* F07CNF Example Program Text * Mark 21 Release. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX PARAMETER (NMAX=8) * .. Local Scalars .. INTEGER I, INFO, N * .. Local Arrays .. COMPLEX *16 B(NMAX), D(NMAX), DL(NMAX-1), DU(NMAX-1) * .. External Subroutines .. EXTERNAL ZGTSV * .. Executable Statements .. WRITE (NOUT,*) 'F07CNF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N IF (N.LE.NMAX) THEN * * Read the tridiagonal matrix A and the right hand side B from * data file * READ (NIN,*) (DU(I),I=1,N-1) READ (NIN,*) (D(I),I=1,N) READ (NIN,*) (DL(I),I=1,N-1) READ (NIN,*) (B(I),I=1,N) * * Solve the equations Ax = b for x * CALL ZGTSV(N,1,DL,D,DU,B,N,INFO) * IF (INFO.EQ.0) THEN * * Print solution * WRITE (NOUT,*) 'Solution' WRITE (NOUT,99999) (B(I),I=1,N) * ELSE WRITE (NOUT,99998) 'The (', INFO, ',', INFO, ')', + ' element of the factor U is zero' END IF ELSE WRITE (NOUT,*) 'NMAX too small' END IF * 99999 FORMAT (4(' (',F8.4,',',F8.4,')',:)) 99998 FORMAT (1X,A,I3,A,I3,A,A) END