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

6       CHEEV  -  computes  all  eigenvalues and, optionally, eigenvectors of a
7       complex Hermitian 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

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       A       (input/output) COMPLEX array, dimension (LDA, N)
37               On  entry,  the Hermitian matrix A.  If UPLO = 'U', the leading
38               N-by-N upper triangular part of A contains the upper triangular
39               part  of the matrix A.  If UPLO = 'L', the leading N-by-N lower
40               triangular part of A contains the lower triangular part of  the
41               matrix A.  On exit, if JOBZ = 'V', then if INFO = 0, A contains
42               the orthonormal eigenvectors of the matrix A.  If JOBZ  =  'N',
43               then on exit the lower triangle (if UPLO='L') or the upper tri‐
44               angle (if UPLO='U') of A, including the diagonal, is destroyed.
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46       LDA     (input) INTEGER
47               The leading dimension of the array A.  LDA >= max(1,N).
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49       W       (output) REAL array, dimension (N)
50               If INFO = 0, the eigenvalues in ascending order.
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52       WORK    (workspace/output) COMPLEX array, dimension (MAX(1,LWORK))
53               On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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55       LWORK   (input) INTEGER
56               The length of the array  WORK.   LWORK  >=  max(1,2*N-1).   For
57               optimal  efficiency,  LWORK >= (NB+1)*N, where NB is the block‐
58               size for CHETRD returned by ILAENV.  If  LWORK  =  -1,  then  a
59               workspace  query  is  assumed;  the routine only calculates the
60               optimal size of the WORK array, returns this value as the first
61               entry  of the WORK array, and no error message related to LWORK
62               is issued by XERBLA.
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64       RWORK   (workspace) REAL array, dimension (max(1, 3*N-2))
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66       INFO    (output) INTEGER
67               = 0:  successful exit
68               < 0:  if INFO = -i, the i-th argument had an illegal value
69               > 0:  if INFO = i, the algorithm failed  to  converge;  i  off-
70               diagonal  elements  of an intermediate tridiagonal form did not
71               converge to zero.
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75 LAPACK driver routine (version 3.N2o)vember 2008                        CHEEV(1)
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