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dekker.one
1/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
2/*
3 * Main authors:
4 * Christian Schulte <schulte@gecode.org>
5 *
6 * Copyright:
7 * Christian Schulte, 2003
8 *
9 * This file is part of Gecode, the generic constraint
10 * development environment:
11 * http://www.gecode.org
12 *
13 * Permission is hereby granted, free of charge, to any person obtaining
14 * a copy of this software and associated documentation files (the
15 * "Software"), to deal in the Software without restriction, including
16 * without limitation the rights to use, copy, modify, merge, publish,
17 * distribute, sublicense, and/or sell copies of the Software, and to
18 * permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be
22 * included in all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
28 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
29 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
30 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 *
32 */
33
34#include <climits>
35
36namespace Gecode { namespace Int { namespace ViewValGraph {
37
38 template<class View>
39 forceinline
40 Graph<View>::Graph(void)
41 : view(nullptr), val(nullptr), n_view(0), n_val(0), count(1U) {}
42
43 template<class View>
44 forceinline
45 Graph<View>::operator bool(void) const {
46 return view != nullptr;
47 }
48
49 template<class View>
50 forceinline void
51 Graph<View>::init(Space& home, ViewNode<View>* x) {
52 Edge<View>** edge_p = x->val_edges_ref();
53 ViewValues<View> xi(x->view());
54 ValNode<View>** v = &val;
55 while (xi() && (*v != nullptr)) {
56 if ((*v)->val() == xi.val()) {
57 // Value node does already exist, create new edge
58 *edge_p = new (home) Edge<View>(*v,x);
59 edge_p = (*edge_p)->next_edge_ref();
60 v = (*v)->next_val_ref();
61 ++xi;
62 } else if ((*v)->val() < xi.val()) {
63 // Skip to next value node
64 v = (*v)->next_val_ref();
65 } else {
66 // Value node does not yet exist, create and link it
67 ValNode<View>* nv = new (home) ValNode<View>(xi.val(),*v);
68 *v = nv; v = nv->next_val_ref();
69 *edge_p = new (home) Edge<View>(nv,x);
70 edge_p = (*edge_p)->next_edge_ref();
71 ++xi; n_val++;
72 }
73 }
74 // Create missing value nodes
75 while (xi()) {
76 ValNode<View>* nv = new (home) ValNode<View>(xi.val(),*v);
77 *v = nv; v = nv->next_val_ref();
78 *edge_p = new (home) Edge<View>(nv,x);
79 edge_p = (*edge_p)->next_edge_ref();
80 ++xi; n_val++;
81 }
82 *edge_p = nullptr;
83 }
84
85 template<class View>
86 forceinline bool
87 Graph<View>::match(ViewNodeStack& m, ViewNode<View>* x) {
88 count++;
89 start:
90 // Try to find matching edge cheaply: is there a free edge around?
91 {
92 Edge<View>* e = x->val_edges();
93 // This holds true as domains are never empty
94 assert(e != nullptr);
95 do {
96 if (!e->val(x)->matching()) {
97 e->revert(x); e->val(x)->matching(e);
98 // Found a matching, revert all edges on stack
99 while (!m.empty()) {
100 x = m.pop(); e = x->iter;
101 e->val(x)->matching()->revert(e->val(x));
102 e->revert(x); e->val(x)->matching(e);
103 }
104 return true;
105 }
106 e = e->next_edge();
107 } while (e != nullptr);
108 }
109 // No, find matching edge by augmenting path method
110 Edge<View>* e = x->val_edges();
111 do {
112 if (e->val(x)->matching()->view(e->val(x))->min < count) {
113 e->val(x)->matching()->view(e->val(x))->min = count;
114 m.push(x); x->iter = e;
115 x = e->val(x)->matching()->view(e->val(x));
116 goto start;
117 }
118 next:
119 e = e->next_edge();
120 } while (e != nullptr);
121 if (!m.empty()) {
122 x = m.pop(); e = x->iter; goto next;
123 }
124 // All nodes and edges unsuccessfully tried
125 return false;
126 }
127
128 template<class View>
129 forceinline void
130 Graph<View>::purge(void) {
131 if (count > (UINT_MAX >> 1)) {
132 count = 1;
133 for (int i=0; i<n_view; i++)
134 view[i]->min = 0;
135 for (ValNode<View>* v = val; v != nullptr; v = v->next_val())
136 v->min = 0;
137 }
138 }
139
140 template<class View>
141 forceinline void
142 Graph<View>::scc(void) {
143 Region r;
144
145 Support::StaticStack<Node<View>*,Region> scc(r,n_val+n_view);
146 Support::StaticStack<Node<View>*,Region> visit(r,n_val+n_view);
147
148 count++;
149 unsigned int cnt0 = count;
150 unsigned int cnt1 = count;
151
152 for (int i=0; i<n_view; i++)
153 /*
154 * The following test is subtle: for scc, the test should be:
155 * view[i]->min < count
156 * However, if view[i] < count-1, then the node has already been
157 * reached on a path and all edges connected to the node have been
158 * marked anyway! So just ignore this node altogether for scc.
159 */
160 if (view[i]->min < count-1) {
161 Node<View>* w = view[i];
162 start:
163 w->low = w->min = cnt0++;
164 scc.push(w);
165 Edge<View>* e = w->edge_fst();
166 while (e != w->edge_lst()) {
167 if (e->dst(w)->min < count) {
168 visit.push(w); w->iter = e;
169 w=e->dst(w);
170 goto start;
171 }
172 next:
173 if (e->dst(w)->low < w->min)
174 w->min = e->dst(w)->low;
175 e = e->next();
176 }
177 if (w->min < w->low) {
178 w->low = w->min;
179 } else {
180 Node<View>* v;
181 do {
182 v = scc.pop();
183 v->comp = cnt1;
184 v->low = UINT_MAX;
185 } while (v != w);
186 cnt1++;
187 }
188 if (!visit.empty()) {
189 w=visit.pop(); e=w->iter; goto next;
190 }
191 }
192 count = cnt0+1;
193 }
194
195
196}}}
197
198// STATISTICS: int-prop