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

DSBEV(l)					)					 DSBEV(l)

NAME
       DSBEV - compute all the eigenvalues and, optionally, eigenvectors of a real symmetric band
       matrix A

SYNOPSIS
       SUBROUTINE DSBEV( JOBZ, UPLO, N, KD, AB, LDAB, W, Z, LDZ, WORK, INFO )

	   CHARACTER	 JOBZ, UPLO

	   INTEGER	 INFO, KD, LDAB, LDZ, N

	   DOUBLE	 PRECISION AB( LDAB, * ), W( * ), WORK( * ), Z( LDZ, * )

PURPOSE
       DSBEV computes all the eigenvalues and, optionally, eigenvectors of a real symmetric  band
       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.

       KD      (input) INTEGER
	       The  number of superdiagonals of the matrix A if UPLO = 'U', or the number of sub-
	       diagonals if UPLO = 'L'.  KD >= 0.

       AB      (input/output) DOUBLE PRECISION array, dimension (LDAB, N)
	       On entry, the upper or lower triangle of the symmetric band matrix  A,  stored  in
	       the first KD+1 rows of the array.  The j-th column of A is stored in the j-th col-
	       umn of the array AB as follows:	if  UPLO  =  'U',  AB(kd+1+i-j,j)  =  A(i,j)  for
	       max(1,j-kd)<=i<=j; if UPLO = 'L', AB(1+i-j,j)	= A(i,j) for j<=i<=min(n,j+kd).

	       On exit, AB is overwritten by values generated during the reduction to tridiagonal
	       form.  If UPLO = 'U', the first superdiagonal and the diagonal of the  tridiagonal
	       matrix  T  are returned in rows KD and KD+1 of AB, and if UPLO = 'L', the diagonal
	       and first subdiagonal of T are returned in the first two rows of AB.

       LDAB    (input) INTEGER
	       The leading dimension of the array AB.  LDAB >= KD + 1.

       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.

       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 (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 				 DSBEV(l)


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