Program f11dxfe
! F11DXF Example Program Text
! Mark 25 Release. NAG Copyright 2014.
! .. Use Statements ..
Use nag_library, Only: f11brf, f11bsf, f11btf, f11dxf, f11xnf, nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Integer, Parameter :: nin = 5, nout = 6
! .. Local Scalars ..
Real (Kind=nag_wp) :: anorm, sigmax, stplhs, stprhs, tol
Integer :: i, ifail, ifail1, irevcm, iterm, &
itn, lwork, lwreq, m, maxitn, monit, &
n, niter, nnz
Character (1) :: init, norm, precon, weight
Character (8) :: method
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: a(:), b(:), diag(:), work(:), x(:)
Real (Kind=nag_wp), Allocatable :: wgt(:)
Integer, Allocatable :: icol(:), irow(:)
! .. Intrinsic Procedures ..
Intrinsic :: log, nint
! .. Executable Statements ..
Write (nout,*) 'F11DXF Example Program Results'
! Skip heading in data file
Read (nin,*)
Read (nin,*) n
Read (nin,*) nnz
lwork = 300
Allocate (a(nnz),b(n),diag(n),work(lwork),x(n),wgt(n),icol(nnz), &
irow(nnz))
! Read or initialize the parameters for the iterative solver
Read (nin,*) method
Read (nin,*) precon, norm, weight, iterm
Read (nin,*) m, tol, maxitn
Read (nin,*) monit
anorm = 0.0E0_nag_wp
sigmax = 0.0E0_nag_wp
! Read the parameters for the preconditioner
Read (nin,*) niter
! Read the non-zero elements of the matrix A
Do i = 1, nnz
Read (nin,*) a(i), irow(i), icol(i)
End Do
! Read right-hand side vector b and initial approximate solution
Read (nin,*) b(1:n)
Read (nin,*) x(1:n)
! Call F11BDF to initialize the solver
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call f11brf(method,precon,norm,weight,iterm,n,m,tol,maxitn,anorm,sigmax, &
monit,lwreq,work,lwork,ifail)
! Call repeatedly F11BSF to solve the equations
! Note that the arrays B and X are overwritten
! On final exit, X will contain the solution and B the residual
! vector
irevcm = 0
init = 'I'
ifail = 0
loop: Do
Call f11bsf(irevcm,x,b,wgt,work,lwreq,ifail)
If (irevcm/=4) Then
ifail1 = -1
If (irevcm==-1) Then
Call f11xnf('Transpose',n,nnz,a,irow,icol,'No checking',x,b, &
ifail1)
Else If (irevcm==1) Then
Call f11xnf('No transpose',n,nnz,a,irow,icol,'No checking',x,b, &
ifail1)
Else If (irevcm==2) Then
Call f11dxf('Non Hermitian','N',init,niter,n,nnz,a,irow,icol, &
'Check',x,b,diag,work(lwreq+1),ifail1)
init = 'N'
Else If (irevcm==3) Then
Call f11btf(itn,stplhs,stprhs,anorm,sigmax,work,lwreq,ifail1)
If (ifail1==0) Then
Write (nout,99999) itn
Write (nout,99998) nint(log(stplhs)/log(10.0_nag_wp))
End If
End If
If (ifail1/=0) irevcm = 6
Else
Exit loop
End If
End Do loop
! Obtain information about the computation
ifail1 = 0
Call f11btf(itn,stplhs,stprhs,anorm,sigmax,work,lwreq,ifail1)
! Print the output data
Write (nout,99997)
Write (nout,99996) 'Number of iterations for convergence: ', itn
Write (nout,99995) 'Residual norm: ', stplhs
Write (nout,99995) 'Right-hand side of termination criterion:', stprhs
Write (nout,99995) '1-norm of matrix A: ', anorm
! Output x
Write (nout,99994)
Write (nout,99993) x(1:n)
99999 Format (/1X,'Monitoring at iteration number',I4)
99998 Format (1X,' order of residual norm:',I4)
99997 Format (/1X,'Final Results')
99996 Format (1X,A,I5)
99995 Format (1X,A,1P,E11.1)
99994 Format (/2X,' Solution vector')
99993 Format (1X,'(',F8.3,',',F8.3,')')
End Program f11dxfe