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RedHat 9 (Linux i386) - man page for dsyev (redhat section l)

DSYEV(l)					)					 DSYEV(l)

NAME
       DSYEV - compute all eigenvalues and, optionally, eigenvectors of a real symmetric matrix A

SYNOPSIS
       SUBROUTINE DSYEV( JOBZ, UPLO, N, A, LDA, W, WORK, LWORK, INFO )

	   CHARACTER	 JOBZ, UPLO

	   INTEGER	 INFO, LDA, LWORK, N

	   DOUBLE	 PRECISION A( LDA, * ), W( * ), WORK( * )

PURPOSE
       DSYEV computes all eigenvalues and, optionally, eigenvectors of a real symmetric matrix A.

ARGUMENTS
       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) DOUBLE PRECISION array, dimension (LDA, N)
	       On  entry, the symmetric matrix A.  If UPLO = 'U', the leading N-by-N upper trian-
	       gular part of A contains the upper triangular part of the matrix  A.   If  UPLO	=
	       'L',  the  leading N-by-N lower triangular part of A contains the lower triangular
	       part of the matrix A.  On exit, if JOBZ = 'V', then if INFO = 0,  A  contains  the
	       orthonormal  eigenvectors  of the matrix A.  If JOBZ = 'N', then on exit the lower
	       triangle (if UPLO='L') or the upper triangle (if UPLO='U')  of  A,  including  the
	       diagonal, is destroyed.

       LDA     (input) INTEGER
	       The leading dimension of the array A.  LDA >= max(1,N).

       W       (output) DOUBLE PRECISION array, dimension (N)
	       If INFO = 0, the eigenvalues in ascending order.

       WORK    (workspace/output) DOUBLE PRECISION array, dimension (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).  For optimal efficiency,
	       LWORK >= (NB+2)*N, where NB is the blocksize for DSYTRD returned by ILAENV.

	       If LWORK = -1, then a workspace query is assumed; the routine only calculates  the
	       optimal	size of the WORK array, returns this value as the first entry of the WORK
	       array, and no error 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 off-diagonal elements of an
	       intermediate tridiagonal form did not converge to zero.

LAPACK version 3.0			   15 June 2000 				 DSYEV(l)


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