* F08HPF Example Program Text * Mark 21. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER KDMAX, NMAX, MMAX PARAMETER (KDMAX=5,NMAX=20,MMAX=10) INTEGER LDAB, LDQ, LDZ PARAMETER (LDAB=KDMAX+1,LDQ=NMAX,LDZ=NMAX) CHARACTER UPLO PARAMETER (UPLO='U') DOUBLE PRECISION ZERO PARAMETER (ZERO=0.0D+0) * .. Local Scalars .. DOUBLE PRECISION ABSTOL, VL, VU INTEGER I, IFAIL, IL, INFO, IU, J, KD, M, N * .. Local Arrays .. COMPLEX *16 AB(LDAB,NMAX), Q(LDQ,NMAX), WORK(NMAX), + Z(LDZ,MMAX) DOUBLE PRECISION RWORK(7*NMAX), W(NMAX) INTEGER INDEX(NMAX), IWORK(5*NMAX) * .. External Subroutines .. EXTERNAL X04DAF, ZHBEVX * .. Intrinsic Functions .. INTRINSIC MAX, MIN * .. Executable Statements .. WRITE (NOUT,*) 'F08HPF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N, KD IF (N.LE.NMAX .AND. KD.LE.KDMAX) THEN * * Read the lower and upper bounds of the interval to be searched, * and read the upper or lower triangular part of the matrix A * from data file * READ (NIN,*) VL, VU IF (UPLO.EQ.'U') THEN READ (NIN,*) ((AB(KD+1+I-J,J),J=I,MIN(N,I+KD)),I=1,N) ELSE IF (UPLO.EQ.'L') THEN READ (NIN,*) ((AB(1+I-J,J),J=MAX(1,I-KD),I),I=1,N) END IF * * Set the absolute error tolerance for eigenvalues. With ABSTOL * set to zero, the default value is used instead * ABSTOL = ZERO * * Solve the band symmetric eigenvalue problem * CALL ZHBEVX('Vectors','Values in range',UPLO,N,KD,AB,LDAB,Q, + LDQ,VL,VU,IL,IU,ABSTOL,M,W,Z,LDZ,WORK,RWORK,IWORK, + INDEX,INFO) * IF (INFO.GE.0 .AND. M.LE.MMAX) THEN * * Print solution * WRITE (NOUT,99999) 'Number of eigenvalues found =', M WRITE (NOUT,*) WRITE (NOUT,*) 'Eigenvalues' WRITE (NOUT,99998) (W(J),J=1,M) * IFAIL = 0 CALL X04DAF('General',' ',N,M,Z,LDZ,'Selected eigenvectors', + IFAIL) IF (INFO.GT.0) THEN WRITE (NOUT,99999) + 'INFO eigenvectors failed to converge, INFO =', INFO WRITE (NOUT,*) + 'Indices of eigenvectors that did not converge' WRITE (NOUT,99997) (INDEX(J),J=1,M) END IF ELSE IF (M.GT.MMAX) THEN WRITE (NOUT,99996) 'M greater than MMAX, M =', M, + ', MMAX =', MMAX ELSE WRITE (NOUT,99999) 'Failure in ZHBEVX. INFO =', INFO END IF ELSE WRITE (NOUT,*) WRITE (NOUT,*) 'NMAX and/or KDMAX too small' END IF STOP * 99999 FORMAT (1X,A,I5) 99998 FORMAT (3X,(8F8.4)) 99997 FORMAT (3X,(8I8)) 99996 FORMAT (1X,A,I5,A,I5) END