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adding watches on Booleans

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2021-09-16 22:01:34 +01:00
parent c25fd71bf4
commit f01da40e49
7 changed files with 130 additions and 54 deletions
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125
src/math/polysat/solver.cpp
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@ -40,8 +40,9 @@ namespace polysat {
m_dm(m_value_manager, m_alloc),
m_linear_solver(*this),
m_conflict(*this),
m_free_vars(m_activity),
m_bvars(),
m_free_pvars(m_activity),
m_free_bvars(m_bvars.activity()),
m_constraints(m_bvars) {
}
@ -63,12 +64,11 @@ namespace polysat {
while (inc()) {
m_stats.m_num_iterations++;
LOG_H1("Next solving loop iteration (#" << m_stats.m_num_iterations << ")");
LOG("Free variables: " << m_free_vars);
LOG("Free variables: " << m_free_pvars);
LOG("Assignment: " << assignments_pp(*this));
if (!m_conflict.empty()) LOG("Conflict: " << m_conflict);
COND_LOG(is_conflict(), "Conflict: " << m_conflict);
IF_LOGGING(m_viable.log());
if (!is_conflict() && m_constraints.should_gc()) m_constraints.gc(*this);
if (pending_disjunctive_lemma()) { LOG_H2("UNDEF (handle lemma externally)"); return l_undef; }
else if (is_conflict() && at_base_level()) { LOG_H2("UNSAT"); return l_false; }
else if (is_conflict()) resolve_conflict();
@ -86,12 +86,12 @@ namespace polysat {
m_justification.push_back(justification::unassigned());
m_viable.push(sz);
m_cjust.push_back({});
m_watch.push_back({});
m_pwatch.push_back({});
m_activity.push_back(0);
m_vars.push_back(sz2pdd(sz).mk_var(v));
m_size.push_back(sz);
m_trail.push_back(trail_instr_t::add_var_i);
m_free_vars.mk_var_eh(v);
m_free_pvars.mk_var_eh(v);
return v;
}
@ -106,11 +106,11 @@ namespace polysat {
m_cjust.pop_back();
m_value.pop_back();
m_justification.pop_back();
m_watch.pop_back();
m_pwatch.pop_back();
m_activity.pop_back();
m_vars.pop_back();
m_size.pop_back();
m_free_vars.del_var_eh(v);
m_free_pvars.del_var_eh(v);
}
signed_constraint solver::eq(pdd const& p) {
@ -146,12 +146,11 @@ namespace polysat {
m_constraints.ensure_bvar(c.get());
clause* unit = m_constraints.store(clause::from_unit(m_level, c, mk_dep_ref(dep)));
c->set_unit_clause(unit);
if (dep != null_dependency)
if (!c->is_external()) {
m_constraints.register_external(c);
m_trail.push_back(trail_instr_t::ext_constraint_i);
m_ext_constraint_trail.push_back(c.get());
}
if (dep != null_dependency && !c->is_external()) {
m_constraints.register_external(c);
m_trail.push_back(trail_instr_t::ext_constraint_i);
m_ext_constraint_trail.push_back(c.get());
}
LOG("New constraint: " << c);
#if ENABLE_LINEAR_SOLVER
@ -200,8 +199,43 @@ namespace polysat {
}
linear_propagate();
SASSERT(wlist_invariant());
if (!is_conflict())
SASSERT(assignment_invariant());
SASSERT(assignment_invariant());
}
void solver::propagate_watch(sat::literal lit) {
auto& wlist = m_bvars.watch(~lit);
unsigned end = 0;
unsigned sz = wlist.size();
bool flush = false;
for (unsigned j = 0; j < sz && !is_conflict(); ++j) {
clause& cl = *wlist[j];
SASSERT(cl.size() >= 2);
unsigned idx = cl[0] == lit ? 1 : 0;
SASSERT(cl[1 - idx] == lit);
if (flush || m_bvars.is_true(cl[idx])) {
wlist[end++] = &cl;
continue;
}
unsigned i = 2;
for (; i < cl.size() && m_bvars.is_false(cl[i]); ++i);
if (i < cl.size()) {
m_bvars.watch(cl[i]).push_back(&cl);
std::swap(cl[1 - idx], cl[i]);
continue;
}
wlist[end++] = &cl;
if (m_bvars.is_false(cl[idx])) {
set_conflict(cl);
flush = true;
continue;
}
unsigned level = 0;
for (i = 0; i < cl.size(); ++i)
if (cl[i] != lit)
level = std::max(level, m_bvars.level(cl[i]));
assign_bool(level, cl[1 - idx], &cl, nullptr);
}
wlist.shrink(end);
}
void solver::linear_propagate() {
@ -221,11 +255,12 @@ namespace polysat {
signed_constraint c = m_constraints.lookup(lit);
SASSERT(c);
activate_constraint(c);
propagate_watch(lit);
}
void solver::propagate(pvar v) {
LOG_H2("Propagate v" << v);
auto& wlist = m_watch[v];
auto& wlist = m_pwatch[v];
unsigned i = 0, j = 0, sz = wlist.size();
for (; i < sz && !is_conflict(); ++i)
if (!wlist[i].propagate(*this, v))
@ -238,7 +273,7 @@ namespace polysat {
void solver::propagate(pvar v, rational const& val, signed_constraint c) {
LOG("Propagation: " << assignment_pp(*this, v, val) << ", due to " << c);
if (m_viable.is_viable(v, val)) {
m_free_vars.del_var_eh(v);
m_free_pvars.del_var_eh(v);
