CXML
        	    
LAPACK version 3.0
dlaeda(3)

PURPOSE
  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

SYNTAX
  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( * )

DESCRIPTION
  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.

FURTHER DETAILS
  Based on contributions by
     Jeff Rutter, Computer Science Division, University of California
     at Berkeley, USA