*     F11DBF Example Program Text
*     Mark 18 Release. NAG Copyright 1997.
*     .. Parameters ..
      INTEGER          NIN, NOUT
      PARAMETER        (NIN=5,NOUT=6)
      INTEGER          NMAX, LA, LIWORK
      PARAMETER        (NMAX=1000,LA=10000,LIWORK=7*NMAX+2)
*     .. Local Scalars ..
      DOUBLE PRECISION DTOL
      INTEGER          I, IFAIL, LFILL, N, NNZ, NNZC, NPIVM
      CHARACTER        CHECK, MILU, PSTRAT, TRANS
*     .. Local Arrays ..
      DOUBLE PRECISION A(LA), X(NMAX), Y(NMAX)
      INTEGER          ICOL(LA), IDIAG(NMAX), IPIVP(NMAX), IPIVQ(NMAX),
     +                 IROW(LA), ISTR(NMAX+1), IWORK(LIWORK)
*     .. External Subroutines ..
      EXTERNAL         F11DAF, F11DBF
*     .. Executable Statements ..
      WRITE (NOUT,*) 'F11DBF Example Program Results'
      WRITE (NOUT,*)
*
*     Skip heading in data file
*
      READ (NIN,*)
*
*     Read order of matrix and number of non-zero entries
*
      READ (NIN,*) N
      IF (N.LE.NMAX) THEN
         READ (NIN,*) NNZ
*
*        Read the matrix A
*
         DO 20 I = 1, NNZ
            READ (NIN,*) A(I), IROW(I), ICOL(I)
   20    CONTINUE
*
*        Read the vector y
*
         READ (NIN,*) (Y(I),I=1,N)
*
*        Calculate LU factorization
*
         LFILL = -1
         DTOL = 0.D0
         PSTRAT = 'C'
         MILU = 'N'
         IFAIL = 1
*
         CALL F11DAF(N,NNZ,A,LA,IROW,ICOL,LFILL,DTOL,PSTRAT,MILU,IPIVP,
     +               IPIVQ,ISTR,IDIAG,NNZC,NPIVM,IWORK,LIWORK,IFAIL)
         IF (IFAIL.EQ.0) THEN
*
*           Check value of NPIVM
*
            IF (NPIVM.GT.0) THEN
*
               WRITE (NOUT,*) 'Factorization is not complete'
*
            ELSE
*
*              Solve P L D U x = y
*
               TRANS = 'N'
               CHECK = 'C'
*
               IFAIL = 1
               CALL F11DBF(TRANS,N,A,LA,IROW,ICOL,IPIVP,IPIVQ,ISTR,
     +                     IDIAG,CHECK,Y,X,IFAIL)
               IF (IFAIL.EQ.0) THEN
*
*                 Output results
*
                  WRITE (NOUT,*) ' Solution of linear system'
                  DO 40 I = 1, N
                     WRITE (NOUT,'(E16.4)') X(I)
   40             CONTINUE
*
               ELSE
                  WRITE (NOUT,99999) IFAIL
               END IF
            END IF
*
         ELSE
            WRITE (NOUT,99998) IFAIL
         END IF
      END IF
*
99999 FORMAT (1X,/1X,' ** F11DBF returned with IFAIL = ',I5)
99998 FORMAT (1X,/1X,' ** F11DAF returned with IFAIL = ',I5)
      END