* F04BBF Example Program Text * Mark 21 Release. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX, KLMAX, KUMAX, NRHSMX PARAMETER (NMAX=8,KLMAX=4,KUMAX=4,NRHSMX=2) INTEGER LDAB, LDB PARAMETER (LDAB=2*KLMAX+KUMAX+1,LDB=NMAX) * .. Local Scalars .. DOUBLE PRECISION ERRBND, RCOND INTEGER I, IERR, IFAIL, J, K, KL, KU, N, NRHS * .. Local Arrays .. DOUBLE PRECISION AB(LDAB,NMAX), B(LDB,NRHSMX) INTEGER IPIV(NMAX) * .. External Subroutines .. EXTERNAL F04BBF, X04CAF, X04CEF * .. Intrinsic Functions .. INTRINSIC MAX, MIN * .. Executable Statements .. WRITE (NOUT,*) 'F04BBF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N, KL, KU, NRHS IF (N.LE.NMAX .AND. KL.LE.KLMAX .AND. KU.LE.KUMAX .AND. NRHS.LE. + NRHSMX) THEN * * 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,J),J=1,NRHS),I=1,N) * * Solve the equations AX = B for X * IFAIL = 1 CALL F04BBF(N,KL,KU,NRHS,AB,LDAB,IPIV,B,LDB,RCOND,ERRBND,IFAIL) * IF (IFAIL.EQ.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) 1.0D0/RCOND WRITE (NOUT,*) WRITE (NOUT,*) + 'Estimate of error bound for computed solutions' WRITE (NOUT,99999) ERRBND ELSE IF (IFAIL.EQ.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,*) IERR = 0 CALL X04CAF('General',' ',N,NRHS,B,LDB,'Solution',IERR) * ELSE IF (IFAIL.GT.0 .AND. IFAIL.LE.N) THEN * * The upper triangular matrix U is exactly singular. Print * details of factorization * WRITE (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(I),I=1,N) ELSE WRITE (NOUT,99997) IFAIL END IF ELSE WRITE (NOUT,*) + 'One or more of NMAX, KLMAX, KUMAX or NRHSMX is too small' END IF * 99999 FORMAT (6X,1P,E9.1) 99998 FORMAT ((1X,7I11)) 99997 FORMAT (1X,' ** F04BBF returned with IFAIL = ',I5) END