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https://github.com/Z3Prover/z3
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debugging network simplex
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
192ce11ca6
commit
5fc429c501
6 changed files with 75 additions and 102 deletions
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@ -28,7 +28,7 @@ namespace smt {
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template<typename Ext>
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bool network_flow<Ext>::first_eligible_pivot::choose_entering_edge() {
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TRACE("network_flow", tout << "choose_entering_edge...\n";);
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numeral cost = numeral::zero();
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int num_edges = m_graph.get_num_edges();
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for (int i = m_next_edge; i < m_next_edge + num_edges; ++i) {
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edge_id id = i % num_edges;
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@ -37,65 +37,51 @@ namespace smt {
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}
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node src = m_graph.get_source(id);
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node tgt = m_graph.get_target(id);
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numeral cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(id);
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cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(id);
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if (cost.is_pos()) {
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m_next_edge = m_enter_id = id;
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TRACE("network_flow",
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tout << "Found entering edge " << id << " between node ";
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tout << src << " and node " << tgt << " with reduced cost = " << cost << "...\n";);
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return true;
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}
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}
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TRACE("network_flow", tout << "Found no entering edge...\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>::best_eligible_pivot::choose_entering_edge() {
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TRACE("network_flow", tout << "choose_entering_edge...\n";);
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unsigned num_edges = m_graph.get_num_edges();
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numeral max = numeral::zero();
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numeral cost = numeral::zero();
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for (unsigned i = 0; i < num_edges; ++i) {
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node src = m_graph.get_source(i);
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node tgt = m_graph.get_target(i);
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if (!edge_in_tree(i)) {
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numeral cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(i);
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if (cost > max) {
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max = cost;
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numeral new_cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(i);
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if (new_cost > cost) {
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cost = new_cost;
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m_enter_id = i;
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}
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}
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}
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if (max.is_pos()) {
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TRACE("network_flow", {
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tout << "Found entering edge " << m_enter_id << " between node ";
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tout << m_graph.get_source(m_enter_id) << " and node " << m_graph.get_target(m_enter_id);
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tout << " with reduced cost = " << max << "...\n";
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});
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return true;
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}
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TRACE("network_flow", tout << "Found no entering edge...\n";);
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return false;
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return cost.is_pos();
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};
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template<typename Ext>
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bool network_flow<Ext>::candidate_list_pivot::choose_entering_edge() {
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numeral cost = numeral::zero();
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if (m_current_length == 0 || m_minor_step == MINOR_STEP_LIMIT) {
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// Build the candidate list
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unsigned num_edges = m_graph.get_num_edges();
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numeral max = numeral::zero();
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m_current_length = 0;
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for (unsigned i = m_next_edge; i < m_next_edge + num_edges; ++i) {
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edge_id id = (i >= num_edges) ? i - num_edges : i;
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node src = m_graph.get_source(id);
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node tgt = m_graph.get_target(id);
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if (!edge_in_tree(id)) {
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numeral cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(id);
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if (cost.is_pos()) {
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numeral new_cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(id);
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if (new_cost.is_pos()) {
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m_candidates[m_current_length] = id;
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++m_current_length;
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if (cost > max) {
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max = cost;
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if (new_cost > cost) {
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cost = new_cost;
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m_enter_id = id;
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}
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}
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@ -104,48 +90,29 @@ namespace smt {
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}
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m_next_edge = m_enter_id;
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m_minor_step = 1;
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if (max.is_pos()) {
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TRACE("network_flow", {
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tout << "Found entering edge " << m_enter_id << " between node ";
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tout << m_graph.get_source(m_enter_id) << " and node " << m_graph.get_target(m_enter_id);
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tout << " with reduced cost = " << max << "...\n";
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});
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return true;
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}
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TRACE("network_flow", tout << "Found no entering edge...\n";);
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return false;
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return cost.is_pos();
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}
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++m_minor_step;
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numeral max = numeral::zero();
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for (unsigned i = 0; i < m_current_length; ++i) {
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edge_id id = m_candidates[i];
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node src = m_graph.get_source(id);
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node tgt = m_graph.get_target(id);
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if (!edge_in_tree(id)) {
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numeral cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(id);
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if (cost > max) {
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max = cost;
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numeral new_cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(id);
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if (new_cost > cost) {
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cost = new_cost;
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m_enter_id = id;
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}
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// Remove stale candidates
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if (!cost.is_pos()) {
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if (!new_cost.is_pos()) {
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--m_current_length;
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m_candidates[i] = m_candidates[m_current_length];
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--i;
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}
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}
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}
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if (max.is_pos()) {
