! D02PEF Example Program Text
! Mark 26.1 Release. NAG Copyright 2016.
Module d02pefe_mod
! D02PEF Example Program Module:
! Parameters and User-defined Routines
! .. Use Statements ..
Use nag_library, Only: nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Accessibility Statements ..
Private
Public :: f
! .. Parameters ..
Real (Kind=nag_wp), Parameter, Public :: tol0 = 1.0E-3_nag_wp
Integer, Parameter, Public :: liwsav = 130, n = 2, nin = 5, &
nout = 6, npts = 8
Integer, Parameter, Public :: 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(*)
! .. Executable Statements ..
yp(1) = y(2)
yp(2) = -y(1)
Return
End Subroutine f
End Module d02pefe_mod
Program d02pefe
! D02PEF Example Main Program
! .. Use Statements ..
Use d02pefe_mod, Only: f, liwsav, lrwsav, n, nin, nout, npts, tol0
Use nag_library, Only: d02pef, d02pqf, d02ptf, nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Local Scalars ..
Real (Kind=nag_wp) :: hnext, hstart, tend, tgot, tinc, &
tol, tstart, twant, waste
Integer :: fevals, i, ifail, j, method, &
stepcost, stepsok
! .. Local Arrays ..
Real (Kind=nag_wp) :: ruser(1), thresh(n), ygot(n), &
yinit(n), ymax(n), ypgot(n)
Real (Kind=nag_wp), Allocatable :: rwsav(:)
Integer :: iuser(1)
Integer, Allocatable :: iwsav(:)
! .. Intrinsic Procedures ..
Intrinsic :: real
! .. Executable Statements ..
Write (nout,*) 'D02PEF Example Program Results'
Allocate (iwsav(liwsav),rwsav(lrwsav))
! 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
Read (nin,*) thresh(1:n)
! Set control for output
tinc = (tend-tstart)/real(npts,kind=nag_wp)
tol = 10.0_nag_wp*tol0
loop: Do i = 1, 2
tol = tol*0.1_nag_wp
! 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 = tstart
Do j = 1, npts
twant = twant + tinc
ifail = 0
Call d02pef(f,n,twant,tgot,ygot,ypgot,ymax,iuser,ruser,iwsav,rwsav, &
ifail)
Write (nout,99997) tgot, ygot(1:n)
End Do
ifail = 0
Call d02ptf(fevals,stepcost,waste,stepsok,hnext,iwsav,rwsav,ifail)
Write (nout,99996) fevals
End Do loop
99999 Format (/,' Calculation with TOL = ',1P,E8.1)
99998 Format (/,' t y1 y2',/)
99997 Format (1X,F6.3,2(3X,F7.3))
99996 Format (/,' Cost of the integration in evaluations of F is',I6)
End Program d02pefe