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
31 namespace Eigen {
32
33 namespace 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 */
46 template <typename Scalar, typename StorageIndex>
relax_snode(const Index n,IndexVector & et,const Index relax_columns,IndexVector & descendants,IndexVector & relax_end)47 void SparseLUImpl<Scalar,StorageIndex>::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 parent;
52 relax_end.setConstant(emptyIdxLU);
53 descendants.setZero();
54 for (Index 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 (Index 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) = StorageIndex(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