graph.hpp
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/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
/*
* Main authors:
* Christian Schulte <schulte@gecode.org>
*
* Copyright:
* Christian Schulte, 2011
*
* This file is part of Gecode, the generic constraint
* development environment:
* http://www.gecode.org
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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namespace Gecode { namespace Int { namespace NValues {
forceinline
Graph::Graph(void)
: n_matched(0) {}
forceinline int
Graph::size(void) const {
return n_matched;
}
forceinline void
Graph::init(Space& home, const ValSet& vs, const ViewArray<IntView>& x) {
using namespace ViewValGraph;
n_view = x.size() + vs.size();
view = home.alloc<ViewNode<IntView>*>(n_view);
// Create nodes corresponding to the value set vs
{
int i = x.size();
ValSet::Ranges vsr(vs);
ValNode<IntView>** v = &val;
for (Iter::Ranges::ToValues<ValSet::Ranges> n(vsr); n(); ++n) {
// Create view node
view[i] = new (home) ViewNode<IntView>();
// Create and link value node
ValNode<IntView>* nv = new (home) ValNode<IntView>(n.val());
*v = nv; v = nv->next_val_ref();
// Create and link single edge
Edge<IntView>** e = view[i]->val_edges_ref();
*e = new (home) Edge<IntView>(nv,view[i],NULL);
// Match edge
(*e)->revert(view[i]); nv->matching(*e);
i++;
}
*v = NULL;
n_val = vs.size();
n_matched = vs.size();
assert(i - x.size() == vs.size());
}
// Initialize real view nodes
for (int i=0; i<x.size(); i++) {
view[i] = new (home) ViewNode<IntView>(x[i]);
ViewValGraph::Graph<IntView>::init(home,view[i]);
}
// Match the real view nodes, if possible
Region r;
ViewNodeStack m(r,n_view);
for (int i=0; i<x.size(); i++)
if (match(m,view[i]))
n_matched++;
}
forceinline void
Graph::sync(void) {
using namespace ViewValGraph;
Region r;
// Whether to rematch
bool rematch = false;
// Synchronize nodes
for (int i=0; i<n_view; i++) {
ViewNode<IntView>* x = view[i];
// Skip faked view nodes, they correspond to values in the value set
if (!x->fake()) {
if (x->changed()) {
ViewRanges<IntView> rx(x->view());
Edge<IntView>* m = x->matched() ? x->edge_fst() : NULL;
Edge<IntView>** p = x->val_edges_ref();
Edge<IntView>* e = *p;
GECODE_ASSUME(e != NULL);
do {
while (e->val(x)->val() < rx.min()) {
// Skip edge
e->unlink(); e->mark();
e = e->next_edge();
}
*p = e;
assert(rx.min() == e->val(x)->val());
// This edges must be kept
for (unsigned int j=rx.width(); j--; ) {
e->free();
p = e->next_edge_ref();
e = e->next_edge();
}
++rx;
} while (rx());
*p = NULL;
while (e != NULL) {
e->unlink(); e->mark();
e = e->next_edge();
}
if ((m != NULL) && m->marked()) {
// Matching has been deleted!
m->val(x)->matching(NULL);
rematch = true;
n_matched--;
}
} else {
// Just free edges
for (Edge<IntView>* e=x->val_edges(); e != NULL; e = e->next_edge())
e->free();
}
}
}
if (rematch) {
ViewNodeStack m(r,n_view);
for (int i=0; i<n_view; i++)
if (!view[i]->matched() && match(m,view[i]))
n_matched++;
}
}
forceinline bool
Graph::mark(void) {
using namespace ViewValGraph;
Region r;
int n_view_visited = 0;
{
// Marks all edges as used that are on simple paths in the graph
// that start from a free value node by depth-first-search
Support::StaticStack<ValNode<IntView>*,Region> visit(r,n_val);
// Insert all free value nodes
count++;
{
ValNode<IntView>** v = &val;
while (*v != NULL)
// Is the node free?
if (!(*v)->matching()) {
// Eliminate empty value nodes
if ((*v)->empty()) {
*v = (*v)->next_val();
n_val--;
} else {
(*v)->min = count;
visit.push(*v);
v = (*v)->next_val_ref();
}
} else {
v = (*v)->next_val_ref();
}
}
// Invariant: only value nodes are on the stack!
while (!visit.empty()) {
ValNode<IntView>* n = visit.pop();
for (Edge<IntView>* e = n->edge_fst(); e != n->edge_lst();
e = e->next()) {
// Is the view node is matched: the path must be alternating!
ViewNode<IntView>* x = e->view(n);
if (x->matched()) {
// Mark the edge as used
e->use();
if (x->min < count) {
n_view_visited++;
x->min = count;
assert(x->edge_fst()->next() == x->edge_lst());
ValNode<IntView>* m = x->edge_fst()->val(x);
x->edge_fst()->use();
if (m->min < count) {
m->min = count;
visit.push(m);
}
}
}
}
}
}
if (n_view_visited < n_view) {
// Mark all edges as used starting from a free view node on
// an alternating path by depth-first search.
