LAPACK  3.4.1
LAPACK: Linear Algebra PACKage
dlasdt.f
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00001 *> \brief \b DLASDT
00002 *
00003 *  =========== DOCUMENTATION ===========
00004 *
00005 * Online html documentation available at 
00006 *            http://www.netlib.org/lapack/explore-html/ 
00007 *
00008 *> \htmlonly
00009 *> Download DLASDT + dependencies 
00010 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlasdt.f"> 
00011 *> [TGZ]</a> 
00012 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlasdt.f"> 
00013 *> [ZIP]</a> 
00014 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlasdt.f"> 
00015 *> [TXT]</a>
00016 *> \endhtmlonly 
00017 *
00018 *  Definition:
00019 *  ===========
00020 *
00021 *       SUBROUTINE DLASDT( N, LVL, ND, INODE, NDIML, NDIMR, MSUB )
00022 * 
00023 *       .. Scalar Arguments ..
00024 *       INTEGER            LVL, MSUB, N, ND
00025 *       ..
00026 *       .. Array Arguments ..
00027 *       INTEGER            INODE( * ), NDIML( * ), NDIMR( * )
00028 *       ..
00029 *  
00030 *
00031 *> \par Purpose:
00032 *  =============
00033 *>
00034 *> \verbatim
00035 *>
00036 *> DLASDT creates a tree of subproblems for bidiagonal divide and
00037 *> conquer.
00038 *> \endverbatim
00039 *
00040 *  Arguments:
00041 *  ==========
00042 *
00043 *> \param[in] N
00044 *> \verbatim
00045 *>          N is INTEGER
00046 *>          On entry, the number of diagonal elements of the
00047 *>          bidiagonal matrix.
00048 *> \endverbatim
00049 *>
00050 *> \param[out] LVL
00051 *> \verbatim
00052 *>          LVL is INTEGER
00053 *>          On exit, the number of levels on the computation tree.
00054 *> \endverbatim
00055 *>
00056 *> \param[out] ND
00057 *> \verbatim
00058 *>          ND is INTEGER
00059 *>          On exit, the number of nodes on the tree.
00060 *> \endverbatim
00061 *>
00062 *> \param[out] INODE
00063 *> \verbatim
00064 *>          INODE is INTEGER array, dimension ( N )
00065 *>          On exit, centers of subproblems.
00066 *> \endverbatim
00067 *>
00068 *> \param[out] NDIML
00069 *> \verbatim
00070 *>          NDIML is INTEGER array, dimension ( N )
00071 *>          On exit, row dimensions of left children.
00072 *> \endverbatim
00073 *>
00074 *> \param[out] NDIMR
00075 *> \verbatim
00076 *>          NDIMR is INTEGER array, dimension ( N )
00077 *>          On exit, row dimensions of right children.
00078 *> \endverbatim
00079 *>
00080 *> \param[in] MSUB
00081 *> \verbatim
00082 *>          MSUB is INTEGER
00083 *>          On entry, the maximum row dimension each subproblem at the
00084 *>          bottom of the tree can be of.
00085 *> \endverbatim
00086 *
00087 *  Authors:
00088 *  ========
00089 *
00090 *> \author Univ. of Tennessee 
00091 *> \author Univ. of California Berkeley 
00092 *> \author Univ. of Colorado Denver 
00093 *> \author NAG Ltd. 
00094 *
00095 *> \date November 2011
00096 *
00097 *> \ingroup auxOTHERauxiliary
00098 *
00099 *> \par Contributors:
00100 *  ==================
00101 *>
00102 *>     Ming Gu and Huan Ren, Computer Science Division, University of
00103 *>     California at Berkeley, USA
00104 *>
00105 *  =====================================================================
00106       SUBROUTINE DLASDT( N, LVL, ND, INODE, NDIML, NDIMR, MSUB )
00107 *
00108 *  -- LAPACK auxiliary routine (version 3.4.0) --
00109 *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
00110 *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
00111 *     November 2011
00112 *
00113 *     .. Scalar Arguments ..
00114       INTEGER            LVL, MSUB, N, ND
00115 *     ..
00116 *     .. Array Arguments ..
00117       INTEGER            INODE( * ), NDIML( * ), NDIMR( * )
00118 *     ..
00119 *
00120 *  =====================================================================
00121 *
00122 *     .. Parameters ..
00123       DOUBLE PRECISION   TWO
00124       PARAMETER          ( TWO = 2.0D+0 )
00125 *     ..
00126 *     .. Local Scalars ..
00127       INTEGER            I, IL, IR, LLST, MAXN, NCRNT, NLVL
00128       DOUBLE PRECISION   TEMP
00129 *     ..
00130 *     .. Intrinsic Functions ..
00131       INTRINSIC          DBLE, INT, LOG, MAX
00132 *     ..
00133 *     .. Executable Statements ..
00134 *
00135 *     Find the number of levels on the tree.
00136 *
00137       MAXN = MAX( 1, N )
00138       TEMP = LOG( DBLE( MAXN ) / DBLE( MSUB+1 ) ) / LOG( TWO )
00139       LVL = INT( TEMP ) + 1
00140 *
00141       I = N / 2
00142       INODE( 1 ) = I + 1
00143       NDIML( 1 ) = I
00144       NDIMR( 1 ) = N - I - 1
00145       IL = 0
00146       IR = 1
00147       LLST = 1
00148       DO 20 NLVL = 1, LVL - 1
00149 *
00150 *        Constructing the tree at (NLVL+1)-st level. The number of
00151 *        nodes created on this level is LLST * 2.
00152 *
00153          DO 10 I = 0, LLST - 1
00154             IL = IL + 2
00155             IR = IR + 2
00156             NCRNT = LLST + I
00157             NDIML( IL ) = NDIML( NCRNT ) / 2
00158             NDIMR( IL ) = NDIML( NCRNT ) - NDIML( IL ) - 1
00159             INODE( IL ) = INODE( NCRNT ) - NDIMR( IL ) - 1
00160             NDIML( IR ) = NDIMR( NCRNT ) / 2
00161             NDIMR( IR ) = NDIMR( NCRNT ) - NDIML( IR ) - 1
00162             INODE( IR ) = INODE( NCRNT ) + NDIML( IR ) + 1
00163    10    CONTINUE
00164          LLST = LLST*2
00165    20 CONTINUE
00166       ND = LLST*2 - 1
00167 *
00168       RETURN
00169 *
00170 *     End of DLASDT
00171 *
00172       END
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