DSPEV man page on IRIX

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DSPEV(3F)							     DSPEV(3F)

NAME
     DSPEV - compute all the eigenvalues and, optionally, eigenvectors of a
     real symmetric matrix A in packed storage

SYNOPSIS
     SUBROUTINE DSPEV( JOBZ, UPLO, N, AP, W, Z, LDZ, WORK, INFO )

	 CHARACTER     JOBZ, UPLO

	 INTEGER       INFO, LDZ, N

	 DOUBLE	       PRECISION AP( * ), W( * ), WORK( * ), Z( LDZ, * )

PURPOSE
     DSPEV computes all the eigenvalues and, optionally, eigenvectors of a
     real symmetric matrix A 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) DOUBLE PRECISION array, dimension (N*(N+1)/2)
	     On entry, the upper or lower triangle of the symmetric 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 subdiagonal of T overwrite the corresponding elements of A.

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

     Z	     (output) DOUBLE PRECISION 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.

									Page 1

DSPEV(3F)							     DSPEV(3F)

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

     WORK    (workspace) DOUBLE PRECISION array, dimension (3*N)

     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.

									Page 2

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