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Reduce difference logic solver to min cost flow

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Anh-Dung Phan 2013-10-25 17:42:03 -07:00
parent ebed5fa037
commit 532c345fd1
5 changed files with 152 additions and 65 deletions
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33
src/smt/network_flow.h
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@ -38,31 +38,29 @@ namespace smt {
// Solve minimum cost flow problem using Network Simplex algorithm
template<typename Ext>
class network_flow : private Ext {
struct GExt : public Ext {
typedef literal explanation;
};
typedef dl_var node;
typedef dl_edge<GExt> edge;
typedef dl_graph<GExt> graph;
typedef typename Ext::numeral numeral;
typedef dl_edge<Ext> edge;
typedef dl_graph<Ext> graph;
typedef typename Ext::numeral numeral;
graph m_graph;
// Denote supply/demand b_i on node i
vector<numeral> m_balances;
// Duals of flows which are convenient to compute dual solutions
vector<numeral> m_potentials;
// Keep optimal solution of the min cost flow problem
inf_rational m_objective;
// Costs on edges
vector<numeral> & m_costs;
// Basic feasible flows
vector<numeral> m_flows;
// Denote the spanning tree of basic edges
vector<edge> m_basics;
// Denote non-basic edges with flow 0 for uncapicitated networks
vector<edge> m_nonbasics;
// An element is true if the corresponding edge points upwards (compared to the root node)
svector<bool> m_upwards;
// Store the parent of a node in the spanning tree
svector<node> m_pred;
@ -71,7 +69,12 @@ namespace smt {
// Store the pointer to the next node in depth first search ordering
svector<node> m_thread;
bool m_is_optimal;
public:
network_flow(graph & g, vector<numeral> & costs);
// Initialize the network with a feasible spanning tree
void initialize();
@ -81,13 +84,13 @@ namespace smt {
// If all reduced costs are non-negative, the current flow is optimal
// If not optimal, return a violating edge in the corresponding variable
bool is_optimal(edge & violating_edge);
bool is_optimal(edge_id & violating_edge);
// Send as much flow as possible around the cycle, the first basic edge with flow 0 will leave
edge choose_leaving_edge(const edge & entering_edge);
void update_basics(const edge & entering_edge, const edge & leaving_edge);
edge_id choose_leaving_edge(edge_id entering_edge);
void update_spanning_tree(edge_id entering_edge, edge_id leaving_edge);
bool is_unbounded();
// Compute the optimal solution