Program f11ddfe ! F11DDF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: f11bdf, f11bef, f11bff, f11ddf, f11xaf, nag_wp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=nag_wp) :: anorm, omega, sigmax, stplhs, & stprhs, tol Integer :: i, ifail, irevcm, iterm, itn, la, & liwork, lwneed, lwork, m, maxitn, & monit, n, nnz Character (1) :: ckddf, ckxaf, norm, precon, trans, & weight Character (8) :: method ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: a(:), b(:), rdiag(:), wgt(:), & work(:), x(:) Integer, Allocatable :: icol(:), irow(:), iwork(:) ! .. Intrinsic Procedures .. Intrinsic :: max ! .. Executable Statements .. Write (nout,*) 'F11DDF Example Program Results' Write (nout,*) ! Skip heading in data file Read (nin,*) ! Read algorithmic parameters Read (nin,*) n, m Read (nin,*) nnz la = 3*nnz lwork = max(n*(m+3)+m*(m+5)+101,7*n+100,(2*n+m)*(m+2)+n+100,10*n+100) liwork = 2*n + 1 Allocate (a(la),b(n),rdiag(n),wgt(n),work(lwork),x(n),icol(la),irow(la), & iwork(liwork)) Read (nin,*) method Read (nin,*) precon, norm, iterm Read (nin,*) tol, maxitn Read (nin,*) anorm, sigmax Read (nin,*) omega ! Read 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 x Read (nin,*) b(1:n) Read (nin,*) x(1:n) ! Call F11BDF to initialize solver weight = 'N' monit = 0 ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call f11bdf(method,precon,norm,weight,iterm,n,m,tol,maxitn,anorm,sigmax, & monit,lwneed,work,lwork,ifail) ! Calculate reciprocal diagonal matrix elements if necessary If (precon=='P' .Or. precon=='p') Then iwork(1:n) = 0 Do i = 1, nnz If (irow(i)==icol(i)) Then iwork(irow(i)) = iwork(irow(i)) + 1 If (a(i)/=0.E0_nag_wp) Then rdiag(irow(i)) = 1.E0_nag_wp/a(i) Else Write (nout,*) 'Matrix has a zero diagonal element' Go To 100 End If End If End Do Do i = 1, n If (iwork(i)==0) Then Write (nout,*) 'Matrix has a missing diagonal element' Go To 100 End If If (iwork(i)>=2) Then Write (nout,*) 'Matrix has a multiple diagonal element' Go To 100 End If End Do End If ! Call F11BEF to solve the linear system irevcm = 0 ckxaf = 'C' ckddf = 'C' loop: Do ifail = 0 Call f11bef(irevcm,x,b,wgt,work,lwork,ifail) Select Case (irevcm) Case (1) ! Compute matrix-vector product trans = 'N' Call f11xaf(trans,n,nnz,a,irow,icol,ckxaf,x,b,ifail) ckxaf = 'N' Case (-1) ! Compute transposed matrix-vector product trans = 'T' Call f11xaf(trans,n,nnz,a,irow,icol,ckxaf,x,b,ifail) ckxaf = 'N' Case (2) ! SSOR preconditioning trans = 'N' Call f11ddf(trans,n,nnz,a,irow,icol,rdiag,omega,ckddf,x,b,iwork, & ifail) ckddf = 'N' Case (4) ! Termination ifail = 0 Call f11bff(itn,stplhs,stprhs,anorm,sigmax,work,lwork,ifail) Write (nout,'(A,I10,A)') ' Converged in', itn, ' iterations' Write (nout,'(A,1P,E16.3)') ' Matrix norm =', anorm Write (nout,'(A,1P,E16.3)') ' Final residual norm =', stplhs Write (nout,*) ! Output x Write (nout,*) ' X' Write (nout,'(1X,1P,E16.4)') x(1:n) Exit loop Case Default Exit loop End Select End Do loop 100 Continue End Program f11ddfe