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https://github.com/Z3Prover/z3
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collect the explanation correctly
This commit is contained in:
Lev Nachmanson
Lev Nachmanson
parent
bc0fdfe158
commit
174185582a
2 changed files with 88 additions and 40 deletions
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@ -23,10 +23,13 @@
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-- lia: point to int_solver.
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-- m_entries: it keeps all "entry" objects.
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-- m_e_matrix: i-th row of this matrix keeps the term corresponding to
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m_entries[i]. The actual term is the sum of the matrix row and the constant
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m_c of the entry. The column j of the matrix corresponds to j column of
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lar_solver if j < lra.column_count(). Otherwise, j is a fresh column. It has
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to change in the interactive version. Implementation remarks:
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m_entries[i]. The actual term corresponding to m_entry[i] is the sum of the
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matrix i-th row and the constant m_entry[].m_c.
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The mapping between the columns of lar_solver and m_e_matrix is controlled by m_var_register.
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local_to_lar_solver(lar_solver_to_local(j)) == j. If local_to_lar_solver(j) == -1
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then j is a fresh variable, that is such that got introduced when normalizing a term like 3x-6y + 5z +11 = 0,
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when no variable has a coefficient +-1.
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-- get_term_from_entry(unsigned i) return a term corresponding i-th entry.
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If t = get_term_from_entry(i) then we have equality t = 0. Initially
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get_term_from_entry(i) is set to initt(j) = lra.get_term(j) - j, for some
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@ -246,6 +249,7 @@ namespace lp {
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bool m_left;
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bool m_fully_explored = false;
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void flip() {
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SASSERT(m_fully_explored == false);
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m_left = !m_left;
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m_fully_explored = true;
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}
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@ -415,6 +419,8 @@ namespace lp {
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// A conflict is reported when the gcd of the monomial coefficients does not divide the free coefficent.
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// If there is no conflict the entry is divided, normalized, by gcd.
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// The function returns true if and only if there is no conflict. In the case of a conflict a branch
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// can be returned as well.
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bool normalize_e_by_gcd(unsigned ei) {
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entry& e = m_entries[ei];
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TRACE("dioph_eq", print_entry(ei, tout) << std::endl;);
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@ -437,7 +443,7 @@ namespace lp {
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return true;
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}
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// c_g is not integral
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if (lra.settings().stats().m_dio_conflicts %
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if (lra.stats().m_dio_calls %
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lra.settings().dio_cut_from_proof_period() ==
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0 &&
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!has_fresh_var(ei))
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@ -563,7 +569,7 @@ namespace lp {
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subs_front_in_indexed_vector(q);
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}
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lia_move tighten_with_S() {
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lia_move tighten_terms_with_S() {
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for (unsigned j = 0; j < lra.column_count(); j++) {
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if (!lra.column_has_term(j) || lra.column_is_free(j) ||
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is_fixed(j) || !lia.column_is_int(j))
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@ -792,26 +798,35 @@ namespace lp {
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return dep;
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}
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lia_move iterate() {
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lia_move process_f() {
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while (m_f.size()) {
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if (!normalize_by_gcd()) {
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lra.settings().stats().m_dio_conflicts++;
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if (m_report_branch) {
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lra.stats().m_dio_cut_from_proofs++;
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m_report_branch = false;
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return lia_move::branch;
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} else {
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lra.stats().m_dio_normalize_conflicts++;
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}
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return lia_move::conflict;
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}
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rewrite_eqs();
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if (m_conflict_index != UINT_MAX) {
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lra.settings().stats().m_dio_conflicts++;
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lra.stats().m_dio_rewrite_conflicts++;
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return lia_move::conflict;
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}
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}
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return lia_move::undef;
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}
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lia_move process_f_and_tighten_terms() {
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lia_move ret = process_f();
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if (ret != lia_move::undef)
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return ret;
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TRACE("dioph_eq", print_S(tout););
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lia_move ret = tighten_with_S();
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ret = tighten_terms_with_S();
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if (ret == lia_move::conflict) {
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lra.settings().stats().m_dio_conflicts++;
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lra.stats().m_dio_tighten_conflicts++;
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return lia_move::conflict;
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}
