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Implement three pivot rules

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Anh-Dung Phan 2013-11-11 08:51:52 +01:00
parent e412d6175d
commit 0d6ffe6b31
3 changed files with 226 additions and 48 deletions
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45
src/smt/network_flow_def.h
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@ -129,30 +129,6 @@ namespace smt {
TRACE("network_flow", tout << pp_vector("Flows", m_flows, true););
}
template<typename Ext>
bool network_flow<Ext>::choose_entering_edge() {
TRACE("network_flow", tout << "choose_entering_edge...\n";);
unsigned num_edges = m_graph.get_num_edges();
for (unsigned i = 0; i < num_edges; ++i) {
node src = m_graph.get_source(i);
node tgt = m_graph.get_target(i);
if (m_states[i] != BASIS) {
numeral cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(i);
// TODO: add multiple pivoting strategies
if (cost.is_pos()) {
m_enter_id = i;
TRACE("network_flow", {
tout << "Found entering edge " << i << " between node ";
tout << src << " and node " << tgt << " with reduced cost = " << cost << "...\n";
});
return true;
}
}
}
TRACE("network_flow", tout << "Found no entering edge...\n";);
return false;
}
template<typename Ext>
bool network_flow<Ext>::choose_leaving_edge() {
TRACE("network_flow", tout << "choose_leaving_edge...\n";);
@ -191,12 +167,29 @@ namespace smt {
m_tree.update(m_enter_id, m_leave_id);
}
// FIXME: should declare pivot as a pivot_rule_impl and refactor
template<typename Ext>
bool network_flow<Ext>::choose_entering_edge(pivot_rule pr) {
if (pr == FIRST_ELIGIBLE) {
first_eligible_pivot pivot(m_graph, m_potentials, m_states, m_enter_id);
return pivot.choose_entering_edge();
}
else if (pr == BEST_ELIGIBLE) {
best_eligible_pivot pivot(m_graph, m_potentials, m_states, m_enter_id);
return pivot.choose_entering_edge();
}
else {
candidate_list_pivot pivot(m_graph, m_potentials, m_states, m_enter_id);
return pivot.choose_entering_edge();
}
}
// Minimize cost flows
// Return true if found an optimal solution, and return false if unbounded
template<typename Ext>
bool network_flow<Ext>::min_cost() {
bool network_flow<Ext>::min_cost(pivot_rule pr) {
initialize();
while (choose_entering_edge()) {
while (choose_entering_edge(pr)) {
bool bounded = choose_leaving_edge();
if (!bounded) return false;
update_flows();