
SLAEDA(l) ) SLAEDA(l)
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 eigen
block.
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 subeigenvector matrix).
ZTEMP (workspace) REAL array, dimension (N)
INFO (output) INTEGER
= 0: successful exit.
< 0: if INFO = i, the ith argument had an illegal value.
FURTHER DETAILS
Based on contributions by
Jeff Rutter, Computer Science Division, University of California
at Berkeley, USA
LAPACK version 3.0 15 June 2000 SLAEDA(l) 