assign_core(v, val, justification::propagation(m_level));
}
else
@ -288,7 +323,7 @@ namespace polysat {
case trail_instr_t::assign_i: {
auto v = m_search.back().var();
LOG_V("Undo assign_i: v" << v);
m_free_vars.unassign_var_eh(v);
m_free_pvars.unassign_var_eh(v);
m_justification[v] = justification::unassigned();
m_search.pop();
break;
@ -344,7 +379,7 @@ namespace polysat {
void solver::add_watch(signed_constraint c, pvar v) {
SASSERT(c);
LOG("Watching v" << v << " in constraint " << c);
m_watch[v].push_back(c);
m_pwatch[v].push_back(c);
}
void solver::erase_watch(signed_constraint c) {
@ -358,7 +393,7 @@ namespace polysat {
void solver::erase_watch(pvar v, signed_constraint c) {
if (v == null_var)
return;
auto& wlist = m_watch[v];
auto& wlist = m_pwatch[v];
unsigned sz = wlist.size();
for (unsigned i = 0; i < sz; ++i) {
if (c == wlist[i]) {
@ -372,10 +407,13 @@ namespace polysat {
void solver::decide() {
LOG_H2("Decide");
SASSERT(can_decide());
decide(m_free_vars.next_var());
if (!m_free_bvars.empty())
bdecide(m_free_bvars.next_var());
else
pdecide(m_free_pvars.next_var());
}
void solver::decide(pvar v) {
void solver::pdecide(pvar v) {
LOG("Decide v" << v);
IF_LOGGING(m_viable.log(v));
rational val;
@ -384,7 +422,7 @@ namespace polysat {
// NOTE: all such cases should be discovered elsewhere (e.g., during propagation/narrowing)
// (fail here in debug mode so we notice if we miss some)
DEBUG_CODE( UNREACHABLE(); );
m_free_vars.unassign_var_eh(v);
m_free_pvars.unassign_var_eh(v);
set_conflict(v);
break;
case dd::find_t::singleton:
@ -398,6 +436,10 @@ namespace polysat {
}
}
void solver::bdecide(sat::bool_var b) {
}
void solver::assign_core(pvar v, rational const& val, justification const& j) {
if (j.is_decision())
++m_stats.m_num_decisions;
@ -424,6 +466,11 @@ namespace polysat {
m_conflict.set(v);
}
void solver::set_conflict(clause& cl) {
for (auto lit : cl)
set_conflict(~m_constraints.lookup(lit));
}
/**
* Conflict resolution.
* - m_conflict are constraints that are infeasible in the current assignment.
@ -576,8 +623,7 @@ namespace polysat {
if (choice == sat::null_literal) {
// This case may happen when all undefined literals are false under the current variable assignment.
// TODO: The question is whether such lemmas should be generated? Check test_monot() for such a case.
for (auto lit : lemma)
set_conflict(~m_constraints.lookup(lit));
set_conflict(lemma);
return;
}
@ -694,8 +740,7 @@ namespace polysat {
assign_bool(level, lit, reason, nullptr);
}
/// Assign a boolean literal and put it on the search stack,
/// and activate the corresponding constraint.
/// Assign a boolean literal and put it on the search stack
void solver::assign_bool(unsigned level, sat::literal lit, clause* reason, clause* lemma) {
LOG("Assigning boolean literal: " << lit);
m_bvars.assign(lit, level, reason, lemma);
@ -804,7 +849,7 @@ namespace polysat {
}
std::ostream& solver::display(std::ostream& out) const {
out << "Assignment:\n";
out << "Search Stack:\n";
for (auto item : m_search) {
if (item.is_assignment()) {
pvar v = item.var();
@ -894,7 +939,7 @@ namespace polysat {
bool is_positive = value == l_true;
int64_t num_watches = 0;
signed_constraint sc(c, is_positive);
for (auto const& wlist : m_watch) {
for (auto const& wlist : m_pwatch) {
auto n = std::count(wlist.begin(), wlist.end(), sc);
VERIFY(n <= 1); // no duplicates in the watchlist
num_watches += n;
@ -909,14 +954,22 @@ namespace polysat {
/** Check that boolean assignment and constraint evaluation are consistent */
bool solver::assignment_invariant() {
if (is_conflict())
return true;
bool ok = true;
for (sat::bool_var v = m_bvars.size(); v-- > 0; ) {
sat::literal lit(v);
if (m_bvars.value(lit) == l_true)
SASSERT(!m_constraints.lookup(lit).is_currently_false(*this));
if (m_bvars.value(lit) == l_false)
SASSERT(!m_constraints.lookup(lit).is_currently_true(*this));
sat::literal lit(v);
auto c = m_constraints.lookup(lit);
if (!std::all_of(c->vars().begin(), c->vars().end(), [&](auto v) { return is_assigned(v); }))
continue;
ok &= (m_bvars.value(lit) != l_true) || !c.is_currently_false(*this);
ok &= (m_bvars.value(lit) != l_false) || !c.is_currently_true(*this);
if (!ok) {
LOG("assignment invariant is broken " << v << "\n" << *this);
break;
}
}
return true;
return ok;
}
/// Check that all constraints on the stack are satisfied by the current model.