dlaeda(3F)

NAME
     DLAEDA - compute the Z vector corresponding to the merge step in the
     CURLVLth step of the merge process with TLVLS steps for the CURPBMth
     problem

SYNOPSIS
     SUBROUTINE DLAEDA( N, TLVLS, CURLVL, CURPBM, PRMPTR, PERM, GIVPTR,
                        GIVCOL, GIVNUM, Q, QPTR, Z, ZTEMP, INFO )

         INTEGER        CURLVL, CURPBM, INFO, N, TLVLS

         INTEGER        GIVCOL( 2, * ), GIVPTR( * ), PERM( * ), PRMPTR( * ),
                        QPTR( * )

         DOUBLE         PRECISION GIVNUM( 2, * ), Q( * ), Z( * ), ZTEMP( * )

PURPOSE
     DLAEDA computes the Z vector corresponding to the merge step in the
     CURLVLth step of the merge process with TLVLS steps for the CURPBMth
     problem.


ARGUMENTS
     N      (input) INTEGER
            The dimension of the symmetric tridiagonal matrix.  N >= 0.

     TLVLS  (input) INTEGER
            The total number of merging levels in the overall divide and
            conquer tree.

            CURLVL (input) INTEGER The current level in the overall merge
            routine, 0 <= curlvl <= tlvls.

            CURPBM (input) INTEGER The current problem in the current level in
            the overall merge routine (counting from upper left to lower
            right).

            PRMPTR (input) INTEGER array, dimension (N lg N) Contains a list
            of pointers which indicate where in PERM a level's permutation is
            stored.  PRMPTR(i+1) - PRMPTR(i) indicates the size of the
            permutation and incidentally the size of the full, non-deflated
            problem.

     PERM   (input) INTEGER array, dimension (N lg N)
            Contains the permutations (from deflation and sorting) to be
            applied to each eigenblock.

            GIVPTR (input) INTEGER array, dimension (N lg N) Contains a list
            of pointers which indicate where in GIVCOL a level's Givens
            rotations are stored.  GIVPTR(i+1) - GIVPTR(i) indicates the
            number of Givens rotations.
            GIVCOL (input) INTEGER array, dimension (2, N lg N) Each pair of
            numbers indicates a pair of columns to take place in a Givens
            rotation.

            GIVNUM (input) DOUBLE PRECISION array, dimension (2, N lg N) Each
            number indicates the S value to be used in the corresponding
            Givens rotation.

     Q      (input) DOUBLE PRECISION array, dimension (N**2)
            Contains the square eigenblocks from previous levels, the starting
            positions for blocks are given by QPTR.

     QPTR   (input) INTEGER array, dimension (N+2)
            Contains a list of pointers which indicate where in Q an
            eigenblock is stored.  SQRT( QPTR(i+1) - QPTR(i) ) indicates the
            size of the block.

     Z      (output) DOUBLE PRECISION array, dimension (N)
            On output this vector contains the updating vector (the last row
            of the first sub-eigenvector matrix and the first row of the
            second sub-eigenvector matrix).

     ZTEMP  (workspace) DOUBLE PRECISION array, dimension (N)

     INFO   (output) INTEGER
            = 0:  successful exit.
            < 0:  if INFO = -i, the i-th argument had an illegal value.