mirror of
https://github.com/Z3Prover/z3
synced 2025-04-22 16:45:31 +00:00
Add pretty printing for network_flow
Reuse the original graph as much as possible
This commit is contained in:
Anh-Dung Phan
parent
1878d64b02
commit
905f230b8f
4 changed files with 190 additions and 67 deletions
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@ -281,6 +281,8 @@ public:
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unsigned get_num_edges() const { return m_edges.size(); }
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unsigned get_num_nodes() const { return m_out_edges.size(); }
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dl_var get_source(edge_id id) const { return m_edges[id].get_source(); }
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dl_var get_target(edge_id id) const { return m_edges[id].get_target(); }
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@ -47,7 +47,7 @@ namespace smt {
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typedef dl_graph<Ext> graph;
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typedef typename Ext::numeral numeral;
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typedef typename Ext::fin_numeral fin_numeral;
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graph m_graph;
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graph & m_graph;
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// Denote supply/demand b_i on node i
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vector<fin_numeral> m_balances;
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@ -57,10 +57,7 @@ namespace smt {
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// Keep optimal solution of the min cost flow problem
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numeral m_objective_value;
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// Costs on edges
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vector<fin_numeral> m_costs;
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// Basic feasible flows
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vector<numeral> m_flows;
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@ -79,18 +76,12 @@ namespace smt {
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svector<node> m_rev_thread;
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// Store a final node of the sub tree rooted at node i
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svector<node> m_final;
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// Number of nodes in the sub tree rooted at node i
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svector<int> m_num_node;
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edge_id m_entering_edge;
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edge_id m_leaving_edge;
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node m_join_node;
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numeral m_delta;
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public:
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network_flow(graph & g, vector<fin_numeral> const & balances);
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// Initialize the network with a feasible spanning tree
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void initialize();
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@ -107,13 +98,21 @@ namespace smt {
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bool choose_leaving_edge();
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void update_spanning_tree();
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// Compute the optimal solution
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numeral get_optimal_solution(vector<numeral> & result, bool is_dual);
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std::string pp_vector(std::string const & label, svector<int> v, bool has_header = false);
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std::string pp_vector(std::string const & label, vector<numeral> v, bool has_header = false);
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public:
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network_flow(graph & g, vector<fin_numeral> const & balances);
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// Minimize cost flows
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// Return true if found an optimal solution, and return false if unbounded
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bool min_cost();
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// Compute the optimal solution
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numeral get_optimal_solution(vector<numeral> & result, bool is_dual);
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};
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}
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@ -25,25 +25,15 @@ Notes:
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namespace smt {
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template<typename Ext>
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network_flow<Ext>::network_flow(graph & g, vector<fin_numeral> const& balances) :
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network_flow<Ext>::network_flow(graph & g, vector<fin_numeral> const & balances) :
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m_graph(g),
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m_balances(balances) {
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unsigned num_nodes = m_balances.size() + 1;
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unsigned num_nodes = m_graph.get_num_nodes() + 1;
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unsigned num_edges = m_graph.get_num_edges();
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vector<edge> const & es = m_graph.get_all_edges();
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for (unsigned i = 0; i < num_edges; ++i) {
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fin_numeral cost(es[i].get_weight().get_rational());
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m_costs.push_back(cost);
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}
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m_balances.resize(num_nodes);
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for (unsigned i = 0; i < balances.size(); ++i) {
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m_costs.push_back(balances[i]);
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}
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m_potentials.resize(num_nodes);
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m_costs.resize(num_edges);
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m_potentials.resize(num_nodes);
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m_flows.resize(num_edges);
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m_states.resize(num_edges);
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@ -53,19 +43,18 @@ namespace smt {
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m_thread.resize(num_nodes);
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m_rev_thread.resize(num_nodes);
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m_final.resize(num_nodes);
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m_num_node.resize(num_nodes);
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}
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template<typename Ext>
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void network_flow<Ext>::initialize() {
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TRACE("network_flow", tout << "initialize...\n";);
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// Create an artificial root node to construct initial spanning tree
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unsigned num_nodes = m_balances.size();
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unsigned num_nodes = m_graph.get_num_nodes();
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unsigned num_edges = m_graph.get_num_edges();
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node root = num_nodes;
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m_pred[root] = -1;
