PROGRAM f07fgfe ! F07FGF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dlansy => f06rcf, dpocon, dpotrf, nag_wp, x02ajf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. REAL (KIND=nag_wp) :: anorm, rcond INTEGER :: i, info, lda, n CHARACTER (1) :: uplo ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: a(:,:), work(:) INTEGER, ALLOCATABLE :: iwork(:) ! .. Executable Statements .. WRITE (nout,*) 'F07FGF Example Program Results' ! Skip heading in data file READ (nin,*) READ (nin,*) n lda = n ALLOCATE (a(lda,n),work(3*n),iwork(n)) ! Read A from data file READ (nin,*) uplo IF (uplo=='U') THEN READ (nin,*) (a(i,i:n),i=1,n) ELSE IF (uplo=='L') THEN READ (nin,*) (a(i,1:i),i=1,n) END IF ! Compute norm of A ! f06rcf is the NAG name equivalent of the LAPACK auxiliary dlansy anorm = dlansy('1-norm',uplo,n,a,lda,work) ! Factorize A ! The NAG name equivalent of dpotrf is f06fdf CALL dpotrf(uplo,n,a,lda,info) WRITE (nout,*) IF (info==0) THEN ! Estimate condition number ! The NAG name equivalent of dpocon is f07fgf CALL dpocon(uplo,n,a,lda,anorm,rcond,work,iwork,info) IF (rcond>=x02ajf()) THEN WRITE (nout,99999) 'Estimate of condition number =', & 1.0_nag_wp/rcond ELSE WRITE (nout,*) 'A is singular to working precision' END IF ELSE WRITE (nout,*) 'A is not positive definite' END IF 99999 FORMAT (1X,A,1P,E10.2) END PROGRAM f07fgfe