Support::StaticStack<ViewNode<IntView>*,Region> visit(r,n_view);
// Insert all free view nodes
count++;
for (int i=0; i<n_view; i++)
if (!view[i]->matched()) {
view[i]->min = count;
visit.push(view[i]);
}
// Invariant: only view nodes are on the stack!
while (!visit.empty()) {
n_view_visited++;
ViewNode<IntView>* x = visit.pop();
for (Edge<IntView>* e = x->val_edges(); e != NULL; e = e->next_edge())
// Consider only free edges
if (e != x->edge_fst()) {
ValNode<IntView>* n = e->val(x);
// Is there a matched edge from the value node to a view node?
if (n->matching() != NULL) {
e->use();
n->matching()->use();
ViewNode<IntView>* y = n->matching()->view(n);
if (y->min < count) {
y->min = count;
visit.push(y);
}
}
}
}
}
if (n_view_visited < n_view) {
scc();
return true;
} else {
return false;
}
}
forceinline ExecStatus
Graph::prune(Space& home) {
using namespace ViewValGraph;
// Tell constraints and also eliminate nodes and edges
for (int i = n_view; i--; ) {
ViewNode<IntView>* x = view[i];
if (!x->fake()) {
if (x->matched() && !x->edge_fst()->used(x)) {
GECODE_ME_CHECK(x->view().eq(home,x->edge_fst()->val(x)->val()));
x->edge_fst()->val(x)->matching(NULL);
for (Edge<IntView>* e = x->val_edges(); e != NULL; e=e->next_edge())
e->unlink();
view[i] = view[--n_view];
} else {
IterPruneVal<IntView> pv(x);
GECODE_ME_CHECK(x->view().minus_v(home,pv,false));
}
}
}
return ES_OK;
}
}}}
// STATISTICS: int-prop
Gecode::Int::NValues::Graph::init
void init(Space &home, const ValSet &vs, const ViewArray< IntView > &x)
Initialize graph including values in vs.
Definition graph.hpp:46
Gecode::Int::NValues::Graph::sync
void sync(void)
Synchronize graph with new view domains.
Definition graph.hpp:90
Gecode::Int::NValues::Graph::Graph
Graph(void)
Construct graph as not yet initialized.
Definition graph.hpp:37
Gecode::Int::NValues::Graph::mark
bool mark(void)
Definition graph.hpp:152
Gecode::Int::NValues::Graph::n_matched
int n_matched
Number of matched edges.
Definition nvalues.hh:99
Gecode::Int::NValues::Graph::prune
ExecStatus prune(Space &home)
Prune all values corresponding to unused edges.
Definition graph.hpp:255
Gecode::Int::NValues::Graph::size
int size(void) const
Return size of maximal matching (excluding assigned views).
Definition graph.hpp:41
Gecode::Int::ValSet::Ranges
Iterator over ranges.
Definition val-set.hh:78
Gecode::Int::ValSet
Class for storing values of already assigned views.
Definition val-set.hh:44
Gecode::Int::ValSet::size
int size(void) const
Return size (number of values).
Definition val-set.hpp:81
Gecode::Int::ViewRanges
Range iterator for integer views.
Definition view.hpp:54
Gecode::Int::ViewRanges::min
int min(void) const
Return smallest value of range.
Gecode::Int::ViewRanges::width
unsigned int width(void) const
Return width of range (distance between minimum and maximum).
Gecode::Int::ViewValGraph::Graph< IntView >::ViewNodeStack
Support::StaticStack< ViewNode< IntView > *, Region > ViewNodeStack
Definition view-val-graph.hh:307
Gecode::Int::ViewValGraph::Graph::init
void init(Space &home, ViewNode< View > *x)
Initialize the edges for the view node x.
Definition graph.hpp:51
Gecode::Int::ViewValGraph::Graph< IntView >::count
unsigned int count
Definition view-val-graph.hh:305
Gecode::Int::ViewValGraph::Graph< IntView >::view
ViewNode< IntView > ** view
Definition view-val-graph.hh:297
Gecode::Int::ViewValGraph::Graph< IntView >::match
bool match(ViewNodeStack &m, ViewNode< IntView > *x)
Definition graph.hpp:87
Gecode::Int::ViewValGraph::Graph< IntView >::n_view
int n_view
Definition view-val-graph.hh:301
Gecode::Int::ViewValGraph::Graph< IntView >::n_val
int n_val
Definition view-val-graph.hh:303
Gecode::Int::ViewValGraph::Graph< IntView >::scc
void scc(void)
Definition graph.hpp:142
Gecode::Int::ViewValGraph::Graph< IntView >::val
ValNode< IntView > * val
Definition view-val-graph.hh:299
Gecode::Iter::Ranges::ToValues
Value iterator from range iterator.
Definition ranges-values.hpp:42
Gecode::Region
Handle to region.
Definition region.hpp:55
Gecode::Space
Computation spaces.
Definition core.hpp:1742
Gecode::Space::alloc
T * alloc(long unsigned int n)
Allocate block of n objects of type T from space heap.
Definition core.hpp:2837
Gecode::Support::StaticStack
Stack with fixed number of elements.
Definition static-stack.hpp:42
Gecode::Support::StaticStack::push
void push(const T &x)
Push element x on top of stack.
Definition static-stack.hpp:137
Gecode::Support::StaticStack::pop
T pop(void)
Pop topmost element from stack and return it.
Definition static-stack.hpp:116
Gecode::Support::StaticStack::empty
bool empty(void) const
Test whether stack is empty.
Definition static-stack.hpp:98
Gecode::ViewArray
View arrays.
Definition array.hpp:253
Gecode::ViewArray::size
int size(void) const
Return size of array (number of elements).
Definition array.hpp:1156
GECODE_ME_CHECK
#define GECODE_ME_CHECK(me)
Check whether modification event me is failed, and forward failure.
Definition macros.hpp:52
Gecode::Int::NValues
Number of values propagators.
Gecode::Int::ViewValGraph
Support classes for propagators using a view-value graph.
Gecode::Int
Finite domain integers.
Gecode
Gecode toplevel namespace
Gecode::ExecStatus
ExecStatus
Definition core.hpp:472
Gecode::ES_OK
@ ES_OK
Execution is okay.
Definition core.hpp:476
forceinline
#define forceinline
Definition config.hpp:187
GECODE_ASSUME
#define GECODE_ASSUME(p)
Assert certain property.
Definition macros.hpp:114