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m_thread[root] = 0;
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m_rev_thread[0] = root;
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m_num_node[root] = num_nodes + 1;
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m_final[root] = root - 1;
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m_potentials[root] = numeral::zero();
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@ -85,14 +74,17 @@ namespace smt {
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m_depth[i] = 1;
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m_thread[i] = i + 1;
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m_final[i] = i;
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m_rev_thread[i] = (i = 0) ? root : i - 1;
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m_num_node[i] = 1;
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m_rev_thread[i] = (i == 0) ? root : i - 1;
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m_states[num_edges + i] = BASIS;
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}
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TRACE("network_flow", tout << pp_vector("Predecessors", m_pred, true) << pp_vector("Threads", m_thread)
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<< pp_vector("Reverse Threads", m_rev_thread) << pp_vector("Last Successors", m_final) << pp_vector("Depths", m_depth););
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}
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template<typename Ext>
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void network_flow<Ext>::update_potentials() {
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TRACE("network_flow", tout << "update_potentials...\n";);
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node src = m_graph.get_source(m_entering_edge);
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node tgt = m_graph.get_source(m_entering_edge);
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numeral cost = m_graph.get_weight(m_entering_edge);
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@ -102,31 +94,37 @@ namespace smt {
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for (node u = src; u != last; u = m_thread[u]) {
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m_potentials[u] += change;
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}
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TRACE("network_flow", tout << pp_vector("Potentials", m_potentials, true););
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}
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template<typename Ext>
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void network_flow<Ext>::update_flows() {
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TRACE("network_flow", tout << "update_flows...\n";);
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numeral val = m_state[m_entering_edge] == NON_BASIS ? numeral::zero() : m_delta;
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m_flows[m_entering_edge] += val;
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for (unsigned u = m_graph.get_source(m_entering_edge); u != m_join_node; u = m_pred[u]) {
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node source = m_graph.get_source(m_entering_edge);
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for (unsigned u = source; u != m_join_node; u = m_pred[u]) {
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edge_id e_id;
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m_graph.get_edge_id(u, m_pred[u], e_id);
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m_flows[e_id] += m_upwards[u] ? -val : val;
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}
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for (unsigned u = m_graph.get_target(m_entering_edge); u != m_join_node; u = m_pred[u]) {
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node target = m_graph.get_target(m_entering_edge);
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for (unsigned u = target; u != m_join_node; u = m_pred[u]) {
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edge_id e_id;
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m_graph.get_edge_id(u, m_pred[u], e_id);
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m_flows[e_id] += m_upwards[u] ? val : -val;
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}
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TRACE("network_flow", tout << pp_vector("Flows", m_flows, true););
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}
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template<typename Ext>
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bool network_flow<Ext>::choose_entering_edge() {
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TRACE("network_flow", tout << "choose_entering_edge...\n";);
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vector<edge> const & es = m_graph.get_all_edges();
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for (unsigned int i = 0; i < es.size(); ++i) {
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edge const & e = es[i];
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edge_id e_id;
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if (e.is_enabled() && m_graph.get_edge_id(e.get_source(), e.get_target(), e_id) && m_states[e_id] == BASIS) {
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if (e.is_enabled() && m_graph.get_edge_id(e.get_source(), e.get_target(), e_id) && m_states[e_id] == NON_BASIS) {
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node source = e.get_source();
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node target = e.get_target();
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numeral cost = e.get_weight() - m_potentials[source] + m_potentials[target];
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@ -134,15 +132,18 @@ namespace smt {
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// TODO: add multiple pivoting strategies
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if (cost < numeral::zero()) {
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m_entering_edge = e_id;
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TRACE("network_flow", tout << "Found entering edge " << e_id << " between node " << source << " and node " << target << "...\n";);
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return true;
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}
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}
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}
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TRACE("network_flow", tout << "Found no entering edge... It's probably optimal.\n";);
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return false;
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}
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template<typename Ext>
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bool network_flow<Ext>::choose_leaving_edge() {
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TRACE("network_flow", tout << "choose_leaving_edge...\n";);
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node source = m_graph.get_source(m_entering_edge);
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node target = m_graph.get_target(m_entering_edge);
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node u = source, v = target;
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@ -158,9 +159,9 @@ namespace smt {
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}
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// Found first common ancestor of source and target
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m_join_node = u;
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// FIXME: need to get truly finite value
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// FIXME: need to get truly infinite value
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numeral infty = numeral(INT_MAX);
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m_delta = infty;
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m_delta = infty;