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return lia_move::undef;
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@ -835,16 +850,13 @@ namespace lp {
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}
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// returns true if the left and the right branches were explored
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bool undo_last_branch() {
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if (m_branch_stack.back().m_fully_explored) {
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TRACE("dio_br", tout << "pop fully explored, m_branch_stack.size():" << m_branch_stack.size() << std::endl;);
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void undo_explored_branches() {
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TRACE("dio_br", tout << "m_branch_stack.size():" << m_branch_stack.size() << std::endl;);
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while (m_branch_stack.size() && m_branch_stack.back().m_fully_explored) {
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m_branch_stack.pop_back();
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return true;
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lra_pop();
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}
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// exploring the other side of the branch
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TRACE("dio_br", tout << "flipped branch" << std::endl;);
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m_branch_stack.back().flip();
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return false;
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TRACE("dio_br", tout << "after pop:m_branch_stack.size():" << m_branch_stack.size() << std::endl;);
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}
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lia_move check_fixing(unsigned j) const {
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@ -903,6 +915,7 @@ namespace lp {
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if (br.m_j == UINT_MAX)
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return false;
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m_branch_stack.push_back(br);
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lra.stats().m_dio_branching_depth = std::max(lra.stats().m_dio_branching_depth, (unsigned)m_branch_stack.size());
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return true;
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}
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@ -912,10 +925,10 @@ namespace lp {
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} else {
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lra.add_var_bound(b->m_j, lconstraint_kind::GE, b->m_rs + mpq(1));
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}
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if (lra.column_is_fixed(b->m_j)) {
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if (fix_var(lar_solver_to_local(b->m_j)) == lia_move::conflict)
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return lia_move::conflict;
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}
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// if (lra.column_is_fixed(b->m_j)) {
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// if (fix_var(lar_solver_to_local(b->m_j)) == lia_move::conflict)
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// return lia_move::conflict;
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// }
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return lia_move::undef;
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}
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@ -927,20 +940,32 @@ namespace lp {
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}
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void lra_pop() {
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m_lra_level--;
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SASSERT(m_lra_level != UINT_MAX);
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lra.pop();
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lra.find_feasible_solution();
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SASSERT(lra.get_status() == lp_status::CANCELLED || lra.is_feasible());
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}
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lia_move process_undef() {
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void transfer_explanations_from_closed_branches() {
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m_infeas_explanation.clear();
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for (auto ci : m_explanation_of_branches) {
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if (this->lra.constraints().valid_index(ci))
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m_infeas_explanation.push_back(ci);
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}
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}
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lia_move branching_on_undef() {
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m_explanation_of_branches.clear();
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branch* b;
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bool need_create_branch = true;
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m_number_of_iterations = 0;
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while (++m_number_of_iterations < m_max_number_of_iterations) {
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lra.stats().m_dio_branch_iterations++;
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if (need_create_branch) {
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if (!push_branch()) {
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undo_branching();
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lra.stats().m_dio_branching_sats++;
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return lia_move::sat;
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}
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need_create_branch = false;
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@ -950,13 +975,16 @@ namespace lp {
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if (add_var_bound_for_branch(b) == lia_move::conflict) {
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collect_evidence();
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if (m_branch_stack.size() == 0)
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undo_explored_branches();
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if (m_branch_stack.size() == 0) {
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lra.stats().m_dio_branching_infeasibles++;
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transfer_explanations_from_closed_branches();
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return lia_move::conflict;
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}
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TRACE("dio_br", tout << lp_status_to_string(lra.get_status()) << std::endl;
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tout << "explanation:\n"; lra.print_expl(tout, m_infeas_explanation););
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if (undo_last_branch())
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need_create_branch = true;
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lra_pop();
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need_create_branch = false;
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m_branch_stack.back().flip();
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continue;
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}
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auto st = lra.find_feasible_solution();
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@ -966,6 +994,7 @@ namespace lp {
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TRACE("dio_br", tout << "n_of_ii:" << n_of_ii << "\n";);
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if (n_of_ii == 0) {
