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https://github.com/Z3Prover/z3
synced 2025-04-08 18:31:49 +00:00
Fix a few issues related to thread spanning tree
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761c95129b
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af8da013b5
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@ -244,7 +244,7 @@ namespace smt {
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};
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graph m_graph;
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thread_spanning_tree<Ext> m_tree;
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spanning_tree_base * m_tree;
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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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@ -27,8 +27,7 @@ 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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m_balances(balances),
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m_tree(m_graph) {
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m_balances(balances) {
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// Network flow graph has the edges in the reversed order compared to constraint graph
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// We only take enabled edges from the original graph
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for (unsigned i = 0; i < g.get_num_nodes(); ++i) {
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@ -42,6 +41,7 @@ namespace smt {
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}
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}
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m_step = 0;
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m_tree = alloc(thread_spanning_tree<Ext>, m_graph);
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}
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template<typename Ext>
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@ -82,7 +82,7 @@ namespace smt {
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tree.push_back(m_graph.add_edge(src, tgt, numeral::one(), explanation()));
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}
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m_tree.initialize(tree);
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m_tree->initialize(tree);
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TRACE("network_flow", {
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tout << pp_vector("Potentials", m_potentials, true) << pp_vector("Flows", m_flows);
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@ -96,14 +96,14 @@ namespace smt {
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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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numeral cost = m_potentials[src] - m_potentials[tgt] - m_graph.get_weight(m_enter_id);
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numeral change = m_tree.in_subtree_t2(tgt) ? cost : -cost;
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numeral change = m_tree->in_subtree_t2(tgt) ? cost : -cost;
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node start = m_graph.get_source(m_leave_id);
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if (!m_tree.in_subtree_t2(start)) {
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if (!m_tree->in_subtree_t2(start)) {
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start = m_graph.get_target(m_leave_id);;
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}
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TRACE("network_flow", tout << "update_potentials of T_" << start << " with change = " << change << "...\n";);
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svector<node> descendants;
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m_tree.get_descendants(start, descendants);
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m_tree->get_descendants(start, descendants);
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SASSERT(descendants.size() >= 1);
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for (unsigned i = 0; i < descendants.size(); ++i) {
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node u = descendants[i];
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@ -120,7 +120,7 @@ namespace smt {
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node tgt = m_graph.get_target(m_enter_id);
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svector<edge_id> path;
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svector<bool> against;
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m_tree.get_path(src, tgt, path, against);
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m_tree->get_path(src, tgt, path, against);
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SASSERT(path.size() >= 1);
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for (unsigned i = 0; i < path.size(); ++i) {
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edge_id e_id = path[i];
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@ -138,7 +138,7 @@ namespace smt {
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edge_id leave_id;
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svector<edge_id> path;
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svector<bool> against;
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m_tree.get_path(src, tgt, path, against);
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m_tree->get_path(src, tgt, path, against);
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SASSERT(path.size() >= 1);
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for (unsigned i = 0; i < path.size(); ++i) {
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edge_id e_id = path[i];
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@ -164,7 +164,7 @@ namespace smt {
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template<typename Ext>
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void network_flow<Ext>::update_spanning_tree() {
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m_tree.update(m_enter_id, m_leave_id);
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m_tree->update(m_enter_id, m_leave_id);
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}
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// FIXME: should declare pivot as a pivot_rule_impl and refactor
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@ -240,7 +240,7 @@ namespace smt {
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template<typename Ext>
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bool network_flow<Ext>::check_well_formed() {
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SASSERT(m_tree.check_well_formed());
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SASSERT(m_tree->check_well_formed());
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SASSERT(!m_delta || !(*m_delta).is_neg());
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// m_flows are zero on non-basic edges
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@ -49,7 +49,7 @@ namespace smt {
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void swap_order(node q, node v);
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node find_rev_thread(node n) const;
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void fix_depth(node start, node end);
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void fix_depth(node start, node after_end);
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node get_final(int start);
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bool is_preorder_traversal(node start, node end);
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node get_common_ancestor(node u, node v);
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@ -47,14 +47,14 @@ namespace smt {
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typedef int node;
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public:
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virtual void initialize(svector<edge_id> const & tree) {};
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virtual void get_descendants(node start, svector<node> & descendants) {};
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virtual void initialize(svector<edge_id> const & tree) = 0;
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virtual void get_descendants(node start, svector<node> & descendants) = 0;
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virtual void update(edge_id enter_id, edge_id leave_id) {};
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virtual void get_path(node start, node end, svector<edge_id> & path, svector<bool> & against) {};
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virtual bool in_subtree_t2(node child) {UNREACHABLE(); return false;};
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virtual void update(edge_id enter_id, edge_id leave_id) = 0;
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virtual void get_path(node start, node end, svector<edge_id> & path, svector<bool> & against) = 0;
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virtual bool in_subtree_t2(node child) = 0;
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virtual bool check_well_formed() {UNREACHABLE(); return false;};
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virtual bool check_well_formed() = 0;
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};
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}
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@ -162,11 +162,26 @@ namespace smt {
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tout << u << ", " << v << ") leaves\n";
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});
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// Old threads: alpha -> v -*-> f(v) -> beta | p -*-> f(p) -> gamma
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// New threads: alpha -> beta | p -*-> f(p) -> v -*-> f(v) -> gamma
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node f_p = get_final(p);
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node f_v = get_final(v);
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node alpha = find_rev_thread(v);
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node beta = m_thread[f_v];
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node gamma = m_thread[f_p];
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if (v != gamma) {
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m_thread[alpha] = beta;
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m_thread[f_p] = v;
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m_thread[f_v] = gamma;
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}
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node old_pred = m_pred[q];
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// Update stem nodes from q to v
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if (q != v) {
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for (node n = q; n != u; ) {
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SASSERT(old_pred != u || n == v); // the last processed node is v
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for (node n = q; n != v; ) {
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SASSERT(old_pred != u); // the last processed node is v
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SASSERT(-1 != m_pred[old_pred]);
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int next_old_pred = m_pred[old_pred];
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swap_order(n, old_pred);
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@ -175,34 +190,18 @@ namespace smt {
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old_pred = next_old_pred;
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}
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}
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// Old threads: alpha -> q -*-> f(q) -> beta | p -*-> f(p) -> gamma
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// New threads: alpha -> beta | p -*-> f(p) -> q -*-> f(q) -> gamma
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node f_p = get_final(p);
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node f_q = get_final(q);
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node alpha = find_rev_thread(q);
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node beta = m_thread[f_q];
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node gamma = m_thread[f_p];
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if (q != gamma) {
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m_thread[alpha] = beta;
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m_thread[f_p] = q;
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m_thread[f_q] = gamma;
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}
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m_pred[q] = p;
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m_tree[q] = enter_id;
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m_root_t2 = q;
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node after_final_q = (v == gamma) ? beta : gamma;
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fix_depth(q, after_final_q);
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SASSERT(!in_subtree_t2(p));
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SASSERT(in_subtree_t2(q));
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SASSERT(!in_subtree_t2(u));
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SASSERT(in_subtree_t2(v));
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// Update the depth.
