chpev(l) [redhat man page]

CHPEV(l)								 )								  CHPEV(l)

NAME

       CHPEV - compute all the eigenvalues and, optionally, eigenvectors of a complex Hermitian matrix in packed storage

SYNOPSIS

       SUBROUTINE CHPEV( JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, RWORK, INFO )

	   CHARACTER	 JOBZ, UPLO

	   INTEGER	 INFO, LDZ, N

	   REAL 	 RWORK( * ), W( * )

	   COMPLEX	 AP( * ), WORK( * ), Z( LDZ, * )

PURPOSE

       CHPEV computes all the eigenvalues and, optionally, eigenvectors of a complex Hermitian matrix in packed storage.

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.

       AP      (input/output) COMPLEX array, dimension (N*(N+1)/2)
	       On  entry,  the	upper  or  lower triangle of the Hermitian matrix A, packed columnwise in a linear array.  The j-th column of A is
	       stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2*n-j)/2)  =
	       A(i,j) for j<=i<=n.

	       On  exit,  AP  is  overwritten by values generated during the reduction to tridiagonal form.  If UPLO = 'U', the diagonal and first
	       superdiagonal of the tridiagonal matrix T overwrite the corresponding elements of A, and if UPLO = 'L', the diagonal and first sub-
	       diagonal of T overwrite the corresponding elements of A.

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

       Z       (output) COMPLEX array, dimension (LDZ, N)
	       If  JOBZ  =  'V',  then if INFO = 0, Z contains the orthonormal eigenvectors of the matrix A, with the i-th column of Z holding the
	       eigenvector associated with W(i).  If JOBZ = 'N', then Z is not referenced.

       LDZ     (input) INTEGER
	       The leading dimension of the array Z.  LDZ >= 1, and if JOBZ = 'V', LDZ >= max(1,N).

       WORK    (workspace) COMPLEX array, dimension (max(1, 2*N-1))

       RWORK   (workspace) REAL array, dimension (max(1, 3*N-2))

       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 							  CHPEV(l)