1CHBEV(1)              LAPACK driver routine (version 3.1)             CHBEV(1)
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NAME

6       CHBEV  - all the eigenvalues and, optionally, eigenvectors of a complex
7       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

27       JOBZ    (input) CHARACTER*1
28               = 'N':  Compute eigenvalues only;
29               = 'V':  Compute eigenvalues and eigenvectors.
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31       UPLO    (input) CHARACTER*1
32               = 'U':  Upper triangle of A is stored;
33               = 'L':  Lower triangle of A is stored.
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35       N       (input) INTEGER
36               The order of the matrix A.  N >= 0.
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38       KD      (input) INTEGER
39               The number of superdiagonals of the matrix A if UPLO = 'U',  or
40               the number of subdiagonals if UPLO = 'L'.  KD >= 0.
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42       AB      (input/output) COMPLEX array, dimension (LDAB, N)
43               On  entry,  the  upper  or lower triangle of the Hermitian band
44               matrix A, stored in the first KD+1 rows of the array.  The j-th
45               column  of  A  is  stored in the j-th column of the array AB as
46               follows: if UPLO = 'U', AB(kd+1+i-j,j) =  A(i,j)  for  max(1,j-
47               kd)<=i<=j;   if   UPLO  =  'L',  AB(1+i-j,j)     =  A(i,j)  for
48               j<=i<=min(n,j+kd).
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50               On exit, AB is  overwritten  by  values  generated  during  the
51               reduction to tridiagonal form.  If UPLO = 'U', the first super‐
52               diagonal and the diagonal  of  the  tridiagonal  matrix  T  are
53               returned  in  rows  KD  and  KD+1 of AB, and if UPLO = 'L', the
54               diagonal and first subdiagonal of T are returned in  the  first
55               two rows of AB.
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57       LDAB    (input) INTEGER
58               The leading dimension of the array AB.  LDAB >= KD + 1.
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60       W       (output) REAL array, dimension (N)
61               If INFO = 0, the eigenvalues in ascending order.
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63       Z       (output) COMPLEX array, dimension (LDZ, N)
64               If  JOBZ  =  'V',  then if INFO = 0, Z contains the orthonormal
65               eigenvectors of the matrix A, with the i-th column of Z holding
66               the eigenvector associated with W(i).  If JOBZ = 'N', then Z is
67               not referenced.
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69       LDZ     (input) INTEGER
70               The leading dimension of the array Z.  LDZ >= 1, and if JOBZ  =
71               'V', LDZ >= max(1,N).
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73       WORK    (workspace) COMPLEX array, dimension (N)
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75       RWORK   (workspace) REAL array, dimension (max(1,3*N-2))
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77       INFO    (output) INTEGER
78               = 0:  successful exit.
79               < 0:  if INFO = -i, the i-th argument had an illegal value.
80               >  0:   if  INFO  = i, the algorithm failed to converge; i off-
81               diagonal elements of an intermediate tridiagonal form  did  not
82               converge to zero.
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86 LAPACK driver routine (version 3.N1o)vember 2006                        CHBEV(1)