PROGRAM f11drfe ! F11DRF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : f11brf, f11bsf, f11btf, f11drf, f11xnf, 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, ifail1, irevcm, iterm, & itn, liwork, lwneed, lwork, m, & maxitn, monit, n, nnz CHARACTER (1) :: ckdrf, ckxnf, norm, precon, trans, & weight CHARACTER (8) :: method ! .. Local Arrays .. COMPLEX (KIND=nag_wp), ALLOCATABLE :: a(:), b(:), rdiag(:), work(:), x(:) REAL (KIND=nag_wp), ALLOCATABLE :: wgt(:) INTEGER, ALLOCATABLE :: icol(:), irow(:), iwork(:) ! .. Intrinsic Functions .. INTRINSIC max ! .. Executable Statements .. WRITE (nout,*) 'F11DRF Example Program Results' WRITE (nout,*) ! Skip heading in data file READ (nin,*) ! Read algorithmic parameters READ (nin,*) n, m READ (nin,*) nnz lwork = max(121+n*(3+m)+m*(m+5),120+7*n,120+(2*n+m)*(m+2)+2*n,120+10*n) liwork = 2*n + 1 ALLOCATE (a(nnz),b(n),rdiag(n),work(lwork),x(n),wgt(n),icol(nnz), & irow(nnz),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 rhs vector b and initial approximate solution x READ (nin,*) b(1:n) READ (nin,*) x(1:n) ! Call F11BRF 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 f11brf(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)/=(0.0E0_nag_wp,0.0E0_nag_wp)) THEN rdiag(irow(i)) = (1.0E0_nag_wp,0.0E0_nag_wp)/a(i) ELSE WRITE (nout,*) 'Matrix has a zero diagonal element' GO TO 20 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 20 END IF IF (iwork(i)>=2) THEN WRITE (nout,*) 'Matrix has a multiple diagonal element' GO TO 20 END IF END DO END IF ! Call F11BSF to solve the linear system irevcm = 0 ckxnf = 'C' ckdrf = 'C' ifail = 1 LOOP: DO CALL f11bsf(irevcm,x,b,wgt,work,lwork,ifail) IF (irevcm/=4) THEN ifail1 = 1 SELECT CASE (irevcm) CASE (1) ! Compute matrix-vector product trans = 'N' CALL f11xnf(trans,n,nnz,a,irow,icol,ckxnf,x,b,ifail1) ckxnf = 'N' CASE (-1) ! Compute conjugate transposed matrix-vector product trans = 'T' CALL f11xnf(trans,n,nnz,a,irow,icol,ckxnf,x,b,ifail1) ckxnf = 'N' CASE (2) ! SSOR preconditioning trans = 'N' CALL f11drf(trans,n,nnz,a,irow,icol,rdiag,omega,ckdrf,x,b, & iwork,ifail1) ckdrf = 'N' END SELECT IF (ifail1/=0) irevcm = 6 ELSE IF (ifail==0) THEN ! Termination ifail = 0 CALL f11btf(itn,stplhs,stprhs,anorm,sigmax,work,lwork,ifail) WRITE (nout,99996) itn WRITE (nout,99997) 'Matrix norm =', anorm WRITE (nout,99997) 'Final residual norm =', stplhs WRITE (nout,*) ! Output x WRITE (nout,*) ' X' WRITE (nout,99998) x(1:n) EXIT LOOP ELSE WRITE (nout,99999) ifail EXIT LOOP END IF END DO LOOP 20 CONTINUE 99999 FORMAT (1X/1X,' ** F11BSF returned with IFAIL = ',I5) 99998 FORMAT (1X,'(',1P,E16.4,',',1P,E16.4,')') 99997 FORMAT (1X,A,1P,E16.3) 99996 FORMAT (1X,'Converged in',I10,' iterations') END PROGRAM f11drfe