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

6       CHEEV - all eigenvalues and, optionally, eigenvectors of a complex Her‐
7       mitian matrix A
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SYNOPSIS

10       SUBROUTINE CHEEV( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, RWORK, INFO )
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12           CHARACTER     JOBZ, UPLO
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14           INTEGER       INFO, LDA, LWORK, N
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16           REAL          RWORK( * ), W( * )
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18           COMPLEX       A( LDA, * ), WORK( * )
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PURPOSE

21       CHEEV computes all eigenvalues and, optionally, eigenvectors of a  com‐
22       plex Hermitian 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       A       (input/output) COMPLEX array, dimension (LDA, N)
38               On  entry,  the Hermitian matrix A.  If UPLO = 'U', the leading
39               N-by-N upper triangular part of A contains the upper triangular
40               part  of the matrix A.  If UPLO = 'L', the leading N-by-N lower
41               triangular part of A contains the lower triangular part of  the
42               matrix A.  On exit, if JOBZ = 'V', then if INFO = 0, A contains
43               the orthonormal eigenvectors of the matrix A.  If JOBZ  =  'N',
44               then on exit the lower triangle (if UPLO='L') or the upper tri‐
45               angle (if UPLO='U') of A, including the diagonal, is destroyed.
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47       LDA     (input) INTEGER
48               The leading dimension of the array A.  LDA >= max(1,N).
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50       W       (output) REAL array, dimension (N)
51               If INFO = 0, the eigenvalues in ascending order.
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53       WORK    (workspace/output) COMPLEX array, dimension (MAX(1,LWORK))
54               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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56       LWORK   (input) INTEGER
57               The length of the array  WORK.   LWORK  >=  max(1,2*N-1).   For
58               optimal  efficiency,  LWORK >= (NB+1)*N, where NB is the block‐
59               size for CHETRD returned by ILAENV.
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61               If LWORK = -1, then a workspace query is assumed;  the  routine
62               only  calculates  the  optimal  size of the WORK array, returns
63               this value as the first entry of the WORK array, and  no  error
64               message related to LWORK is issued by XERBLA.
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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                        CHEEV(1)