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node src, tgt;
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// Send flows along the path from source to the ancestor
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for (unsigned u = source; u != m_join_node; u = m_pred[u]) {
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@ -188,31 +189,143 @@ namespace smt {
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if (m_delta < infty) {
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m_graph.get_edge_id(src, tgt, m_leaving_edge);
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TRACE("network_flow", tout << "Found leaving edge" << m_leaving_edge << "between node " << src << " and node " << tgt << "...\n";);
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return true;
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}
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TRACE("network_flow", tout << "Can't find a leaving edge... The problem is unbounded.\n";);
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return false;
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}
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template<typename Ext>
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void network_flow<Ext>::update_spanning_tree() {
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void network_flow<Ext>::update_spanning_tree() {
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node src_in = m_graph.get_source(m_entering_edge);
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node tgt_in = m_graph.get_target(m_entering_edge);
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node src_out = m_graph.get_source(m_leaving_edge);
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node tgt_out = m_graph.get_target(m_leaving_edge);
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TRACE("network_flow", tout << "update_spanning_tree: (" << src_in << ", " << tgt_in << ") enters, ("
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<< src_out << ", " << tgt_out << ") leaves\n";);
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node root = m_graph.get_num_nodes();
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node rev_thread_out = m_rev_thread[src_out];
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node x = m_final[src_in];
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node y = m_thread[x];
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node z = m_final[src_out];
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// Update m_pred (for nodes in the stem from tgt_in to tgt_out)
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node u = tgt_in;
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node last = m_pred[tgt_out];
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node parent = src_in;
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while (u != last) {
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node next = m_pred[u];
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m_pred[u] = parent;
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u = next;
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}
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// Graft T_q and T_r'
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m_thread[x] = src_out;
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m_thread[z] = y;
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u = src_out;
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while (u != m_final[src_out]) {
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m_depth[u] += 1 + m_depth[src_in];
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u = m_pred[u];
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}
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node gamma = m_thread[m_final[src_in]];
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last = m_pred[gamma] != 0 ? gamma : root;
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for (node u = src_in; u == last; u = m_pred[u]) {
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m_final[u] = z;
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}
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// Update T_r'
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node phi = m_thread[tgt_out];
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node theta = m_thread[m_final[tgt_out]];
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m_thread[phi] = theta;
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gamma = m_thread[m_final[tgt_out]];
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// REVIEW: check f(u) is not in T_v
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node delta = m_final[src_out] != m_final[tgt_out] ? m_final[src_out] : m_rev_thread[tgt_out];
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last = m_pred[gamma] != 0 ? gamma : root;
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for (node u = src_in; u == last; u = m_pred[u]) {
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m_final[u] = delta;
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}
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// Reroot T_v at q
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if (src_out != tgt_in) {
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node u = m_pred[src_out];
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m_thread[m_final[src_out]] = u;
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last = tgt_in;
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node alpha1, alpha2;
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unsigned count = 0;
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while (u != last) {
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// Find all immediate successors of u
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node t1 = m_thread[u];
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node t2 = m_thread[m_final[t1]];
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node t3 = m_thread[m_final[t2]];
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if (t1 = m_pred[u]) {
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alpha1 = t2;
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alpha2 = t3;
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}
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else if (t2 = m_pred[u]) {
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alpha1 = t1;
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alpha2 = t3;
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}
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else {
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alpha1 = t1;
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alpha2 = t2;
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}
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m_thread[u] = alpha1;
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m_thread[m_final[alpha1]] = alpha2;
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u = m_pred[u];
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m_thread[m_final[alpha2]] = u;
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// Decrease depth of all children in the subtree
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++count;
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int d = m_depth[u] - count;
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for (node v = m_thread[u]; v == m_final[u]; v = m_thread[v]) {
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m_depth[v] -= d;
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}
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}
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m_thread[m_final[alpha2]] = src_out;
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}
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TRACE("network_flow", tout << pp_vector("Predecessors", m_pred, true) << pp_vector("Threads", m_thread)
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<< pp_vector("Reverse Threads", m_rev_thread) << pp_vector("Last Successors", m_final) << pp_vector("Depths", m_depth););
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}
