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graph.hpp

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00001 /* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
00002 /*
00003  *  Main authors:
00004  *     Christian Schulte <schulte@gecode.org>
00005  *
00006  *  Copyright:
00007  *     Christian Schulte, 2003
00008  *
00009  *  This file is part of Gecode, the generic constraint
00010  *  development environment:
00011  *     http://www.gecode.org
00012  *
00013  *  Permission is hereby granted, free of charge, to any person obtaining
00014  *  a copy of this software and associated documentation files (the
00015  *  "Software"), to deal in the Software without restriction, including
00016  *  without limitation the rights to use, copy, modify, merge, publish,
00017  *  distribute, sublicense, and/or sell copies of the Software, and to
00018  *  permit persons to whom the Software is furnished to do so, subject to
00019  *  the following conditions:
00020  *
00021  *  The above copyright notice and this permission notice shall be
00022  *  included in all copies or substantial portions of the Software.
00023  *
00024  *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
00025  *  EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
00026  *  MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00027  *  NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
00028  *  LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
00029  *  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
00030  *  WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00031  *
00032  */
00033 
00034 #include <climits>
00035 
00036 namespace Gecode { namespace Int { namespace ViewValGraph {
00037 
00038   template<class View>
00039   forceinline
00040   Graph<View>::Graph(void)
00041     : view(NULL), val(NULL), n_view(0), n_val(0), count(1U) {}
00042 
00043   template<class View>
00044   forceinline
00045   Graph<View>::operator bool(void) const {
00046     return view != NULL;
00047   }
00048 
00049   template<class View>
00050   forceinline void
00051   Graph<View>::init(Space& home, ViewNode<View>* x) {
00052     Edge<View>** edge_p = x->val_edges_ref();
00053     ViewValues<View> xi(x->view());
00054     ValNode<View>** v = &val;
00055     while (xi() && (*v != NULL)) {
00056       if ((*v)->val() == xi.val()) {
00057         // Value node does already exist, create new edge
00058         *edge_p = new (home) Edge<View>(*v,x);
00059         edge_p = (*edge_p)->next_edge_ref();
00060         v = (*v)->next_val_ref();
00061         ++xi;
00062       } else if ((*v)->val() < xi.val()) {
00063         // Skip to next value node
00064         v = (*v)->next_val_ref();
00065       } else {
00066         // Value node does not yet exist, create and link it
00067         ValNode<View>* nv = new (home) ValNode<View>(xi.val(),*v);
00068         *v = nv; v = nv->next_val_ref();
00069         *edge_p = new (home) Edge<View>(nv,x);
00070         edge_p = (*edge_p)->next_edge_ref();
00071         ++xi; n_val++;
00072       }
00073     }
00074     // Create missing value nodes
00075     while (xi()) {
00076       ValNode<View>* nv = new (home) ValNode<View>(xi.val(),*v);
00077       *v = nv; v = nv->next_val_ref();
00078       *edge_p = new (home) Edge<View>(nv,x);
00079       edge_p = (*edge_p)->next_edge_ref();
00080       ++xi; n_val++;
00081     }
00082     *edge_p = NULL;
00083   }
00084 
00085   template<class View>
00086   forceinline bool
00087   Graph<View>::match(ViewNodeStack& m, ViewNode<View>* x) {
00088     count++;
00089   start:
00090     // Try to find matching edge cheaply: is there a free edge around?
00091     {
00092       Edge<View>* e = x->val_edges();
00093       // This holds true as domains are never empty
00094       assert(e != NULL);
00095       do {
00096         if (!e->val(x)->matching()) {
00097           e->revert(x); e->val(x)->matching(e);
00098           // Found a matching, revert all edges on stack
00099           while (!m.empty()) {
00100             x = m.pop(); e = x->iter;
00101             e->val(x)->matching()->revert(e->val(x));
00102             e->revert(x); e->val(x)->matching(e);
00103           }
00104           return true;
00105         }
00106         e = e->next_edge();
00107       } while (e != NULL);
00108     }
00109     // No, find matching edge by augmenting path method
00110     Edge<View>* e = x->val_edges();
00111     do {
00112       if (e->val(x)->matching()->view(e->val(x))->min < count) {
00113         e->val(x)->matching()->view(e->val(x))->min = count;
00114         m.push(x); x->iter = e;
00115         x = e->val(x)->matching()->view(e->val(x));
00116         goto start;
00117       }
00118     next:
00119       e = e->next_edge();
00120     } while (e != NULL);
00121     if (!m.empty()) {
00122       x = m.pop(); e = x->iter; goto next;
00123     }
00124     // All nodes and edges unsuccessfully tried
00125     return false;
00126   }
00127 
00128   template<class View>
00129   forceinline void
00130   Graph<View>::purge(void) {
00131     if (count > (UINT_MAX >> 1)) {
00132       count = 1;
00133       for (int i=0; i<n_view; i++)
00134         view[i]->min = 0;
00135       for (ValNode<View>* v = val; v != NULL; v = v->next_val())
00136         v->min = 0;
00137     }
00138   }
00139 
00140   template<class View>
00141   forceinline void
00142   Graph<View>::scc(void) {
00143     Region r;
00144 
00145     Support::StaticStack<Node<View>*,Region> scc(r,n_val+n_view);
00146     Support::StaticStack<Node<View>*,Region> visit(r,n_val+n_view);
00147 
00148     count++;
00149     unsigned int cnt0 = count;
00150     unsigned int cnt1 = count;
00151 
00152     for (int i=0; i<n_view; i++)
00153       /*
00154        * The following test is subtle: for scc, the test should be:
00155        *   view[i]->min < count
00156        * However, if view[i] < count-1, then the node has already been
00157        * reached on a path and all edges connected to the node have been
00158        * marked anyway! So just ignore this node altogether for scc.
00159        */
00160       if (view[i]->min < count-1) {
00161         Node<View>* w = view[i];
00162       start:
00163         w->low = w->min = cnt0++;
00164         scc.push(w);
00165         Edge<View>* e = w->edge_fst();
00166         while (e != w->edge_lst()) {
00167           if (e->dst(w)->min < count) {
00168             visit.push(w); w->iter = e;
00169             w=e->dst(w);
00170             goto start;
00171           }
00172         next:
00173           if (e->dst(w)->low < w->min)
00174             w->min = e->dst(w)->low;
00175           e = e->next();
00176         }
00177         if (w->min < w->low) {
00178           w->low = w->min;
00179         } else {
00180           Node<View>* v;
00181           do {
00182             v = scc.pop();
00183             v->comp = cnt1;
00184             v->low  = UINT_MAX;
00185           } while (v != w);
00186           cnt1++;
00187         }
00188         if (!visit.empty()) {
00189           w=visit.pop(); e=w->iter; goto next;
00190         }
00191       }
00192     count = cnt0+1;
00193   }
00194 
00195 
00196 }}}
00197 
00198 // STATISTICS: int-prop