I want to use a routine from lapack
SSYEV( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO )
CHARACTER JOBZ, UPLO
INTEGER INFO, LDA, LWORK, N
REAL A( LDA, * ), W( * ), WORK( * )
SSYEV computes all eigenvalues and, optionally, eigenvectors of a
symmetric matrix A.
JOBZ (input) CHARACTER*1
= 'N': Compute eigenvalues only;
= 'V': Compute eigenvalues and eigenvectors.
UPLO (input) CHARACTER*1
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input/output) REAL array, dimension (LDA, N)
On entry, the symmetric matrix A. If UPLO = 'U', the
leading N-by-N upper triangular part of A contains the
part of the matrix A. If UPLO = 'L', the leading N-by-N
triangular part of A contains the lower triangular part of
matrix A. On exit, if JOBZ = 'V', then if INFO = 0, A
the orthonormal eigenvectors of the matrix A. If JOBZ =
then on exit the lower triangle (if UPLO='L') or the upper
angle (if UPLO='U') of A, including the diagonal, is
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
W (output) REAL array, dimension (N)
If INFO = 0, the eigenvalues in ascending order.
WORK (workspace/output) REAL array, dimension (MAX(1,LWORK))
On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
LWORK (input) INTEGER
The length of the array WORK. LWORK >= max(1,3*N-1).
optimal efficiency, LWORK >= (NB+2)*N, where NB is the
size for SSYTRD returned by ILAENV.
If LWORK = -1, then a workspace query is assumed; the
only calculates the optimal size of the WORK array,
this value as the first entry of the WORK array, and no
message related to LWORK is issued by XERBLA.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the algorithm failed to converge; i
diagonal elements of an intermediate tridiagonal form did
converge to zero.
LAPACK driver routine (version 3November 2006
*here I do not understand LDA, WORK and LWORK. how to know what will be
LWORK and LDA.
with best regards
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