* F08QGF Example Program Text * Mark 21 Release. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX PARAMETER (NMAX=8) INTEGER LDQ, LDT, LIWORK, LWORK PARAMETER (LDQ=NMAX,LDT=NMAX,LIWORK=(NMAX*NMAX)/4, + LWORK=(NMAX*NMAX)/2) * .. Local Scalars .. DOUBLE PRECISION S, SEP INTEGER I, IFAIL, INFO, J, M, N * .. Local Arrays .. DOUBLE PRECISION Q(LDQ,NMAX), T(LDT,NMAX), WI(NMAX), WORK(LWORK), + WR(NMAX) INTEGER IWORK(LIWORK) LOGICAL SELECT(NMAX) * .. External Subroutines .. EXTERNAL DTRSEN, X04CAF * .. Executable Statements .. WRITE (NOUT,*) 'F08QGF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N IF (N.LE.NMAX) THEN * * Read T, Q and the logical array SELECT from data file * READ (NIN,*) ((T(I,J),J=1,N),I=1,N) READ (NIN,*) ((Q(I,J),J=1,N),I=1,N) * READ (NIN,*) (SELECT(I),I=1,N) * * Reorder the Schur factor T and update the matrix Q * CALL DTRSEN('Both','Vectors',SELECT,N,T,LDT,Q,LDQ,WR,WI,M,S, + SEP,WORK,LWORK,IWORK,LIWORK,INFO) * IFAIL = 0 CALL X04CAF('General',' ',N,N,T,LDT,'Reordered Schur form', + IFAIL) * WRITE (NOUT,*) IFAIL = 0 CALL X04CAF('General',' ',N,M,Q,LDQ, + 'Basis of invariant subspace',IFAIL) * WRITE (NOUT,*) WRITE (NOUT,99999) 'Condition number estimate', + ' of the selected cluster of eigenvalues = ', 1.0D0/S WRITE (NOUT,*) WRITE (NOUT,99999) 'Condition number estimate of the spec', + 'ified invariant subspace = ', 1.0D0/SEP ELSE WRITE (NOUT,*) 'NMAX too small' END IF STOP * 99999 FORMAT (1X,A,A,1P,E10.2) END