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fix bugs related to use of lookahead equivalences and encoding of pb constraints

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-05-15 09:33:27 -07:00
parent c49550ff2d
commit 2033e649b5
8 changed files with 115 additions and 70 deletions
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49
src/sat/sat_lookahead.h
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@ -251,19 +251,16 @@ namespace sat {
void del_binary(unsigned idx) {
// TRACE("sat", display(tout << "Delete " << to_literal(idx) << "\n"););
literal_vector & lits = m_binary[idx];
if (lits.empty()) IF_VERBOSE(0, verbose_stream() << "empty literals\n";);
SASSERT(!lits.empty());
literal l = lits.back();
lits.pop_back();
if (m_binary[(~l).index()].back() != ~to_literal(idx)) {
IF_VERBOSE(0, verbose_stream() << "pop bad literal: " << idx << " " << (~l).index() << "\n";);
}
if (m_binary[(~l).index()].empty())
IF_VERBOSE(0, verbose_stream() << "empty binary\n";);
lits.pop_back();
SASSERT(!m_binary[(~l).index()].empty());
IF_VERBOSE(0, if (m_binary[(~l).index()].back() != ~to_literal(idx)) verbose_stream() << "pop bad literal: " << idx << " " << (~l).index() << "\n";);
SASSERT(m_binary[(~l).index()].back() == ~to_literal(idx));
m_binary[(~l).index()].pop_back();
++m_stats.m_del_binary;
}
void validate_binary(literal l1, literal l2) {
if (m_search_mode == lookahead_mode::searching) {
m_assumptions.push_back(l1);
@ -1856,6 +1853,9 @@ namespace sat {
return search();
}
/**
\brief simplify set of clauses by extracting units from a lookahead at base level.
*/
void simplify() {
SASSERT(m_prefix == 0);
SASSERT(m_watches.empty());
@ -1875,12 +1875,38 @@ namespace sat {
++num_units;
}
}
IF_VERBOSE(1, verbose_stream() << "units found: " << num_units << "\n";);
IF_VERBOSE(1, verbose_stream() << "(sat-lookahead :units " << num_units << ")\n";);
m_s.m_simplifier.subsume();
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 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;
}
else {
return r1.sign() ? ~r2 : r2;
}
}
/**
\brief extract equivalence classes of variables and simplify clauses using these.
*/
void scc() {
SASSERT(m_prefix == 0);
SASSERT(m_watches.empty());
@ -1901,14 +1927,13 @@ namespace sat {
}
for (unsigned i = 0; i < m_candidates.size(); ++i) {
bool_var v = m_candidates[i].m_var;
literal lit = literal(v, false);
literal p = get_parent(lit);
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;
}
}
IF_VERBOSE(1, verbose_stream() << "eliminate " << to_elim.size() << " variables\n";);
IF_VERBOSE(1, verbose_stream() << "(sat-lookahead :equivalences " << to_elim.size() << ")\n";);
elim_eqs elim(m_s);
elim(roots, to_elim);
}