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Polysat: conflict explanation prototype (#5353)
* display constraint's extra info in one place * Add stub for conflict explainer * Add helper functions to check whether constraint is active at base level * Add helper class tmp_assign * Add clause_builder; it skips unnecessary literals during clause creation * some fixes * Use clause_builder for forbidden intervals * remove old comments * fixes/comments in solver * print redundant clauses * First pass at conflict_explainer * remove unused model class * Choose value for k * also print min/max k
This commit is contained in:
Jakob Rath
GitHub
parent
1fe7dc40fe
commit
3e1cfcd538
11 changed files with 449 additions and 60 deletions
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@ -17,6 +17,7 @@ Author:
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--*/
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#include "math/polysat/solver.h"
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#include "math/polysat/explain.h"
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#include "math/polysat/log.h"
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#include "math/polysat/forbidden_intervals.h"
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@ -550,6 +551,13 @@ namespace polysat {
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m_bvars.reset_marks();
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set_marks(*lemma.get());
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}
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else {
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// lemma = resolve(conflict_var);
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conflict_explainer cx(*this, m_conflict);
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lemma = cx.resolve(conflict_var, {});
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LOG("resolved: " << show_deref(lemma));
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// std::abort();
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}
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}
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for (unsigned i = m_search.size(); i-- > 0; ) {
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@ -615,6 +623,8 @@ namespace polysat {
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SASSERT(m_bvars.is_propagation(var));
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clause_ref new_lemma = resolve_bool(lit);
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SASSERT(new_lemma);
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LOG("new_lemma: " << show_deref(new_lemma));
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LOG("new_lemma is always false: " << new_lemma->is_always_false(*this));
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if (new_lemma->is_always_false(*this)) {
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// learn_lemma(v, new_lemma);
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m_conflict.reset();
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@ -622,10 +632,11 @@ namespace polysat {
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report_unsat();
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return;
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}
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if (!new_lemma->is_currently_false(*this)) {
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backtrack(i, lemma);
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return;
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}
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LOG("new_lemma is currently false: " << new_lemma->is_currently_false(*this));
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// if (!new_lemma->is_currently_false(*this)) {
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// backtrack(i, lemma);
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// return;
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// }
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lemma = std::move(new_lemma);
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reset_marks();
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m_bvars.reset_marks();
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@ -642,12 +653,26 @@ namespace polysat {
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return nullptr;
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if (m_conflict.clauses().size() != 1)
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return nullptr;
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LOG_H3("resolve_bool");
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clause* lemma = m_conflict.clauses()[0];
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SASSERT(lemma);
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SASSERT(m_bvars.is_propagation(lit.var()));
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clause* other = m_bvars.reason(lit.var());
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SASSERT(other);
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LOG("lemma: " << show_deref(lemma));
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LOG("other: " << show_deref(other));
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VERIFY(lemma->resolve(lit.var(), *other));
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LOG("resolved: " << show_deref(lemma));
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// unassign constraints whose current value does not agree with their occurrence in the lemma
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for (sat::literal lit : *lemma) {
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constraint *c = m_constraints.lookup(lit.var());
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if (!c->is_undef() && c ->blit() != lit) {
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LOG("unassigning: " << show_deref(c));
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c->unassign();
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}
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}
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return lemma; // currently modified in-place
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}
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@ -764,17 +789,14 @@ namespace polysat {
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IF_LOGGING(log_viable());
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LOG("Boolean assignment: " << m_bvars);
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// To make a guess, we need to find an unassigned literal that is not false in the current model.
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auto is_suitable = [this](sat::literal lit) -> bool {
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if (m_bvars.value(lit) == l_false) // already assigned => cannot decide on this (comes from either lemma LHS or previously decided literals that are now changed to propagation)
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return false;
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SASSERT(m_bvars.value(lit) != l_true); // cannot happen in a valid lemma
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constraint* c = m_constraints.lookup(lit.var());
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c->assign(!lit.sign());
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bool result = true;
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if (c->is_currently_false(*this))
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result = false;
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c->unassign();
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return result;
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tmp_assign _t(c, lit);
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return !c->is_currently_false(*this);
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};
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// constraint *choice = nullptr;
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@ -782,19 +804,15 @@ namespace polysat {
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unsigned num_choices = 0; // TODO: should probably cache this?
