SLAEDA(3)      LAPACK routine of NEC Numeric Library Collection      SLAEDA(3)



NAME
       SLAEDA

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



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)
                     N is INTEGER
                    The dimension of the symmetric tridiagonal matrix.  N >= 0.

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

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

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

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

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

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

           QPTR      (input)
                     QPTR is 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)
                     Z is 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     (output)
                     ZTEMP is REAL array, dimension (N)

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



LAPACK routine                  31 October 2017                      SLAEDA(3)