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template<typename Ext>
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std::string network_flow<Ext>::pp_vector(std::string const & label, svector<int> v, bool has_header) {
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std::ostringstream oss;
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if (has_header) {
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oss << "Index ";
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for (unsigned i = 0; i < v.size(); ++i) {
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oss << i << " ";
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}
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oss << std::endl;
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}
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oss << label << " ";
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for (unsigned i = 0; i < v.size(); ++i) {
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oss << v[i] << " ";
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}
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oss << std::endl;
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return oss.str();
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}
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// Get the optimal solution
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template<typename Ext>
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typename network_flow<Ext>::numeral network_flow<Ext>::get_optimal_solution(vector<numeral> & result, bool is_dual) {
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m_objective_value = numeral::zero();
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for (unsigned i = 0; i < m_flows.size(); ++i) {
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m_objective_value += m_costs[i] * m_flows[i];
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std::string network_flow<Ext>::pp_vector(std::string const & label, vector<numeral> v, bool has_header) {
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std::ostringstream oss;
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if (has_header) {
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oss << "Index ";
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for (unsigned i = 0; i < v.size(); ++i) {
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oss << i << " ";
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}
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oss << std::endl;
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}
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result.reset();
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if (is_dual) {
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result.append(m_potentials);
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oss << label << " ";
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for (unsigned i = 0; i < v.size(); ++i) {
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oss << v[i] << " ";
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}
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else {
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result.append(m_flows);
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}
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return m_objective_value;
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oss << std::endl;
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return oss.str();
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}
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// Minimize cost flows
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@ -232,6 +345,24 @@ namespace smt {
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}
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return true;
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}
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// Get the optimal solution
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template<typename Ext>
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typename network_flow<Ext>::numeral network_flow<Ext>::get_optimal_solution(vector<numeral> & result, bool is_dual) {
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m_objective_value = numeral::zero();
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for (unsigned i = 0; i < m_flows.size(); ++i) {
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fin_numeral cost = m_graph.get_weight(i).get_rational();
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m_objective_value += cost * m_flows[i];
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}
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result.reset();
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if (is_dual) {
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result.append(m_potentials);
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}
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else {
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result.append(m_flows);
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}
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return m_objective_value;
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}
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}
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#endif
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@ -1008,34 +1008,25 @@ bool theory_diff_logic<Ext>::maximize(theory_var v) {
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verbose_stream() << "coefficient " << objective[i].second << " of theory_var " << objective[i].first << "\n";
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}
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verbose_stream() << m_objective_consts[v] << "\n";);
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NOT_IMPLEMENTED_YET();
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// Double the number of edges in the new graph
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// NSB review: what about disabled edges? They should not be added, right?
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// For efficiency we probably want to reuse m_graph and keep extra edges on the side or add them to
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// m_graph as well.
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dl_graph<GExt> g;
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vector<dl_edge<GExt> > const& es = m_graph.get_all_edges();
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for (unsigned i = 0; i < es.size(); ++i) {
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dl_edge<GExt> const & e = es[i];
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if (e.is_enabled()) {
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g.enable_edge(g.add_edge(e.get_source(), e.get_target(), e.get_weight(), e.get_explanation()));
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}
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}
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||||
|
||||
// Objective coefficients now become balances
|
||||
vector<fin_numeral> balances;
|
||||
vector<fin_numeral> balances(m_graph.get_num_nodes());
|
||||
balances.fill(fin_numeral::zero());
|
||||
for (unsigned i = 0; i < objective.size(); ++i) {
|
||||
fin_numeral balance(objective[i].second);
|
||||
balances.push_back(balance);
|
||||
balances[objective[i].first] = balance;
|
||||
}
|
||||
|
||||
network_flow<GExt> net_flow(g, balances);
|
||||
network_flow<GExt> net_flow(m_graph, balances);
|
||||
bool is_optimal = net_flow.min_cost();
|
||||
if (is_optimal) {
|
||||
vector<numeral> potentials;
|
||||
m_objective_value = net_flow.get_optimal_solution(potentials, true);
|
||||
std::cout << "Objective value of " << v << ": " << m_objective_value << std::endl;
|
||||
// TODO: return the model of the optimal solution from potential
|
||||
}
|
||||
else {
|
||||
std::cout << "Unbounded" << std::endl;
|
||||
}
|
||||
return is_optimal;
|
||||
}
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue