PROGRAM f08nbfe ! F08NBF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : dgeevx, nag_wp, x02ajf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nb = 64, nin = 5, nout = 6 ! .. Local Scalars .. COMPLEX (KIND=nag_wp) :: eig REAL (KIND=nag_wp) :: abnrm, eps, erbnd, rcnd, tol INTEGER :: i, ihi, ilo, info, j, lda, ldvl, & ldvr, lwork, n ! .. Local Arrays .. REAL (KIND=nag_wp), ALLOCATABLE :: a(:,:), rconde(:), rcondv(:), & scale(:), vl(:,:), vr(:,:), wi(:), & work(:), wr(:) REAL (KIND=nag_wp) :: dummy(1) INTEGER, ALLOCATABLE :: iwork(:) ! .. Intrinsic Functions .. INTRINSIC cmplx, max, nint ! .. Executable Statements .. WRITE (nout,*) 'F08NBF Example Program Results' ! Skip heading in data file READ (nin,*) READ (nin,*) n lda = n ldvl = n ldvr = n lwork = (2+nb)*n ALLOCATE (a(lda,n),rconde(n),rcondv(n),scale(n),vl(ldvl,n),vr(ldvr,n), & wi(n),wr(n),iwork(2*n-2)) ! Use routine workspace query to get optimal workspace. lwork = -1 ! The NAG name equivalent of dgeevx is f08nbf CALL dgeevx('Balance','Vectors (left)','Vectors (right)', & 'Both reciprocal condition numbers',n,a,lda,wr,wi,vl,ldvl,vr,ldvr, & ilo,ihi,scale,abnrm,rconde,rcondv,dummy,lwork,iwork,info) ! Make sure that there is enough workspace for blocksize nb. lwork = max((nb+2)*n,nint(dummy(1))) ALLOCATE (work(lwork)) ! Read the matrix A from data file READ (nin,*) (a(i,1:n),i=1,n) ! Solve the eigenvalue problem ! The NAG name equivalent of dgeevx is f08nbf CALL dgeevx('Balance','Vectors (left)','Vectors (right)', & 'Both reciprocal condition numbers',n,a,lda,wr,wi,vl,ldvl,vr,ldvr, & ilo,ihi,scale,abnrm,rconde,rcondv,work,lwork,iwork,info) IF (info==0) THEN ! Compute the machine precision eps = x02ajf() tol = eps*abnrm ! Print the eigenvalues and vectors, and associated condition ! number and bounds DO j = 1, n ! Print information on jth eigenvalue WRITE (nout,*) IF (wi(j)==0.0E0_nag_wp) THEN WRITE (nout,99999) 'Eigenvalue(', j, ') = ', wr(j) ELSE eig = cmplx(wr(j),wi(j),kind=nag_wp) WRITE (nout,99998) 'Eigenvalue(', j, ') = ', eig END IF rcnd = rconde(j) WRITE (nout,*) WRITE (nout,99997) 'Reciprocal condition number = ', rcnd IF (rcnd>0.0E0_nag_wp) THEN erbnd = tol/rcnd WRITE (nout,99997) 'Error bound = ', erbnd ELSE WRITE (nout,*) 'Error bound is infinite' END IF ! Print information on jth eigenvector WRITE (nout,*) WRITE (nout,99996) 'Eigenvector(', j, ')' IF (wi(j)==0.0E0_nag_wp) THEN WRITE (nout,99995) vr(1:n,j) ELSE IF (wi(j)>0.0E0_nag_wp) THEN WRITE (nout,99994) (vr(i,j),vr(i,j+1),i=1,n) ELSE WRITE (nout,99994) (vr(i,j-1),-vr(i,j),i=1,n) END IF rcnd = rcondv(j) WRITE (nout,*) WRITE (nout,99997) 'Reciprocal condition number = ', rcnd IF (rcnd>0.0E0_nag_wp) THEN erbnd = tol/rcnd WRITE (nout,99997) 'Error bound = ', erbnd ELSE WRITE (nout,*) 'Error bound is infinite' END IF END DO ELSE WRITE (nout,*) WRITE (nout,99993) 'Failure in DGEEVX. INFO = ', info END IF 99999 FORMAT (1X,A,I2,A,1P,E11.4) 99998 FORMAT (1X,A,I2,A,'(',1P,E11.4,',',1P,E11.4,')') 99997 FORMAT (1X,A,1P,E8.1) 99996 FORMAT (1X,A,I2,A) 99995 FORMAT (1X,1P,E11.4) 99994 FORMAT (1X,'(',1P,E11.4,',',1P,E11.4,')') 99993 FORMAT (1X,A,I4) END PROGRAM f08nbfe