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https://github.com/Z3Prover/z3
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WIP revamp conflict state
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner
parent
60248d0981
commit
b488a1fadd
6 changed files with 50 additions and 55 deletions
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@ -50,8 +50,7 @@ namespace polysat {
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if (!m_vars.empty())
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out << " vars";
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for (auto v : m_vars)
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if (is_pmarked(v))
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out << " v" << v;
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out << " v" << v;
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return out;
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}
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@ -83,7 +82,7 @@ namespace polysat {
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else {
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SASSERT(c.is_currently_false(s));
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// TBD: fails with test_subst SASSERT(c.bvalue(s) == l_true);
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c->set_var_dependent();
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insert_vars(c);
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insert(c);
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}
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SASSERT(!empty());
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@ -140,6 +139,13 @@ namespace polysat {
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m_constraints.push_back(c);
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}
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void conflict::insert_vars(signed_constraint c) {
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for (pvar v : c->vars())
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if (s.is_assigned(v))
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m_vars.insert(v);
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}
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/**
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* Premises can either be justified by a Clause or by a value assignment.
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@ -210,7 +216,7 @@ namespace polysat {
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SASSERT(std::count(cl.begin(), cl.end(), ~lit) == 0);
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remove_literal(lit);
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unset_bmark(s.lit2cnstr(lit));
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unset_mark(s.lit2cnstr(lit));
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for (sat::literal lit2 : cl)
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if (lit2 != lit)
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insert(s.lit2cnstr(~lit2));
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@ -229,12 +235,7 @@ namespace polysat {
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remove_literal(lit);
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signed_constraint c = s.lit2cnstr(lit);
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unset_mark(c);
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for (pvar v : c->vars()) {
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if (s.is_assigned(v) && s.get_level(v) <= lvl) {
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m_vars.insert(v);
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inc_pref(v);
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}
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}
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insert_vars(c);
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}
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/**
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@ -268,8 +269,6 @@ namespace polysat {
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lemma.push(~c);
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for (unsigned v : m_vars) {
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if (!is_pmarked(v))
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continue;
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auto eq = s.eq(s.var(v), s.get_value(v));
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cm().ensure_bvar(eq.get());
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if (eq.bvalue(s) == l_undef)
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@ -406,19 +405,12 @@ namespace polysat {
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c->set_mark();
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if (c->has_bvar())
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set_bmark(c->bvar());
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if (c->is_var_dependent()) {
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for (auto v : c->vars()) {
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if (s.is_assigned(v))
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m_vars.insert(v);
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inc_pref(v);
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}
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}
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}
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/**
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* unset marking on the constraint, but keep variable dependencies.
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*/
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void conflict::unset_bmark(signed_constraint c) {
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void conflict::unset_mark(signed_constraint c) {
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if (!c->is_marked())
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return;
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c->unset_mark();
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@ -426,32 +418,6 @@ namespace polysat {
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unset_bmark(c->bvar());
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}
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void conflict::unset_mark(signed_constraint c) {
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if (!c->is_marked())
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return;
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unset_bmark(c);
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if (!c->is_var_dependent())
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return;
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c->unset_var_dependent();
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for (auto v : c->vars())
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dec_pref(v);
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}
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void conflict::inc_pref(pvar v) {
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if (v >= m_pvar2count.size())
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m_pvar2count.resize(v + 1);
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m_pvar2count[v]++;
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}
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void conflict::dec_pref(pvar v) {
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SASSERT(m_pvar2count[v] > 0);
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m_pvar2count[v]--;
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}
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bool conflict::is_pmarked(pvar v) const {
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return m_pvar2count.get(v, 0) > 0;
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}
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void conflict::set_bmark(sat::bool_var b) {
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if (b >= m_bvar2mark.size())
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m_bvar2mark.resize(b + 1);
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@ -10,6 +10,37 @@ Author:
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Nikolaj Bjorner (nbjorner) 2021-03-19
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Jakob Rath 2021-04-6
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Notes:
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A conflict state is of the form <Vars, Constraints>
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Where Vars are shorthand for the constraints v = value(v) for v in Vars and value(v) is the assignent.
