1// This file is part of Eigen, a lightweight C++ template library
2// for linear algebra.
3//
4// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
5//
6// This Source Code Form is subject to the terms of the Mozilla
7// Public License v. 2.0. If a copy of the MPL was not distributed
8// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
9
10/* This file is a modified version of heap_relax_snode.c file in SuperLU
11 * -- SuperLU routine (version 3.0) --
12 * Univ. of California Berkeley, Xerox Palo Alto Research Center,
13 * and Lawrence Berkeley National Lab.
14 * October 15, 2003
15 *
16 * Copyright (c) 1994 by Xerox Corporation.  All rights reserved.
17 *
18 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
19 * EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
20 *
21 * Permission is hereby granted to use or copy this program for any
22 * purpose, provided the above notices are retained on all copies.
23 * Permission to modify the code and to distribute modified code is
24 * granted, provided the above notices are retained, and a notice that
25 * the code was modified is included with the above copyright notice.
26 */
27
28#ifndef SPARSELU_RELAX_SNODE_H
29#define SPARSELU_RELAX_SNODE_H
30
31namespace Eigen {
32
33namespace internal {
34
35/**
36 * \brief Identify the initial relaxed supernodes
37 *
38 * This routine is applied to a column elimination tree.
39 * It assumes that the matrix has been reordered according to the postorder of the etree
40 * \param n  the number of columns
41 * \param et elimination tree
42 * \param relax_columns Maximum number of columns allowed in a relaxed snode
43 * \param descendants Number of descendants of each node in the etree
44 * \param relax_end last column in a supernode
45 */
46template <typename Scalar, typename Index>
47void SparseLUImpl<Scalar,Index>::relax_snode (const Index n, IndexVector& et, const Index relax_columns, IndexVector& descendants, IndexVector& relax_end)
48{
49
50  // compute the number of descendants of each node in the etree
51  Index j, parent;
52  relax_end.setConstant(emptyIdxLU);
53  descendants.setZero();
54  for (j = 0; j < n; j++)
55  {
56    parent = et(j);
57    if (parent != n) // not the dummy root
58      descendants(parent) += descendants(j) + 1;
59  }
60  // Identify the relaxed supernodes by postorder traversal of the etree
61  Index snode_start; // beginning of a snode
62  for (j = 0; j < n; )
63  {
64    parent = et(j);
65    snode_start = j;
66    while ( parent != n && descendants(parent) < relax_columns )
67    {
68      j = parent;
69      parent = et(j);
70    }
71    // Found a supernode in postordered etree, j is the last column
72    relax_end(snode_start) = j; // Record last column
73    j++;
74    // Search for a new leaf
75    while (descendants(j) != 0 && j < n) j++;
76  } // End postorder traversal of the etree
77
78}
79
80} // end namespace internal
81
82} // end namespace Eigen
83#endif
84