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fixes to trim

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Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2022-10-05 04:32:00 +02:00
parent c1c659dc93
commit f8ca692dee
2 changed files with 85 additions and 92 deletions
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166
src/sat/sat_proof_trim.cpp
View file

@ -26,47 +26,13 @@ namespace sat {
/**
Pseudo-code from Gurfinkel, Vizel, FMCAD 2014
Input: trail (a0,d0), ..., (an,dn) = ({},bot)
Output: reduced trail - result
result = []
C = { an }
for i = n to 0 do
if s.is_deleted(ai) then s.revive(ai)
else
if s.isontrail(ai) then
s.undotrailcore(ai,C)
s.delete(ai)
if ai in C then
if ai is not initial then
s.savetrail()
s.enqueue(not ai)
c = s.propagate()
s.conflictanalysiscore(c, C)
s.restoretrail()
result += [ai]
reverse(result)
is_deleted(ai):
clause was detached
revive(ai):
attach clause ai
isontrail(ai):
some literal on the current trail in s is justified by ai
undotrailcore(ai, C):
pop the trail until dependencies on ai are gone
savetrail:
store current trail so it can be restored
enqueue(not ai):
assert negations of ai at a new decision level
conflictanalysiscore(c, C):
?
restoretrail:
restore the trail to the position before enqueue
Output: reduced trail - result
*/
void proof_trim::trim() {
vector<literal_vector> result, clauses;
clauses.push_back(literal_vector());
vector<literal_vector> proof_trim::trim() {
vector<literal_vector> result;
m_core_literals.reset();
m_core_literals.insert(literal_vector());
for (unsigned i = m_trail.size(); i-- > 0; ) {
auto const& [cl, clp, is_add, is_initial] = m_trail[i];
if (!is_add) {
@ -75,22 +41,15 @@ namespace sat {
}
prune_trail(cl, clp);
del(cl, clp);
if (!clauses.contains(cl))
if (!in_core(cl, clp))
continue;
result.push_back(cl);
if (is_initial)
continue;
s.push();
unsigned init_sz = s.m_trail.size();
unsigned lvl = s.scope_lvl();
for (auto lit : cl)
s.assign(~lit, justification(lvl));
s.propagate(false);
SASSERT(s.inconsistent());
conflict_analysis_core(init_sz, clauses);
s.pop(1);
conflict_analysis_core(cl, clp);
}
result.reverse();
return result;
}
void proof_trim::del(literal_vector const& cl, clause* cp) {
@ -176,14 +135,15 @@ namespace sat {
The current state is in conflict.
Chase justifications for conflict to extract clauses that are in coi of conflict.
Assume:
F | G, ~C |- []
Let T (trail) be the extension of G, ~C that derives the empty clause.
T := G, ~C, l1:j1, l2:j2, ..., lk:jk
The goal is to extract clauses in T that are used to derive C.
- some of the literals in ~C that are not set to true already (they must be unassigned relative)
are used to derive the empty clause.
- some literals in ~C that are assigned to true may also be used to derive the empty clause.
This is achieved by collecting all literals from j1, j2, ... jk
and the conflict clause that are at level below ~C and using the clauses that justify those literals.
Example:
C = c or d or e
@ -197,44 +157,67 @@ namespace sat {
queried for their explanation. Their explanation is added to the clauses.
*/
void proof_trim::conflict_analysis_core(unsigned init_sz, vector<literal_vector>& clauses) {
justification j = s.m_conflict;
literal consequent = null_literal;
unsigned idx = s.m_trail.size() - 1;
unsigned old_sz = s.m_unmark.size();
bool_var c_var;
auto add_dependency = [&](bool_var v) {
auto j = s.m_justification[v];
literal lit = literal(v, s.value(v) == l_false);
add_core(lit, j, clauses);
};
if (s.m_not_l != null_literal) {
s.process_antecedent_for_unsat_core(s.m_not_l);
add_core(s.m_not_l, s.m_justification[s.m_not_l.var()], clauses);
add_core(~s.m_not_l, j, clauses);
consequent = ~s.m_not_l;
void proof_trim::conflict_analysis_core(literal_vector const& cl, clause* cp) {
s.push();
unsigned lvl = s.scope_lvl();
for (auto lit : cl)
s.assign(~lit, justification(lvl));
unsigned trail_size0 = s.m_trail.size();
s.push();
s.propagate(false);
if (!s.inconsistent()) {
s.m_qhead = 0;
s.propagate(false);
}
while (true) {
s.process_consequent_for_unsat_core(consequent, j);
while (idx >= init_sz) {
consequent = s.m_trail[idx];
c_var = consequent.var();
if (s.is_marked(c_var))
break;
--idx;
SASSERT(s.inconsistent());
auto add_dependency = [&](literal lit) {
bool_var v = lit.var();
if (s.lvl(v) == 0) {
// inefficient for repeated insertions ?
auto j = s.m_justification[v];
literal lit = literal(v, s.value(v) == l_false);
add_core(lit, j);
}
if (idx < init_sz)
else if (s.lvl(v) == 2)
s.mark(v);
};
auto add_jdependency = [&](justification j) {
switch (j.get_kind()) {
case justification::BINARY:
add_dependency(j.get_literal());
break;
j = s.m_justification[c_var];
--idx;
case justification::TERNARY:
add_dependency(j.get_literal1());
add_dependency(j.get_literal2());
break;
case justification::CLAUSE:
for (auto lit : s.get_clause(j))
if (s.value(lit) == l_false)
add_dependency(lit);
break;
default:
break;
}
};
if (s.m_not_l != null_literal)
add_dependency(s.m_not_l);
add_jdependency(s.m_conflict);
for (unsigned i = s.m_trail.size(); i-- > trail_size0; ) {
bool_var v = s.m_trail[i].var();
if (!s.is_marked(v))
continue;
s.reset_mark(v);
add_jdependency(s.m_justification[v]);
}
for (unsigned i = s.m_mark.size(); i-- > old_sz; )
add_dependency(s.m_unmark[i]);
s.reset_unmark(old_sz);
s.pop(2);
}
void proof_trim::add_core(literal l, justification j, vector<literal_vector>& clauses) {
void proof_trim::add_core(literal l, justification j) {
m_clause.reset();
switch (j.get_kind()) {
case justification::NONE:
@ -248,18 +231,23 @@ namespace sat {
m_clause.push_back(j.get_literal1());
m_clause.push_back(j.get_literal2());
break;
case justification::CLAUSE:
for (auto lit : s.get_clause(j))
m_clause.push_back(lit);
break;
case justification::CLAUSE:
s.get_clause(j).mark_used();
return;
default:
UNREACHABLE();
break;
}
std::sort(m_clause.begin(), m_clause.end());
clauses.insert(m_clause);
m_core_literals.insert(m_clause);
}
bool proof_trim::in_core(literal_vector const& cl, clause* cp) const {
if (cp)
return cp->was_used();
else
return m_core_literals.contains(cl);
}
void proof_trim::revive(literal_vector const& cl, clause* cp) {
if (cp)

