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

6       CHPEV  - all the eigenvalues and, optionally, eigenvectors of a complex
7       Hermitian matrix in packed storage
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SYNOPSIS

10       SUBROUTINE CHPEV( JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, RWORK, INFO )
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12           CHARACTER     JOBZ, UPLO
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14           INTEGER       INFO, LDZ, N
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16           REAL          RWORK( * ), W( * )
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18           COMPLEX       AP( * ), WORK( * ), Z( LDZ, * )
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PURPOSE

21       CHPEV computes all the eigenvalues and, optionally, eigenvectors  of  a
22       complex Hermitian matrix in packed storage.
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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       AP      (input/output) COMPLEX array, dimension (N*(N+1)/2)
38               On  entry,  the upper or lower triangle of the Hermitian matrix
39               A, packed columnwise in a linear array.  The j-th column  of  A
40               is  stored  in  the  array AP as follows: if UPLO = 'U', AP(i +
41               (j-1)*j/2) =  A(i,j)  for  1<=i<=j;  if  UPLO  =  'L',  AP(i  +
42               (j-1)*(2*n-j)/2) = A(i,j) for j<=i<=n.
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44               On  exit,  AP  is  overwritten  by  values generated during the
45               reduction to tridiagonal form.  If UPLO = 'U', the diagonal and
46               first  superdiagonal  of the tridiagonal matrix T overwrite the
47               corresponding elements of A, and if UPLO =  'L',  the  diagonal
48               and first subdiagonal of T overwrite the corresponding elements
49               of A.
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51       W       (output) REAL array, dimension (N)
52               If INFO = 0, the eigenvalues in ascending order.
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54       Z       (output) COMPLEX array, dimension (LDZ, N)
55               If JOBZ = 'V', then if INFO = 0,  Z  contains  the  orthonormal
56               eigenvectors of the matrix A, with the i-th column of Z holding
57               the eigenvector associated with W(i).  If JOBZ = 'N', then Z is
58               not referenced.
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60       LDZ     (input) INTEGER
61               The  leading dimension of the array Z.  LDZ >= 1, and if JOBZ =
62               'V', LDZ >= max(1,N).
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64       WORK    (workspace) COMPLEX array, dimension (max(1, 2*N-1))
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66       RWORK   (workspace) REAL array, dimension (max(1, 3*N-2))
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68       INFO    (output) INTEGER
69               = 0:  successful exit.
70               < 0:  if INFO = -i, the i-th argument had an illegal value.
71               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
72               diagonal  elements  of an intermediate tridiagonal form did not
73               converge to zero.
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77 LAPACK driver routine (version 3.N1o)vember 2006                        CHPEV(1)