* F07BUF Example Program Text * Mark 15 Release. NAG Copyright 1991. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX, KLMAX, KUMAX, LDAB PARAMETER (NMAX=8,KLMAX=8,KUMAX=8,LDAB=2*KLMAX+KUMAX+1) CHARACTER NORM PARAMETER (NORM='1') * .. Local Scalars .. DOUBLE PRECISION ANORM, RCOND INTEGER I, INFO, J, K, KL, KU, N * .. Local Arrays .. COMPLEX*16 AB(LDAB,NMAX), WORK(2*NMAX) DOUBLE PRECISION RWORK(NMAX) INTEGER IPIV(NMAX) * .. External Functions .. DOUBLE PRECISION F06UBF, X02AJF EXTERNAL F06UBF, X02AJF * .. External Subroutines .. EXTERNAL ZGBCON, ZGBTRF * .. Intrinsic Functions .. INTRINSIC MAX, MIN * .. Executable Statements .. WRITE (NOUT,*) 'F07BUF Example Program Results' * Skip heading in data file READ (NIN,*) READ (NIN,*) N, KL, KU IF (N.LE.NMAX .AND. KL.LE.KLMAX .AND. KU.LE.KUMAX) THEN * * Read A 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) * * Compute norm of A * ANORM = F06UBF(NORM,N,KL,KU,AB(KL+1,1),LDAB,RWORK) * * Factorize A * CALL ZGBTRF(N,N,KL,KU,AB,LDAB,IPIV,INFO) * WRITE (NOUT,*) IF (INFO.EQ.0) THEN * * Estimate condition number * CALL ZGBCON(NORM,N,KL,KU,AB,LDAB,IPIV,ANORM,RCOND,WORK, + RWORK,INFO) * IF (RCOND.GE.X02AJF()) THEN WRITE (NOUT,99999) 'Estimate of condition number =', + 1.0D0/RCOND ELSE WRITE (NOUT,*) 'A is singular to working precision' END IF ELSE WRITE (NOUT,*) 'The factor U is singular' END IF END IF STOP * 99999 FORMAT (1X,A,1P,D10.2) END