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

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

25       JOBZ    (input) CHARACTER*1
26               = 'N':  Compute eigenvalues only;
27               = 'V':  Compute eigenvalues and eigenvectors.
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29       UPLO    (input) CHARACTER*1
30               = 'U':  Upper triangle of A is stored;
31               = 'L':  Lower triangle of A is stored.
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33       N       (input) INTEGER
34               The order of the matrix A.  N >= 0.
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36       AP      (input/output) COMPLEX array, dimension (N*(N+1)/2)
37               On  entry,  the upper or lower triangle of the Hermitian matrix
38               A, packed columnwise in a linear array.  The j-th column  of  A
39               is  stored  in  the  array AP as follows: if UPLO = 'U', AP(i +
40               (j-1)*j/2) =  A(i,j)  for  1<=i<=j;  if  UPLO  =  'L',  AP(i  +
41               (j-1)*(2*n-j)/2)  =  A(i,j)  for j<=i<=n.  On exit, AP is over‐
42               written by values generated during the reduction to tridiagonal
43               form.   If  UPLO = 'U', the diagonal and first superdiagonal of
44               the tridiagonal matrix T overwrite the  corresponding  elements
45               of  A, and if UPLO = 'L', the diagonal and first subdiagonal of
46               T overwrite the corresponding elements of A.
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48       W       (output) REAL array, dimension (N)
49               If INFO = 0, the eigenvalues in ascending order.
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51       Z       (output) COMPLEX array, dimension (LDZ, N)
52               If JOBZ = 'V', then if INFO = 0,  Z  contains  the  orthonormal
53               eigenvectors of the matrix A, with the i-th column of Z holding
54               the eigenvector associated with W(i).  If JOBZ = 'N', then Z is
55               not referenced.
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57       LDZ     (input) INTEGER
58               The  leading dimension of the array Z.  LDZ >= 1, and if JOBZ =
59               'V', LDZ >= max(1,N).
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61       WORK    (workspace) COMPLEX array, dimension (max(1, 2*N-1))
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63       RWORK   (workspace) REAL array, dimension (max(1, 3*N-2))
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65       INFO    (output) INTEGER
66               = 0:  successful exit.
67               < 0:  if INFO = -i, the i-th argument had an illegal value.
68               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
69               diagonal  elements  of an intermediate tridiagonal form did not
70               converge to zero.
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74 LAPACK driver routine (version 3.N2o)vember 2008                        CHPEV(1)
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