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TRACE("network_flow", {
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tout << "Found entering edge " << m_enter_id << " between node ";
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tout << m_graph.get_source(m_enter_id) << " and node " << m_graph.get_target(m_enter_id);
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tout << " with reduced cost = " << max << "...\n";
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});
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return true;
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}
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TRACE("network_flow", tout << "Found no entering edge...\n";);
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return false;
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return cost.is_pos();
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};
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template<typename Ext>
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@ -167,7 +134,7 @@ namespace smt {
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tout << "Difference logic optimization:" << std::endl;
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display_dual(tout);
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tout << "Minimum cost flow:" << std::endl;
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display(tout);
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display_primal(tout);
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};);
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m_step = 0;
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@ -219,7 +186,8 @@ namespace smt {
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tout << pp_vector("Flows", m_flows);
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tout << "Cost: " << get_cost() << "\n";
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tout << "Spanning tree:\n";
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display_spanning_tree(tout););
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display_spanning_tree(tout);
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display_primal(tout););
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SASSERT(check_well_formed());
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}
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@ -252,7 +220,6 @@ namespace smt {
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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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m_flows[m_enter_id] += *m_delta;
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node src = m_graph.get_source(m_enter_id);
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node tgt = m_graph.get_target(m_enter_id);
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@ -269,7 +236,6 @@ namespace smt {
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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 src = m_graph.get_source(m_enter_id);
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node tgt = m_graph.get_target(m_enter_id);
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m_delta.set_invalid();
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@ -286,14 +252,7 @@ namespace smt {
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}
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}
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m_leave_id = leave_id;
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TRACE("network_flow",
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tout << "Leaving edge " << m_leave_id;
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tout << " between node " << m_graph.get_source(m_leave_id);
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tout << " and node " << m_graph.get_target(m_leave_id) ;
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if (m_delta) tout << " with delta = " << *m_delta;
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tout << "\n";);
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return m_delta;
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}
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@ -329,6 +288,19 @@ namespace smt {
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while (choose_entering_edge(pr)) {
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bool bounded = choose_leaving_edge();
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if (!bounded) return UNBOUNDED;
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//TRACE("network_flow",
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{
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vector<edge>const& es = m_graph.get_all_edges();
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edge const& e_in = es[m_enter_id];
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edge const& e_out = es[m_leave_id];
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node src_in = e_in.get_source(), tgt_in = e_in.get_target();
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node src_out = e_out.get_source(), tgt_out = e_out.get_target();
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numeral c1 = m_potentials[src_in] - m_potentials[tgt_in] - m_graph.get_weight(m_enter_id);
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numeral c2 = m_potentials[src_out] - m_potentials[tgt_out] - m_graph.get_weight(m_leave_id);
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tout << "new base: y_" << src_in << "_" << tgt_in << " cost: " << c1 << " delta: " << *m_delta << "\n";
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tout << "old base: y_" << src_out << "_" << tgt_out << " cost: " << c2 << "\n";
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}
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// );
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update_flows();
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if (m_enter_id != m_leave_id) {
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SASSERT(edge_in_tree(m_leave_id));
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@ -340,10 +312,18 @@ namespace smt {
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TRACE("network_flow",
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tout << "Spanning tree:\n";
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display_spanning_tree(tout);
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tout << "Cost: " << get_cost() << "\n";);
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tout << "Cost: " << get_cost() << "\n";
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display_primal(tout);
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);
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SASSERT(check_well_formed());
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}
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}
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TRACE("network_flow",
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tout << "Spanning tree:\n";
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display_spanning_tree(tout);
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tout << "Cost: " << get_cost() << "\n";
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display_primal(tout);
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);
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if (is_infeasible()) return INFEASIBLE;
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TRACE("network_flow", tout << "Found optimal solution.\n";);
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SASSERT(check_optimal());
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@ -352,14 +332,13 @@ namespace smt {
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template<typename Ext>
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bool network_flow<Ext>::is_infeasible() {
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#if 0
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// Flows of artificial arcs should be zero
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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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SASSERT(m_flows.size() == num_edges);
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for (unsigned i = 1; i < num_nodes; ++i) {
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if (m_flows[num_edges - i].is_pos()) return true;
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}
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#endif
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return false;
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}
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@ -445,7 +424,7 @@ namespace smt {
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// display methods
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template<typename Ext>
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void network_flow<Ext>::display(std::ofstream & os) {
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void network_flow<Ext>::display_primal(std::ofstream & os) {
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vector<edge> const & es = m_graph.get_all_edges();
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for (unsigned i = 0; i < m_graph.get_num_edges(); ++i) {
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edge const & e = es[i];
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@ -486,6 +465,12 @@ namespace smt {
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};
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os << "))" << std::endl;
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os << "(optimize)" << std::endl;
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if (!m_flows.empty()) {
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for (unsigned i = 0; i < m_graph.get_num_edges(); ++i) {
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edge const & e = es[i];
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os << "; y_" << e.get_source() << "_" << e.get_target() << " = " << m_flows[i] << "\n";
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}
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}
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}
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