! D03PRF Example Program Text ! Mark 24 Release. NAG Copyright 2012. Module d03prfe_mod ! D03PRF Example Program Module: ! Parameters and User-defined Routines ! .. Use Statements .. Use nag_library, Only: nag_wp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Real (Kind=nag_wp), Parameter :: half = 0.5_nag_wp Real (Kind=nag_wp), Parameter :: two = 2.0_nag_wp Integer, Parameter :: itrace = 0, ncode = 0, nin = 5, & nleft = 1, nout = 6, npde = 2, & nxfix = 0, nxi = 0 Contains Subroutine uvinit(npde,npts,nxi,x,xi,u,ncode,v) ! .. Use Statements .. Use nag_library, Only: x01aaf ! .. Scalar Arguments .. Integer, Intent (In) :: ncode, npde, npts, nxi ! .. Array Arguments .. Real (Kind=nag_wp), Intent (Out) :: u(npde,npts), v(ncode) Real (Kind=nag_wp), Intent (In) :: x(npts), xi(nxi) ! .. Local Scalars .. Real (Kind=nag_wp) :: pi Integer :: i ! .. Intrinsic Procedures .. Intrinsic :: exp, sin ! .. Executable Statements .. pi = x01aaf(pi) Do i = 1, npts u(1,i) = exp(x(i)) u(2,i) = x(i)**2 + sin(two*pi*x(i)**2) End Do Return End Subroutine uvinit Subroutine pdedef(npde,t,x,u,udot,ux,ncode,v,vdot,res,ires) ! .. Scalar Arguments .. Real (Kind=nag_wp), Intent (In) :: t, x Integer, Intent (Inout) :: ires Integer, Intent (In) :: ncode, npde ! .. Array Arguments .. Real (Kind=nag_wp), Intent (Out) :: res(npde) Real (Kind=nag_wp), Intent (In) :: u(npde), udot(npde), ux(npde), & v(ncode), vdot(ncode) ! .. Executable Statements .. If (ires==-1) Then res(1) = udot(1) res(2) = udot(2) Else res(1) = udot(1) + ux(1) + ux(2) res(2) = udot(2) + 4.0_nag_wp*ux(1) + ux(2) End If Return End Subroutine pdedef Subroutine bndary(npde,t,ibnd,nobc,u,udot,ncode,v,vdot,res,ires) ! .. Use Statements .. Use nag_library, Only: x01aaf ! .. Scalar Arguments .. Real (Kind=nag_wp), Intent (In) :: t Integer, Intent (In) :: ibnd, ncode, nobc, npde Integer, Intent (Inout) :: ires ! .. Array Arguments .. Real (Kind=nag_wp), Intent (Out) :: res(nobc) Real (Kind=nag_wp), Intent (In) :: u(npde), udot(npde), v(ncode), & vdot(ncode) ! .. Local Scalars .. Real (Kind=nag_wp) :: pp, ppt1, ppt3, t1, t3 ! .. Intrinsic Procedures .. Intrinsic :: exp, sin ! .. Executable Statements .. If (ires==-1) Then res(1) = 0.0_nag_wp Else pp = two*x01aaf(pp) t1 = t t3 = -3.0_nag_wp*t If (ibnd==0) Then ppt3 = sin(pp*t3**2) ppt1 = sin(pp*t1**2) res(1) = u(1) - half*(exp(t3)+exp(t1)+half*(ppt3-ppt1)) res(1) = res(1) - 2.0_nag_wp*t**2 Else t3 = t3 + 1.0_nag_wp t1 = t1 + 1.0_nag_wp ppt3 = sin(pp*t3**2) ppt1 = sin(pp*t1**2) res(1) = u(2) - (exp(t3)-exp(t1)+half*(ppt3+ppt1)) res(1) = res(1) - (1.0_nag_wp+5.0_nag_wp*t**2-2.0_nag_wp*t) End If End If Return End Subroutine bndary Subroutine monitf(t,npts,npde,x,u,fmon) ! .. Scalar Arguments .. Real (Kind=nag_wp), Intent (In) :: t Integer, Intent (In) :: npde, npts ! .. Array Arguments .. Real (Kind=nag_wp), Intent (Out) :: fmon(npts) Real (Kind=nag_wp), Intent (In) :: u(npde,npts), x(npts) ! .. Local Scalars .. Real (Kind=nag_wp) :: d2x1, d2x2, h1, h2, h3 Integer :: i ! .. Intrinsic Procedures .. Intrinsic :: abs, max ! .. Executable Statements .. Do i = 2, npts - 1 h1 = x(i) - x(i-1) h2 = x(i+1) - x(i) h3 = half*(x(i+1)-x(i-1)) ! Second derivatives .. d2x1 = abs(((u(1,i+1)-u(1,i))/h2-(u(1,i)-u(1,i-1))/h1)/h3) d2x2 = abs(((u(2,i+1)-u(2,i))/h2-(u(2,i)-u(2,i-1))/h1)/h3) fmon(i) = max(d2x1,d2x2) End Do fmon(1) = fmon(2) fmon(npts) = fmon(npts-1) Return End Subroutine monitf Subroutine exact(t,npde,npts,x,u) ! Exact solution (for comparison purposes) ! .. Use Statements .. Use nag_library, Only: x01aaf ! .. Scalar Arguments .. Real (Kind=nag_wp), Intent (In) :: t Integer, Intent (In) :: npde, npts ! .. Array Arguments .. Real (Kind=nag_wp), Intent (Out) :: u(npde,npts) Real (Kind=nag_wp), Intent (In) :: x(npts) ! .. Local