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The conflict state is unsatisfiable under background clauses F.
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Dually, the negation is a consequence of F.
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Conflict resolution resolves an assignment in the search stack against the conflict state.
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Assignments are of the form:
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lit <- D => lit - lit is propagated by the clause D => lit
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lit <- ? - lit is a decision literal.
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lit <- asserted - lit is asserted
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lit <- Vars - lit is propagated from variable evaluation.
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v = value <- Cs - v is assigned value by constraints Cs
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v = value <- ? - v is a decision literal.
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- All literals should be assigned in the stack prior to their use.
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lit <- D => lit, < Vars, { lit } u Cs > ===> < Vars, Cs u D >
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lit <- ?, < Vars, { lit } u Cs > ===> ~lit <- (Cs & Vars = value(Vars) => ~lit)
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lit <- asserted, < Vars, { lit } u Cs > ===> accumulate lit for a core
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lit <- Vars', < Vars, { lit } u Cs > ===> ~lit <- (Cs & Vars = value(Vars) => ~lit)
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v = value <- Cs, < Vars u { v }, Cs > ===>
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--*/
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#pragma once
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#include "math/polysat/constraint.h"
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@ -77,7 +108,7 @@ namespace polysat {
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void reset();
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bool is_pmarked(pvar v) const;
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bool contains_pvar(pvar v) const { return m_vars.contains(v); }
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bool is_bmarked(sat::bool_var b) const;
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/** conflict because the constraint c is false under current variable assignment */
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@ -88,6 +119,7 @@ namespace polysat {
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void set(clause const& cl);
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void insert(signed_constraint c);
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void insert_vars(signed_constraint c);
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void insert(signed_constraint c, vector<signed_constraint> const& premises);
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void remove(signed_constraint c);
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void replace(signed_constraint c_old, signed_constraint c_new, vector<signed_constraint> const& c_new_premises);
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@ -146,7 +146,6 @@ namespace polysat {
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unsigned_vector m_vars;
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lbool m_external_sign = l_undef;
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bool m_is_marked = false;
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bool m_is_var_dependent = false;
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bool m_is_active = false;
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/** The boolean variable associated to this constraint, if any.
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* If this is not null_bool_var, then the constraint corresponds to a literal on the assignment stack.
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@ -207,9 +206,6 @@ namespace polysat {
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void unset_mark() { m_is_marked = false; }
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bool is_marked() const { return m_is_marked; }
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void set_var_dependent() { m_is_var_dependent = true; }
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void unset_var_dependent() { m_is_var_dependent = false; }
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bool is_var_dependent() const { return m_is_var_dependent; }
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bool is_active() const { return m_is_active; }
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void set_active(bool f) { m_is_active = f; }
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@ -88,7 +88,7 @@ namespace polysat {
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for (auto d : m_new_constraints)
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core.insert(d);
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if (c.bvalue(s) != l_false)
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c->set_var_dependent();
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core.insert_vars(c);
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core.insert(~c);
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LOG("Core " << core);
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return true;
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@ -534,7 +534,7 @@ namespace polysat {
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if (item.is_assignment()) {
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// Resolve over variable assignment
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pvar v = item.var();
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if (!m_conflict.is_pmarked(v) && !m_conflict.is_bailout()) {
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if (!m_conflict.contains_pvar(v) && !m_conflict.is_bailout()) {
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m_search.pop_assignment();
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continue;
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}
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@ -557,9 +557,10 @@ namespace polysat {
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signed_constraint c = s.m_constraints.ult(lhs, rhs);
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core.insert(c);
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}
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for (auto sc : e->side_cond)
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for (auto sc : e->side_cond) {
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core.insert(sc);
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e->src->set_var_dependent();
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core.insert_vars(sc);
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}
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core.insert(e->src);
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e = n;
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}
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