slaeda(3F)

NAME
     SLAEDA - 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 SLAEDA( 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( * )

         REAL           GIVNUM( 2, * ), Q( * ), Z( * ), ZTEMP( * )

PURPOSE
     SLAEDA 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) REAL array, dimension (2, N lg N) Each number
            indicates the S value to be used in the corresponding Givens
            rotation.

     Q      (input) REAL 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) REAL 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) REAL array, dimension (N)

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