Scalars .. Real (Kind=nag_wp) :: pp, ppt1, ppt3, x1, x3 Integer :: i ! .. Intrinsic Procedures .. Intrinsic :: exp, sin ! .. Executable Statements .. pp = 2.0_nag_wp*x01aaf(pp) Do i = 1, npts x1 = x(i) + t x3 = x(i) - 3.0_nag_wp*t ppt3 = sin(pp*x3**2) ppt1 = sin(pp*x1**2) u(1,i) = half*(exp(x3)+exp(x1)+half*(ppt3-ppt1)) - two*x(i)*t + & two*t**2 u(2,i) = (exp(x3)-exp(x1)+half*(ppt3+ppt1)) - two*x(i)*t + x(i)**2 + & 5.0_nag_wp*t**2 End Do Return End Subroutine exact End Module d03prfe_mod Program d03prfe ! D03PRF Example Main Program ! .. Use Statements .. Use nag_library, Only: d03pek, d03prf, d03pzf, nag_wp Use d03prfe_mod, Only: bndary, exact, itrace, monitf, ncode, nin, nleft, & nout, npde, nxfix, nxi, pdedef, uvinit ! .. Implicit None Statement .. Implicit None ! .. Local Scalars .. Real (Kind=nag_wp) :: con, dxmesh, tout, trmesh, ts, & xratio Integer :: i, ifail, ind, intpts, ipminf, & it, itask, itol, itype, lenode, & lisave, lrsave, neqn, npts, & nrmesh, nwkres Logical :: remesh, theta Character (1) :: laopt, norm ! .. Local Arrays .. Real (Kind=nag_wp) :: algopt(30), atol(1), rtol(1), & xfix(1), xi(1) Real (Kind=nag_wp), Allocatable :: rsave(:), u(:,:), ue(:,:), & uout(:,:,:), x(:), xout(:) Integer, Allocatable :: isave(:) ! .. Intrinsic Procedures .. Intrinsic :: real ! .. Executable Statements .. Write (nout,*) 'D03PRF Example Program Results' ! Skip heading in data file Read (nin,*) Read (nin,*) npts, intpts, itype lisave = 25 + nxfix neqn = npde*npts + ncode nwkres = npde*(npts+21+3*npde) + 7*npts + nxfix + 3 lenode = 11*neqn + 50 lrsave = neqn*neqn + neqn + nwkres + lenode Allocate (rsave(lrsave),u(npde,npts),ue(npde,npts), & uout(npde,intpts,itype),x(npts),xout(intpts),isave(lisave)) Read (nin,*) itol Read (nin,*) atol(1), rtol(1) ! Set remesh parameters remesh = .True. nrmesh = 3 dxmesh = 0.0_nag_wp con = 5.0_nag_wp/real(npts-1,kind=nag_wp) xratio = 1.2_nag_wp ipminf = 0 ! Initialise mesh Do i = 1, npts x(i) = real(i-1,kind=nag_wp)/real(npts-1,kind=nag_wp) End Do xi(1) = 0.0_nag_wp Read (nin,*) xout(1:intpts) Read (nin,*) norm, laopt ind = 0 itask = 1 ! Set theta to .TRUE. if the Theta integrator is required theta = .False. algopt(1:30) = 0.0_nag_wp If (theta) Then algopt(1) = 2.0_nag_wp algopt(6) = 2.0_nag_wp algopt(7) = 1.0_nag_wp End If ! Loop over output value of t ts = 0.0_nag_wp tout = 0.0_nag_wp Do it = 1, 5 tout = 0.05_nag_wp*real(it,kind=nag_wp) ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call d03prf(npde,ts,tout,pdedef,bndary,uvinit,u,npts,x,nleft,ncode, & d03pek,nxi,xi,neqn,rtol,atol,itol,norm,laopt,algopt,remesh,nxfix, & xfix,nrmesh,dxmesh,trmesh,ipminf,xratio,con,monitf,rsave,lrsave, & isave,lisave,itask,itrace,ind,ifail) If (it==1) Then Write (nout,99996) atol, npts Write (nout,99999) nrmesh Write (nout,99998) xout(1:intpts) End If ! Interpolate at output points .. ifail = 0 Call d03pzf(npde,0,u,npts,x,xout,intpts,itype,uout,ifail) ! Check against exact solution .. Call exact(ts,npde,intpts,xout,ue) Write (nout,99997) ts Write (nout,99994) uout(1,1:intpts,1) Write (nout,99993) ue(1,1:intpts) Write (nout,99992) uout(2,1:intpts,1) Write (nout,99991) ue(2,1:intpts) End Do Write (nout,99995) isave(1), isave(2), isave(3), isave(5) 99999 Format (' Remeshing every ',I3,' time steps'/) 99998 Format (' X ',5F10.4/) 99997 Format (' T = ',F6.3) 99996 Format (//' Accuracy requirement =',E10.3,' Number of points = ',I3/) 99995 Format (' Number of integration steps in time = ',I6/' Number o', & 'f function evaluations = ',I6/' Number of Jacobian eval','uations =', & I6/' Number of iterations = ',I6) 99994 Format (' Approx U1',5F10.4) 99993 Format (' Exact U1',5F10.4) 99992 Format (' Approx U2',5F10.4) 99991 Format (' Exact U2',5F10.4/) End Program d03prfe