1CHBEV(1)              LAPACK driver routine (version 3.2)             CHBEV(1)
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NAME

6       CHBEV - computes all the eigenvalues and, optionally, eigenvectors of a
7       complex Hermitian band matrix A
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SYNOPSIS

10       SUBROUTINE CHBEV( JOBZ, UPLO, N, KD, AB, LDAB, W, Z, LDZ, WORK,  RWORK,
11                         INFO )
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13           CHARACTER     JOBZ, UPLO
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15           INTEGER       INFO, KD, LDAB, LDZ, N
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17           REAL          RWORK( * ), W( * )
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19           COMPLEX       AB( LDAB, * ), WORK( * ), Z( LDZ, * )
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PURPOSE

22       CHBEV  computes  all the eigenvalues and, optionally, eigenvectors of a
23       complex Hermitian band matrix A.
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ARGUMENTS

26       JOBZ    (input) CHARACTER*1
27               = 'N':  Compute eigenvalues only;
28               = 'V':  Compute eigenvalues and eigenvectors.
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30       UPLO    (input) CHARACTER*1
31               = 'U':  Upper triangle of A is stored;
32               = 'L':  Lower triangle of A is stored.
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34       N       (input) INTEGER
35               The order of the matrix A.  N >= 0.
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37       KD      (input) INTEGER
38               The number of superdiagonals of the matrix A if UPLO = 'U',  or
39               the number of subdiagonals if UPLO = 'L'.  KD >= 0.
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41       AB      (input/output) COMPLEX array, dimension (LDAB, N)
42               On  entry,  the  upper  or lower triangle of the Hermitian band
43               matrix A, stored in the first KD+1 rows of the array.  The j-th
44               column  of  A  is  stored in the j-th column of the array AB as
45               follows: if UPLO = 'U', AB(kd+1+i-j,j) =  A(i,j)  for  max(1,j-
46               kd)<=i<=j;   if   UPLO  =  'L',  AB(1+i-j,j)     =  A(i,j)  for
47               j<=i<=min(n,j+kd).  On exit, AB is overwritten by values gener‐
48               ated  during the reduction to tridiagonal form.  If UPLO = 'U',
49               the first superdiagonal and the  diagonal  of  the  tridiagonal
50               matrix  T are returned in rows KD and KD+1 of AB, and if UPLO =
51               'L', the diagonal and first subdiagonal of T  are  returned  in
52               the first two rows of AB.
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54       LDAB    (input) INTEGER
55               The leading dimension of the array AB.  LDAB >= KD + 1.
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57       W       (output) REAL array, dimension (N)
58               If INFO = 0, the eigenvalues in ascending order.
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60       Z       (output) COMPLEX array, dimension (LDZ, N)
61               If  JOBZ  =  'V',  then if INFO = 0, Z contains the orthonormal
62               eigenvectors of the matrix A, with the i-th column of Z holding
63               the eigenvector associated with W(i).  If JOBZ = 'N', then Z is
64               not referenced.
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66       LDZ     (input) INTEGER
67               The leading dimension of the array Z.  LDZ >= 1, and if JOBZ  =
68               'V', LDZ >= max(1,N).
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70       WORK    (workspace) COMPLEX array, dimension (N)
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72       RWORK   (workspace) REAL array, dimension (max(1,3*N-2))
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74       INFO    (output) INTEGER
75               = 0:  successful exit.
76               < 0:  if INFO = -i, the i-th argument had an illegal value.
77               >  0:   if  INFO  = i, the algorithm failed to converge; i off-
78               diagonal elements of an intermediate tridiagonal form  did  not
79               converge to zero.
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83 LAPACK driver routine (version 3.N2o)vember 2008                        CHBEV(1)
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