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for (sat::literal lit : lemma) {
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IF_LOGGING({
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auto value = m_bvars.value(lit);
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auto c = m_constraints.lookup(lit.var());
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bool is_false;
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if (value == l_undef) {
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c->assign(!lit.sign());
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is_false = c->is_currently_false(*this);
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c->unassign();
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}
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else
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is_false = c->is_currently_false(*this);
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LOG_V("Checking: lit=" << lit << ", value=" << value << ", constraint=" << show_deref(c) << ", currently_false=" << is_false);
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});
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// IF_LOGGING({
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// auto value = m_bvars.value(lit);
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// auto c = m_constraints.lookup(lit.var());
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// bool is_false;
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// LOG_V("Checking: lit=" << lit << ", value=" << value << ", constraint=" << show_deref(c));
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// tmp_assign _t(c, lit);
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// is_false = c->is_currently_false(*this);
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// LOG_V("Checking: lit=" << lit << ", value=" << value << ", constraint=" << show_deref(c) << ", currently_false=" << is_false);
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// });
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if (is_suitable(lit)) {
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num_choices++;
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if (choice == sat::null_literal)
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@ -886,7 +904,9 @@ namespace polysat {
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// - Guess x = 0.
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// - We have a conflict but we don't know. It will be discovered when y and z are assigned,
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// and then may lead to an assertion failure through this call to narrow.
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c->narrow(*this);
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// TODO: what to do with "unassigned" constraints at this point? (we probably should have resolved those away, even in the 'backtrack' case.)
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if (!c->is_undef()) // TODO: this check to be removed once this is fixed properly.
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c->narrow(*this);
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if (is_conflict()) {
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LOG_H1("Conflict during revert_decision/narrow!");
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return;
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@ -1048,10 +1068,19 @@ namespace polysat {
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* Return residue of superposing p and q with respect to v.
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*/
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clause_ref solver::resolve(pvar v) {
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LOG_H3("Resolve v" << v);
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SASSERT(!m_cjust[v].empty());
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SASSERT(m_justification[v].is_propagation());
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LOG("resolve pvar " << v);
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if (m_cjust[v].size() != 1)
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LOG("Conflict: " << m_conflict);
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LOG("cjust[v" << v << "]: " << m_cjust[v]);
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conflict_explainer cx(*this, m_conflict);
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clause_ref res = cx.resolve(v, m_cjust[v]);
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LOG("resolved: " << show_deref(res));
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// std::abort();
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return res;
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/*
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if (m_cjust[v].size() != 1)
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return nullptr;
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constraint* d = m_cjust[v].back();
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constraint_ref res = d->resolve(*this, v);
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@ -1062,6 +1091,7 @@ namespace polysat {
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}
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else
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return nullptr;
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*/
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}
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/**
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@ -1085,7 +1115,10 @@ namespace polysat {
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if (!lemma)
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return;
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LOG("Lemma: " << show_deref(lemma));
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SASSERT(lemma->size() > 1);
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// SASSERT(lemma->size() > 1);
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if (lemma->size() < 2) {
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LOG_H1("TODO: this should be treated as unit constraint and asserted at the base level!");
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}
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clause* cl = m_constraints.insert(lemma);
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m_redundant_clauses.push_back(cl);
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}
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@ -1132,7 +1165,18 @@ namespace polysat {
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unsigned solver::base_level() const {
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return m_base_levels.empty() ? 0 : m_base_levels.back();
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}
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bool solver::active_at_base_level(sat::bool_var bvar) const {
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return m_bvars.is_assigned(bvar) && m_bvars.level(bvar) <= base_level();
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}
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bool solver::try_eval(pdd const& p, rational& out_value) const {
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pdd r = p.subst_val(assignment());
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if (r.is_val())
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out_value = r.val();
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return r.is_val();
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}
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std::ostream& solver::display(std::ostream& out) const {
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for (auto p : assignment()) {
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auto v = p.first;
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@ -1146,6 +1190,14 @@ namespace polysat {
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out << "Redundant:\n";
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for (auto* c : m_redundant)
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out << "\t" << *c << "\n";
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out << "Redundant clauses:\n";
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for (auto* cl : m_redundant_clauses) {
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out << "\t" << *cl << "\n";
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for (auto lit : *cl) {
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auto c = m_constraints.lookup(lit.var());
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out << "\t\t" << lit.var() << ": " << *c << "\n";
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}
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}
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return out;
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}
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