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undo_branching();
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lra.stats().m_dio_branching_sats++;
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return lia_move::sat;
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}
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// got to create a new branch
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@ -974,13 +1003,19 @@ namespace lp {
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} else {
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if (st == lp_status::CANCELLED) return lia_move::undef;
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collect_evidence();
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if (m_branch_stack.size() == 0)
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return lia_move::conflict;
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undo_explored_branches();
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if (m_branch_stack.size() == 0) {
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lra.stats().m_dio_branching_infeasibles++;
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transfer_explanations_from_closed_branches();
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enable_trace("dioph_eq");
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return lia_move::conflict;
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}
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TRACE("dio_br", tout << lp_status_to_string(lra.get_status()) << std::endl;
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tout << "explanation:\n"; lra.print_expl(tout, m_infeas_explanation););
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if (undo_last_branch())
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need_create_branch = true;
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need_create_branch = false;
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lra_pop();
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m_branch_stack.back().flip();
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}
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}
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undo_branching();
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@ -1049,20 +1084,20 @@ namespace lp {
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br.m_left = (lra.settings().random_next() % 2 == 0);
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br.m_rs = floor(lra.get_column_value(bj).x);
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TRACE("dio_br", tout << " br.m_j:" << br.m_j << ","
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TRACE("dio_br", tout << "score:" << score << "; br.m_j:" << br.m_j << ","
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<< (br.m_left ? "left" : "right") << ", br.m_rs:" << br.m_rs << std::endl;);
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return br;
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}
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public:
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lia_move check() {
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lra.settings().stats().m_dio_calls++;
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lra.stats().m_dio_calls++;
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init();
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lia_move ret = iterate();
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lia_move ret = process_f_and_tighten_terms();
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if (ret == lia_move::branch || ret == lia_move::conflict)
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return ret;
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SASSERT(ret == lia_move::undef);
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ret = process_undef();
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ret = branching_on_undef();
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if (ret == lia_move::sat || ret == lia_move::conflict)
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return ret;
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SASSERT(ret == lia_move::undef);
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@ -1382,8 +1417,6 @@ namespace lp {
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public:
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void explain(explanation& ex) {
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if (m_conflict_index == UINT_MAX) {
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SASSERT(!(lra.get_status() == lp_status::FEASIBLE ||
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lra.get_status() == lp_status::OPTIMAL));
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for (auto ci : m_infeas_explanation) {
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ex.push_back(ci.ci());
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}
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@ -128,8 +128,15 @@ struct statistics {
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unsigned m_grobner_conflicts = 0;
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unsigned m_offset_eqs = 0;
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unsigned m_fixed_eqs = 0;
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unsigned m_dio_conflicts = 0;
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unsigned m_dio_calls = 0;
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unsigned m_dio_normalize_conflicts = 0;
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unsigned m_dio_tighten_conflicts = 0;
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unsigned m_dio_branch_iterations= 0;
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unsigned m_dio_branching_depth = 0;
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unsigned m_dio_cut_from_proofs = 0;
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unsigned m_dio_branching_infeasibles = 0;
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unsigned m_dio_rewrite_conflicts = 0;
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unsigned m_dio_branching_sats = 0;
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::statistics m_st = {};
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void reset() {
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@ -163,7 +170,15 @@ struct statistics {
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st.update("arith-nra-calls", m_nra_calls);
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st.update("arith-bounds-improvements", m_nla_bounds_improvements);
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st.update("arith-dio-calls", m_dio_calls);
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st.update("arith-dio-conflicts", m_dio_conflicts);
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st.update("arith-dio-normalize-conflicts", m_dio_normalize_conflicts);
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st.update("arith-dio-tighten-conflicts", m_dio_tighten_conflicts);
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st.update("arith-dio-branch-iterations", m_dio_branch_iterations);
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st.update("arith-dio-branch-depths", m_dio_branching_depth);
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st.update("arith-dio-cut-from-proofs", m_dio_cut_from_proofs);
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st.update("arith-dio-branching-infeasibles", m_dio_branching_infeasibles);
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st.update("arith-dio-rewrite-conflicts", m_dio_rewrite_conflicts);
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st.update("arith-dio-branching-sats", m_dio_branching_sats);
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st.update("arith-dio-branching-depth", m_dio_branching_depth);
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st.copy(m_st);
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}
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};
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