PROGRAM f11dxfe ! F11DXF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. 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(:) ! .. 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) WRITE (nout,99999) itn, stplhs 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,99998) WRITE (nout,99997) 'Number of iterations for convergence: ', itn WRITE (nout,99996) 'Residual norm: ', stplhs WRITE (nout,99996) 'Right-hand side of termination criterion:', stprhs WRITE (nout,99996) '1-norm of matrix A: ', anorm ! Output x WRITE (nout,99995) WRITE (nout,99993) x(1:n) WRITE (nout,99994) WRITE (nout,99993) b(1:n) 99999 FORMAT (/1X,'Monitoring at iteration no.',I4/1X,1P,'residual no', & 'rm: ',E14.4) 99998 FORMAT (/1X,'Final Results') 99997 FORMAT (1X,A,I4) 99996 FORMAT (1X,A,1P,E14.4) 99995 FORMAT (/2X,' Solution vector') 99994 FORMAT (/2X,' Residual vector') 99993 FORMAT (1X,'(',1P,E16.4,',',1P,E16.4,')') END PROGRAM f11dxfe