PROGRAM f04bbfe ! F04BBF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : f04bbf, nag_wp, x04caf, x04cef ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. REAL (KIND=nag_wp) :: errbnd, rcond INTEGER :: i, ierr, ifail, j, k, kl, ku, ldab, & ldb, n, nrhs ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: ab(:,:), b(:,:) INTEGER, ALLOCATABLE :: ipiv(:) ! .. Intrinsic Functions .. INTRINSIC max, min ! .. Executable Statements .. WRITE (nout,*) 'F04BBF Example Program Results' WRITE (nout,*) FLUSH (nout) ! Skip heading in data file READ (nin,*) READ (nin,*) n, kl, ku, nrhs ldab = 2*kl + ku + 1 ldb = n ALLOCATE (ab(ldab,n),b(ldb,nrhs),ipiv(n)) ! Read A and B from data file k = kl + ku + 1 READ (nin,*) ((ab(k+i-j,j),j=max(i-kl,1),min(i+ku,n)),i=1,n) READ (nin,*) (b(i,1:nrhs),i=1,n) ! Solve the equations AX = B for X ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 1 CALL f04bbf(n,kl,ku,nrhs,ab,ldab,ipiv,b,ldb,rcond,errbnd,ifail) IF (ifail==0) THEN ! Print solution, estimate of condition number and approximate ! error bound ierr = 0 CALL x04caf('General',' ',n,nrhs,b,ldb,'Solution',ierr) WRITE (nout,*) WRITE (nout,*) 'Estimate of condition number' WRITE (nout,99999) 1.0E0_nag_wp/rcond WRITE (nout,*) WRITE (nout,*) 'Estimate of error bound for computed solutions' WRITE (nout,99999) errbnd ELSE IF (ifail==n+1) THEN ! Matrix A is numerically singular. Print estimate of ! reciprocal of condition number and solution WRITE (nout,*) WRITE (nout,*) 'Estimate of reciprocal of condition number' WRITE (nout,99999) rcond WRITE (nout,*) FLUSH (nout) ierr = 0 CALL x04caf('General',' ',n,nrhs,b,ldb,'Solution',ierr) ELSE IF (ifail>0 .AND. ifail<=n) THEN ! The upper triangular matrix U is exactly singular. Print ! details of factorization WRITE (nout,*) FLUSH (nout) ierr = 0 CALL x04cef(n,n,kl,kl+ku,ab,ldab,'Details of factorization',ierr) ! Print pivot indices WRITE (nout,*) WRITE (nout,*) 'Pivot indices' WRITE (nout,99998) ipiv(1:n) ELSE WRITE (nout,99997) ifail END IF 99999 FORMAT (6X,1P,E9.1) 99998 FORMAT ((1X,7I11)) 99997 FORMAT (1X,' ** F04BBF returned with IFAIL = ',I5) END PROGRAM f04bbfe