_wp), Intent (Out) :: yp(n) Integer, Intent (Inout) :: iuser(*) ! .. 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 d02pufe_mod Program d02pufe ! D02PUF Example Main Program ! .. Use Statements .. Use nag_library, Only: d02pef, d02pqf, d02ptf, d02puf, nag_wp Use d02pufe_mod, Only: f, liwsav, lrwsav, n, nin, nout ! .. Implicit None Statement .. Implicit None ! .. Local Scalars .. Real (Kind=nag_wp) :: errmax, hnext, hstart, tend, & terrmx, tgot, tol, tstart, & twant, waste Integer :: fevals, ifail, method, stepcost, & stepsok ! .. Local Arrays .. Real (Kind=nag_wp) :: rmserr(n), ruser(1), thresh(n), & ygot(n), yinit(n), ymax(n), & ypgot(n) Real (Kind=nag_wp), Allocatable :: rwsav(:) Integer :: iuser(1) Integer, Allocatable :: iwsav(:) ! .. Executable Statements .. Write (nout,*) 'D02PUF Example Program Results' Allocate (rwsav(lrwsav),iwsav(liwsav)) ! Set initial conditions and input for D02PQF ! Skip heading in data file Read (nin,*) Read (nin,*) method Read (nin,*) tstart, tend Read (nin,*) yinit(1:n) Read (nin,*) hstart, tol Read (nin,*) thresh(1:n) ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call d02pqf(n,tstart,tend,yinit,tol,thresh,method,hstart,iwsav,rwsav, & ifail) Write (nout,99999) tol Write (nout,99998) Write (nout,99997) tstart, yinit(1:n) twant = tend integ: Do ifail = -1 Call d02pef(f,n,twant,tgot,ygot,ypgot,ymax,iuser,ruser,iwsav,rwsav, & 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:n) ! Compute and print error estimates. ifail = 0 Call d02puf(n,rmserr,errmax,terrmx,iwsav,rwsav,ifail) Write (nout,99996) rmserr(1:n) Write (nout,99995) errmax, terrmx ifail = 0 Call d02ptf(fevals,stepcost,waste,stepsok,hnext,iwsav,rwsav,ifail) Write (nout,99994) fevals 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 d02pufe