PROGRAM f07crfe ! F07CRF Example Program Text ! Mark 23 Release. NAG Copyright 2011. ! .. Use Statements .. USE nag_library, ONLY : nag_wp, zgttrf ! .. Implicit None Statement .. IMPLICIT NONE ! .. Parameters .. INTEGER, PARAMETER :: nin = 5, nout = 6 ! .. Local Scalars .. INTEGER :: info, n ! .. Local Arrays .. COMPLEX (KIND=nag_wp), ALLOCATABLE :: d(:), dl(:), du(:), du2(:) INTEGER, ALLOCATABLE :: ipiv(:) ! .. Executable Statements .. WRITE (nout,*) 'F07CRF Example Program Results' WRITE (nout,*) ! Skip heading in data file READ (nin,*) READ (nin,*) n ALLOCATE (d(n),dl(n-1),du(n-1),du2(n-2),ipiv(n)) ! Read the tridiagonal matrix A from data file READ (nin,*) du(1:n-1) READ (nin,*) d(1:n) READ (nin,*) dl(1:n-1) ! Factorize the tridiagonal matrix A ! The NAG name equivalent of zgttrf is f07crf CALL zgttrf(n,dl,d,du,du2,ipiv,info) IF (info>0) THEN WRITE (nout,99999) 'The (', info, ',', info, ')', & ' element of the factor U is zero' END IF ! Print details of the factorization WRITE (nout,*) 'Details of factorization' WRITE (nout,*) WRITE (nout,*) ' Second super-diagonal of U' WRITE (nout,99998) du2(1:n-2) WRITE (nout,*) WRITE (nout,*) ' First super-diagonal of U' WRITE (nout,99998) du(1:n-1) WRITE (nout,*) WRITE (nout,*) ' Main diagonal of U' WRITE (nout,99998) d(1:n) WRITE (nout,*) WRITE (nout,*) ' Multipliers' WRITE (nout,99998) dl(1:n-1) WRITE (nout,*) WRITE (nout,*) ' Vector of interchanges' WRITE (nout,99997) ipiv(1:n) 99999 FORMAT (1X,A,I3,A,I3,A,A) 99998 FORMAT (4(' (',F8.4,',',F8.4,')':)) 99997 FORMAT (1X,5I7) END PROGRAM f07crfe