11
src/sat/sat_proof_trim.h
View file

@ -35,6 +35,7 @@ namespace sat {
uint_set m_in_coi;
vector<std::tuple<literal_vector, clause*, bool, bool>> m_trail;
struct hash {
unsigned operator()(literal_vector const& v) const {
return string_hash((char const*)v.begin(), v.size()*sizeof(literal), 3);
@ -47,17 +48,21 @@ namespace sat {
};
map<literal_vector, clause_vector, hash, eq> m_clauses;
hashtable<literal_vector, hash, eq> m_core_literals;
void del(literal_vector const& cl, clause* cp);
bool match_clause(literal_vector const& cl, literal l1, literal l2) const;
bool match_clause(literal_vector const& cl, literal l1, literal l2, literal l3) const;
void prune_trail(literal_vector const& cl, clause* cp);
void conflict_analysis_core(unsigned init_sz, vector<literal_vector>& clauses);
void add_core(literal l, justification j, vector<literal_vector>& clauses);
void conflict_analysis_core(literal_vector const& cl, clause* cp);
void add_core(literal l, justification j);
bool in_core(literal_vector const& cl, clause* cp) const;
void revive(literal_vector const& cl, clause* cp);
clause* del(literal_vector const& cl);
void save(literal_vector const& lits, clause* cl);
public:
@ -73,7 +78,7 @@ namespace sat {
void infer();
void updt_params(params_ref const& p) { s.updt_params(p); }
void trim();
vector<literal_vector> trim();
};
}