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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( * )



     #include <sunperf.h>

     void dlaeda(int n, int tlvls, int curlvl,  int  curpbm,  int
               *prmptr, int *perm, int *givptr, int *givcol, dou-
               ble *givnum, double *q,  int  *qptr,  double  *dz,
               double *ztemp, int *info) ;

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 (count-
               ing 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 lev-
               els,  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 ille-
               gal value.

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