* F07PGF Example Program Text * Mark 15 Release. NAG Copyright 1991. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX PARAMETER (NMAX=8) * .. Local Scalars .. DOUBLE PRECISION ANORM, RCOND INTEGER I, INFO, J, N CHARACTER UPLO * .. Local Arrays .. DOUBLE PRECISION AP(NMAX*(NMAX+1)/2), WORK(2*NMAX) INTEGER IPIV(NMAX), IWORK(NMAX) * .. External Functions .. DOUBLE PRECISION F06RDF, X02AJF EXTERNAL F06RDF, X02AJF * .. External Subroutines .. EXTERNAL DSPCON, DSPTRF * .. Executable Statements .. WRITE (NOUT,*) 'F07PGF Example Program Results' * Skip heading in data file READ (NIN,*) READ (NIN,*) N IF (N.LE.NMAX) THEN * * Read A from data file * READ (NIN,*) UPLO IF (UPLO.EQ.'U') THEN READ (NIN,*) ((AP(I+J*(J-1)/2),J=I,N),I=1,N) ELSE IF (UPLO.EQ.'L') THEN READ (NIN,*) ((AP(I+(2*N-J)*(J-1)/2),J=1,I),I=1,N) END IF * * Compute norm of A * ANORM = F06RDF('1-norm',UPLO,N,AP,WORK) * * Factorize A * CALL DSPTRF(UPLO,N,AP,IPIV,INFO) * WRITE (NOUT,*) IF (INFO.EQ.0) THEN * * Estimate condition number * CALL DSPCON(UPLO,N,AP,IPIV,ANORM,RCOND,WORK,IWORK,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 D is singular' END IF END IF STOP * 99999 FORMAT (1X,A,1P,E10.2) END