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SUBROUTINE <a name="DLASDT.1"></a><a href="dlasdt.f.html#DLASDT.1">DLASDT</a>( N, LVL, ND, INODE, NDIML, NDIMR, MSUB )
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> -- LAPACK auxiliary routine (version 3.1) --
</span><span class="comment">*</span><span class="comment"> Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
</span><span class="comment">*</span><span class="comment"> November 2006
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Scalar Arguments ..
</span> INTEGER LVL, MSUB, N, ND
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Array Arguments ..
</span> INTEGER INODE( * ), NDIML( * ), NDIMR( * )
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Purpose
</span><span class="comment">*</span><span class="comment"> =======
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> <a name="DLASDT.17"></a><a href="dlasdt.f.html#DLASDT.1">DLASDT</a> creates a tree of subproblems for bidiagonal divide and
</span><span class="comment">*</span><span class="comment"> conquer.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Arguments
</span><span class="comment">*</span><span class="comment"> =========
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> N (input) INTEGER
</span><span class="comment">*</span><span class="comment"> On entry, the number of diagonal elements of the
</span><span class="comment">*</span><span class="comment"> bidiagonal matrix.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> LVL (output) INTEGER
</span><span class="comment">*</span><span class="comment"> On exit, the number of levels on the computation tree.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> ND (output) INTEGER
</span><span class="comment">*</span><span class="comment"> On exit, the number of nodes on the tree.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> INODE (output) INTEGER array, dimension ( N )
</span><span class="comment">*</span><span class="comment"> On exit, centers of subproblems.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> NDIML (output) INTEGER array, dimension ( N )
</span><span class="comment">*</span><span class="comment"> On exit, row dimensions of left children.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> NDIMR (output) INTEGER array, dimension ( N )
</span><span class="comment">*</span><span class="comment"> On exit, row dimensions of right children.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> MSUB (input) INTEGER.
</span><span class="comment">*</span><span class="comment"> On entry, the maximum row dimension each subproblem at the
</span><span class="comment">*</span><span class="comment"> bottom of the tree can be of.
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Further Details
</span><span class="comment">*</span><span class="comment"> ===============
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Based on contributions by
</span><span class="comment">*</span><span class="comment"> Ming Gu and Huan Ren, Computer Science Division, University of
</span><span class="comment">*</span><span class="comment"> California at Berkeley, USA
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> =====================================================================
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> .. Parameters ..
</span> DOUBLE PRECISION TWO
PARAMETER ( TWO = 2.0D+0 )
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Local Scalars ..
</span> INTEGER I, IL, IR, LLST, MAXN, NCRNT, NLVL
DOUBLE PRECISION TEMP
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Intrinsic Functions ..
</span> INTRINSIC DBLE, INT, LOG, MAX
<span class="comment">*</span><span class="comment"> ..
</span><span class="comment">*</span><span class="comment"> .. Executable Statements ..
</span><span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Find the number of levels on the tree.
</span><span class="comment">*</span><span class="comment">
</span> MAXN = MAX( 1, N )
TEMP = LOG( DBLE( MAXN ) / DBLE( MSUB+1 ) ) / LOG( TWO )
LVL = INT( TEMP ) + 1
<span class="comment">*</span><span class="comment">
</span> 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
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> Constructing the tree at (NLVL+1)-st level. The number of
</span><span class="comment">*</span><span class="comment"> nodes created on this level is LLST * 2.
</span><span class="comment">*</span><span class="comment">
</span> 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
<span class="comment">*</span><span class="comment">
</span> RETURN
<span class="comment">*</span><span class="comment">
</span><span class="comment">*</span><span class="comment"> End of <a name="DLASDT.103"></a><a href="dlasdt.f.html#DLASDT.1">DLASDT</a>
</span><span class="comment">*</span><span class="comment">
</span> END
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