* F04BGF Example Program Text * Mark 21 Release. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX, NRHSMX PARAMETER (NMAX=8,NRHSMX=2) INTEGER LDB PARAMETER (LDB=NMAX) * .. Local Scalars .. DOUBLE PRECISION ERRBND, RCOND INTEGER I, IERR, IFAIL, J, N, NRHS * .. Local Arrays .. DOUBLE PRECISION B(LDB,NRHSMX), D(NMAX), E(NMAX-1) * .. External Subroutines .. EXTERNAL F04BGF, X04CAF * .. Executable Statements .. WRITE (NOUT,*) 'F04BGF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N, NRHS IF (N.LE.NMAX .AND. NRHS.LE.NRHSMX) THEN * * Read A from data file * READ (NIN,*) (D(I),I=1,N) READ (NIN,*) (E(I),I=1,N-1) * * Read B from data file * READ (NIN,*) ((B(I,J),J=1,NRHS),I=1,N) * * Solve the equations AX = B for X * IFAIL = 1 CALL F04BGF(N,NRHS,D,E,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 WRITE (NOUT,99998) 'The leading minor of order ', IFAIL, + ' is not positive definite' ELSE WRITE (NOUT,99997) IFAIL END IF ELSE WRITE (NOUT,*) 'NMAX and/or NRHSMX too small' END IF * 99999 FORMAT (6X,1P,E9.1) 99998 FORMAT (1X,A,I3,A) 99997 FORMAT (1X,' ** F04BGF returned with IFAIL = ',I5) END