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updates to simplifier

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-10-23 01:00:06 -04:00
parent 42749e7b22
commit ee6cfb8eef
9 changed files with 365 additions and 291 deletions
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112
src/sat/sat_lookahead.cpp
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@ -204,7 +204,7 @@ namespace sat {
void lookahead::pre_select() {
IF_VERBOSE(10, verbose_stream() << "freevars: " << m_freevars.size() << "\n";);
IF_VERBOSE(10, verbose_stream() << "(sat-lookahead :freevars " << m_freevars.size() << ")\n";);
m_lookahead.reset();
for (bool_var x : m_freevars) { // tree lookahead leaves literals fixed in lower truth levels
literal l(x, false);
@ -1808,7 +1808,7 @@ namespace sat {
scoped_level _sl(*this, dl_truth);
SASSERT(get_level(m_trail.back()) == dl_truth);
SASSERT(is_fixed(l));
IF_VERBOSE(2, verbose_stream() << "double: " << l << " depth: " << m_trail_lim.size() << "\n";);
IF_VERBOSE(2, verbose_stream() << "(sat-lookahead :double " << l << " :depth " << m_trail_lim.size() << ")\n";);
lookahead_backtrack();
assign(l);
propagate();
@ -2211,71 +2211,65 @@ namespace sat {
m_s.propagate_core(false);
m_s.m_simplifier(false);
}
if (select(0)) {
get_scc();
if (!inconsistent()) {
normalize_parents();
literal_vector roots;
bool_var_vector to_elim;
for (unsigned i = 0; i < m_num_vars; ++i) {
roots.push_back(literal(i, false));
}
for (auto const& c : m_candidates) {
bool_var v = c.m_var;
literal q(v, false);
literal p = get_parent(q);
if (p != null_literal && p.var() != v && !m_s.is_external(v) &&
!m_s.was_eliminated(v) && !m_s.was_eliminated(p.var())) {
to_elim.push_back(v);
roots[v] = p;
VERIFY(get_parent(p) == p);
VERIFY(get_parent(~p) == ~p);
}
}
IF_VERBOSE(1, verbose_stream() << "(sat-lookahead :equivalences " << to_elim.size() << ")\n";);
elim_eqs elim(m_s);
elim(roots, to_elim);
}
}
m_lookahead.reset();
}
//
// there can be two sets of equivalence classes.
// example:
// a -> !b
// b -> !a
// c -> !a
// we pick as root the Boolean variable with the largest value.
//
literal lookahead::get_root(bool_var v) {
literal lit(v, false);
literal r1 = get_parent(lit);
literal r2 = get_parent(literal(r1.var(), false));
CTRACE("sat", r1 != get_parent(literal(r2.var(), false)),
tout << r1 << " " << r2 << "\n";);
SASSERT(r1.var() == get_parent(literal(r2.var(), false)).var());
if (r1.var() >= r2.var()) {
return r1;
void lookahead::normalize_parents() {
literal_vector roots;
for (unsigned i = 0; i < m_num_vars; ++i) {
literal lit(i, false);
roots.push_back(lit);
roots.push_back(~lit);
SASSERT(roots[lit.index()] == lit);
}
else {
return r1.sign() ? ~r2 : r2;
}
}
/**
\brief extract equivalence classes of variables and simplify clauses using these.
*/
void lookahead::scc() {
SASSERT(m_prefix == 0);
SASSERT(m_watches.empty());
m_search_mode = lookahead_mode::searching;
scoped_level _sl(*this, c_fixed_truth);
init();
if (inconsistent()) return;
inc_istamp();
m_lookahead.reset();
if (select(0)) {
// extract equivalences
get_scc();
if (inconsistent()) return;
literal_vector roots;
bool_var_vector to_elim;
for (unsigned i = 0; i < m_num_vars; ++i) {
roots.push_back(literal(i, false));
}
for (unsigned i = 0; i < m_candidates.size(); ++i) {
bool_var v = m_candidates[i].m_var;
literal p = get_root(v);
if (p != null_literal && p.var() != v && !m_s.is_external(v) &&
!m_s.was_eliminated(v) && !m_s.was_eliminated(p.var())) {
to_elim.push_back(v);
roots[v] = p;
SASSERT(get_parent(p) == p);
set_parent(~p, ~p);
SASSERT(get_parent(~p) == ~p);
for (auto const& c : m_candidates) {
bool_var v = c.m_var;
literal p(v, false);
literal q = get_parent(p);
literal r = ~get_parent(~p);
if (q != r) {
if (q.var() < r.var()) {
roots[q.index()] = r;
}
else {
roots[r.index()] = q;
}
}
IF_VERBOSE(1, verbose_stream() << "(sat-lookahead :equivalences " << to_elim.size() << ")\n";);
elim_eqs elim(m_s);
elim(roots, to_elim);
}
m_lookahead.reset();
for (auto const& c : m_candidates) {
literal p(c.m_var, false);
literal q = roots[get_parent(p).index()];
set_parent(p, q);
set_parent(~p, ~q);
}
}
std::ostream& lookahead::display_summary(std::ostream& out) const {