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gt encoding of pb constraints

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2017-04-16 12:07:16 +09:00
parent b70096a97f
commit 41e1b9f3fe
2 changed files with 183 additions and 17 deletions
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54
src/sat/sat_lookahead.h
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@ -282,8 +282,10 @@ namespace sat {
inc_bstamp();
set_bstamp(l);
literal_vector const& conseq = m_binary[l.index()];
for (unsigned i = 0; i < conseq.size(); ++i) {
set_bstamp(conseq[i]);
literal_vector::const_iterator it = conseq.begin();
literal_vector::const_iterator end = conseq.end();
for (; it != end; ++it) {
set_bstamp(*it);
}
}
bool is_stamped(literal l) const { return m_bstamp[l.index()] == m_bstamp_id; }
@ -557,6 +559,7 @@ namespace sat {
literal_vector::iterator it = m_binary[l.index()].begin(), end = m_binary[l.index()].end();
for (; it != end; ++it) {
if (is_undef(*it)) sum += h[it->index()];
// if (m_freevars.contains(it->var())) sum += h[it->index()];
}
watch_list& wlist = m_watches[l.index()];
watch_list::iterator wit = wlist.begin(), wend = wlist.end();
@ -568,9 +571,8 @@ namespace sat {
case watched::TERNARY: {
literal l1 = wit->get_literal1();
literal l2 = wit->get_literal2();
if (is_undef(l1) && is_undef(l2)) {
tsum += h[l1.index()] * h[l2.index()];
}
// if (is_undef(l1) && is_undef(l2))
tsum += h[l1.index()] * h[l2.index()];
break;
}
case watched::CLAUSE: {
@ -1155,14 +1157,19 @@ namespace sat {
// convert windfalls to binary clauses.
if (!unsat) {
literal nlit = ~lit;
for (unsigned i = 0; i < m_wstack.size(); ++i) {
++m_stats.m_windfall_binaries;
literal l2 = m_wstack[i];
//update_prefix(~lit);
//update_prefix(m_wstack[i]);
TRACE("sat", tout << "windfall: " << nlit << " " << l2 << "\n";);
// if we use try_add_binary, then this may produce new assignments
// these assignments get put on m_trail, and they are cleared by
// reset_wnb. We would need to distinguish the trail that comes
// from lookahead levels and the main search level for this to work.
add_binary(nlit, l2);
}
m_stats.m_windfall_binaries += m_wstack.size();
}
m_wstack.reset();
}
@ -1180,6 +1187,15 @@ namespace sat {
return r;
}
//
// The current version is modeled after CDCL SAT solving data-structures.
// It borrows from the watch list data-structure. The cost tradeoffs are somewhat
// biased towards CDCL search overheads.
// If we walk over the positive occurrences of l, then those clauses can be retired so
// that they don't interfere with calculation of H. Instead of removing clauses from the watch
// list one can swap them to the "back" and adjust a size indicator of the watch list
// Only the size indicator needs to be updated on backtracking.
//
void propagate_clauses(literal l) {
SASSERT(is_true(l));
if (inconsistent()) return;
@ -1237,17 +1253,17 @@ namespace sat {
break;
}
case watched::CLAUSE: {
clause_offset cls_off = it->get_clause_offset();
clause & c = *(s.m_cls_allocator.get_clause(cls_off));
if (is_true(it->get_blocked_literal())) {
*it2 = *it;
++it2;
break;
}
clause_offset cls_off = it->get_clause_offset();
clause & c = *(s.m_cls_allocator.get_clause(cls_off));
if (c[0] == ~l)
std::swap(c[0], c[1]);
if (is_true(c[0])) {
it->set_blocked_literal(c[0]);
*it2 = *it;
it2++;
break;
@ -1337,13 +1353,21 @@ namespace sat {
}
void propagate() {
for (; m_qhead < m_trail.size(); ++m_qhead) {
if (inconsistent()) break;
literal l = m_trail[m_qhead];
TRACE("sat", tout << "propagate " << l << " @ " << m_level << "\n";);
propagate_binary(l);
propagate_clauses(l);
while (!inconsistent() && m_qhead < m_trail.size()) {
unsigned i = m_qhead;
unsigned sz = m_trail.size();
for (; i < sz && !inconsistent(); ++i) {
literal l = m_trail[i];
TRACE("sat", tout << "propagate " << l << " @ " << m_level << "\n";);
propagate_binary(l);
}
i = m_qhead;
for (; i < sz && !inconsistent(); ++i) {
propagate_clauses(m_trail[i]);
}
m_qhead = sz;
}
TRACE("sat_verbose", display(tout << scope_lvl() << " " << (inconsistent()?"unsat":"sat") << "\n"););
}