zlaed0.f man page

zlaed0.f —

Synopsis

Functions/Subroutines

subroutine zlaed0 (QSIZ, N, D, E, Q, LDQ, QSTORE, LDQS, RWORK, IWORK, INFO)
ZLAED0 used by sstedc. Computes all eigenvalues and corresponding eigenvectors of an unreduced symmetric tridiagonal matrix using the divide and conquer method.

Function/Subroutine Documentation

subroutine zlaed0 (integer QSIZ, integer N, double precision, dimension( * ) D, double precision, dimension( * ) E, complex*16, dimension( ldq, * ) Q, integer LDQ, complex*16, dimension( ldqs, * ) QSTORE, integer LDQS, double precision, dimension( * ) RWORK, integer, dimension( * ) IWORK, integer INFO)

ZLAED0 used by sstedc. Computes all eigenvalues and corresponding eigenvectors of an unreduced symmetric tridiagonal matrix using the divide and conquer method.  

Purpose:

 Using the divide and conquer method, ZLAED0 computes all eigenvalues
 of a symmetric tridiagonal matrix which is one diagonal block of
 those from reducing a dense or band Hermitian matrix and
 corresponding eigenvectors of the dense or band matrix.
Parameters:

QSIZ

          QSIZ is INTEGER
         The dimension of the unitary matrix used to reduce
         the full matrix to tridiagonal form.  QSIZ >= N if ICOMPQ = 1.

N

          N is INTEGER
         The dimension of the symmetric tridiagonal matrix.  N >= 0.

D

          D is DOUBLE PRECISION array, dimension (N)
         On entry, the diagonal elements of the tridiagonal matrix.
         On exit, the eigenvalues in ascending order.

E

          E is DOUBLE PRECISION array, dimension (N-1)
         On entry, the off-diagonal elements of the tridiagonal matrix.
         On exit, E has been destroyed.

Q

          Q is COMPLEX*16 array, dimension (LDQ,N)
         On entry, Q must contain an QSIZ x N matrix whose columns
         unitarily orthonormal. It is a part of the unitary matrix
         that reduces the full dense Hermitian matrix to a
         (reducible) symmetric tridiagonal matrix.

LDQ

          LDQ is INTEGER
         The leading dimension of the array Q.  LDQ >= max(1,N).

IWORK

          IWORK is INTEGER array,
         the dimension of IWORK must be at least
                      6 + 6*N + 5*N*lg N
                      ( lg( N ) = smallest integer k
                                  such that 2^k >= N )

RWORK

          RWORK is DOUBLE PRECISION array,
                               dimension (1 + 3*N + 2*N*lg N + 3*N**2)
                        ( lg( N ) = smallest integer k
                                    such that 2^k >= N )

QSTORE

          QSTORE is COMPLEX*16 array, dimension (LDQS, N)
         Used to store parts of
         the eigenvector matrix when the updating matrix multiplies
         take place.

LDQS

          LDQS is INTEGER
         The leading dimension of the array QSTORE.
         LDQS >= max(1,N).

INFO

          INFO is INTEGER
          = 0:  successful exit.
          < 0:  if INFO = -i, the i-th argument had an illegal value.
          > 0:  The algorithm failed to compute an eigenvalue while
                working on the submatrix lying in rows and columns
                INFO/(N+1) through mod(INFO,N+1).
Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

December 2016

Definition at line 147 of file zlaed0.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

The man page zlaed0(3) is an alias of zlaed0.f(3).

Sat Jun 24 2017 Version 3.7.1 LAPACK