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fix_depth(q, get_final(q));
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TRACE("network_flow", {
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tout << pp_vector("Predecessors", m_pred, true) << pp_vector("Threads", m_thread);
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@ -210,6 +209,53 @@ namespace smt {
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});
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}
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/**
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swap v and q in tree.
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- fixup m_thread
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- fixup m_pred
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Case 1: final(q) == final(v)
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-------
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Old thread: prev -> v -*-> alpha -> q -*-> final(q) -> next
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New thread: prev -> q -*-> final(q) -> v -*-> alpha -> next
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Case 2: final(q) != final(v)
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-------
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Old thread: prev -> v -*-> alpha -> q -*-> final(q) -> beta -*-> final(v) -> next
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New thread: prev -> q -*-> final(q) -> v -*-> alpha -> beta -*-> final(v) -> next
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*/
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template<typename Ext>
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void thread_spanning_tree<Ext>::swap_order(node q, node v) {
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SASSERT(q != v);
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SASSERT(m_pred[q] == v);
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SASSERT(is_preorder_traversal(v, get_final(v)));
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node prev = find_rev_thread(v);
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node f_q = get_final(q);
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node f_v = get_final(v);
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node next = m_thread[f_v];
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node alpha = find_rev_thread(q);
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if (f_q == f_v) {
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SASSERT(f_q != v && alpha != next);
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m_thread[f_q] = v;
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m_thread[alpha] = next;
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f_q = alpha;
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}
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else {
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node beta = m_thread[f_q];
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SASSERT(f_q != v && alpha != beta);
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m_thread[f_q] = v;
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m_thread[alpha] = beta;
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f_q = f_v;
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}
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SASSERT(prev != q);
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m_thread[prev] = q;
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m_pred[v] = q;
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// Notes: f_q has to be used since m_depth hasn't been updated yet.
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SASSERT(is_preorder_traversal(q, f_q));
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}
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/**
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\brief Check invariants of main data-structures.
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@ -311,53 +357,6 @@ namespace smt {
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roots[y] = x;
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}
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/**
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swap v and q in tree.
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- fixup m_thread
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- fixup m_pred
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Case 1: final(q) == final(v)
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-------
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Old thread: prev -> v -*-> alpha -> q -*-> final(q) -> next
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New thread: prev -> q -*-> final(q) -> v -*-> alpha -> next
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Case 2: final(q) != final(v)
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-------
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Old thread: prev -> v -*-> alpha -> q -*-> final(q) -> beta -*-> final(v) -> next
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New thread: prev -> q -*-> final(q) -> v -*-> alpha -> beta -*-> final(v) -> next
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*/
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template<typename Ext>
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void thread_spanning_tree<Ext>::swap_order(node q, node v) {
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SASSERT(q != v);
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SASSERT(m_pred[q] == v);
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SASSERT(is_preorder_traversal(v, get_final(v)));
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node prev = find_rev_thread(v);
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node f_q = get_final(q);
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node f_v = get_final(v);
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node next = m_thread[f_v];
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node alpha = find_rev_thread(q);
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if (f_q == f_v) {
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SASSERT(f_q != v && alpha != next);
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m_thread[f_q] = v;
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m_thread[alpha] = next;
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f_q = alpha;
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}
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else {
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node beta = m_thread[f_q];
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SASSERT(f_q != v && alpha != beta);
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m_thread[f_q] = v;
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m_thread[alpha] = beta;
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f_q = f_v;
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}
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SASSERT(prev != q);
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m_thread[prev] = q;
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m_pred[v] = q;
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// Notes: f_q has to be used since m_depth hasn't been updated yet.
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SASSERT(is_preorder_traversal(q, f_q));
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}
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/**
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\brief find node that points to 'n' in m_thread
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*/
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@ -372,12 +371,11 @@ namespace smt {
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}
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template<typename Ext>
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void thread_spanning_tree<Ext>::fix_depth(node start, node end) {
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SASSERT(m_pred[start] != -1);
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m_depth[start] = m_depth[m_pred[start]]+1;
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while (start != end) {
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start = m_thread[start];
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void thread_spanning_tree<Ext>::fix_depth(node start, node after_end) {
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while (start != after_end) {
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SASSERT(m_pred[start] != -1);
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m_depth[start] = m_depth[m_pred[start]]+1;
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start = m_thread[start];
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}
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}
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