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SparseLU_relax_snode.h
1 // This file is part of Eigen, a lightweight C++ template library
2 // for linear algebra.
3 //
4 // Copyright (C) 2012 Désiré Nuentsa-Wakam <[email protected]>
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 
46 template <typename Scalar, typename Index>
47 void 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