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SUBROUTINE DLASDT( N, LVL, ND, INODE, NDIML, NDIMR, MSUB )
*
* -- LAPACK auxiliary routine (instrum to count ops, version 3.0) --
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
* Courant Institute, Argonne National Lab, and Rice University
* June 30, 1999
*
* .. Scalar Arguments ..
INTEGER LVL, MSUB, N, ND
* ..
* .. Array Arguments ..
INTEGER INODE( * ), NDIML( * ), NDIMR( * )
* ..
* Common block to return operation count
* .. Common blocks ..
COMMON / LATIME / OPS, ITCNT
* ..
* .. Scalars in Common ..
DOUBLE PRECISION ITCNT, OPS
* ..
*
* Purpose
* =======
*
* DLASDT creates a tree of subproblems for bidiagonal divide and
* conquer.
*
* Arguments
* =========
*
* N (input) INTEGER
* On entry, the number of diagonal elements of the
* bidiagonal matrix.
*
* LVL (output) INTEGER
* On exit, the number of levels on the computation tree.
*
* ND (output) INTEGER
* On exit, the number of nodes on the tree.
*
* INODE (output) INTEGER array, dimension ( N )
* On exit, centers of subproblems.
*
* NDIML (output) INTEGER array, dimension ( N )
* On exit, row dimensions of left children.
*
* NDIMR (output) INTEGER array, dimension ( N )
* On exit, row dimensions of right children.
*
* MSUB (input) INTEGER.
* On entry, the maximum row dimension each subproblem at the
* bottom of the tree can be of.
*
* Further Details
* ===============
*
* Based on contributions by
* Ming Gu and Huan Ren, Computer Science Division, University of
* California at Berkeley, USA
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION TWO
PARAMETER ( TWO = 2.0D0 )
* ..
* .. Local Scalars ..
INTEGER I, IL, IR, LLST, MAXN, NCRNT, NLVL
DOUBLE PRECISION TEMP
* ..
* .. Intrinsic Functions ..
INTRINSIC DBLE, INT, LOG, MAX
* ..
* .. Executable Statements ..
*
* Find the number of levels on the tree.
*
OPS = OPS + DBLE( 2 )
MAXN = MAX( 1, N )
TEMP = LOG( DBLE( MAXN ) / DBLE( MSUB+1 ) ) / LOG( TWO )
LVL = INT( TEMP ) + 1
*
I = N / 2
INODE( 1 ) = I + 1
NDIML( 1 ) = I
NDIMR( 1 ) = N - I - 1
IL = 0
IR = 1
LLST = 1
DO 20 NLVL = 1, LVL - 1
*
* Constructing the tree at (NLVL+1)-st level. The number of
* nodes created on this level is LLST * 2.
*
DO 10 I = 0, LLST - 1
IL = IL + 2
IR = IR + 2
NCRNT = LLST + I
NDIML( IL ) = NDIML( NCRNT ) / 2
NDIMR( IL ) = NDIML( NCRNT ) - NDIML( IL ) - 1
INODE( IL ) = INODE( NCRNT ) - NDIMR( IL ) - 1
NDIML( IR ) = NDIMR( NCRNT ) / 2
NDIMR( IR ) = NDIMR( NCRNT ) - NDIML( IR ) - 1
INODE( IR ) = INODE( NCRNT ) + NDIML( IR ) + 1
10 CONTINUE
LLST = LLST*2
20 CONTINUE
ND = LLST*2 - 1
*
RETURN
*
* End of DLASDT
*
END
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