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Polysat: conflict resolution updates (#5534)

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* variable elimination / saturation sketch

* conflict resolution updates
This commit is contained in:
Jakob Rath 2021-09-03 19:17:06 +02:00 • committed by GitHub
parent dc547510db
commit 9f387f5738
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14 changed files with 343 additions and 294 deletions
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23
src/math/polysat/conflict_core.h
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@ -17,6 +17,8 @@ Author:
namespace polysat {
class solver;
class inference_engine;
class variable_elimination_engine;
/** Conflict state, represented as core (~negation of clause). */
class conflict_core {
@ -24,6 +26,7 @@ namespace polysat {
// If this is not null_var, the conflict was due to empty viable set for this variable.
// Can be treated like "v = x" for any value x.
// TODO: we could always set this to the variable we're currently focusing on.
pvar m_conflict_var = null_var;
/** True iff the conflict depends on the current variable assignment. (If so, additional constraints must be added to the final learned clause.) */
@ -32,7 +35,17 @@ namespace polysat {
// The drawback is that we may get weaker lemmas in some cases (but they are still correct).
// For example: if we have 4x+y=2 and y=0, then we have a conflict no matter the value of x, so we should drop x=? from the core.
solver* m_solver = nullptr;
constraint_manager& cm();
scoped_ptr_vector<variable_elimination_engine> ve_engines;
scoped_ptr_vector<inference_engine> inf_engines;
// ptr_addr_map<constraint, vector<signed_constraint>> m_saturation_premises;
map<signed_constraint, vector<signed_constraint>, obj_hash<signed_constraint>, default_eq<signed_constraint>> m_saturation_premises;
public:
conflict_core(solver& s);
~conflict_core();
vector<signed_constraint> const& constraints() const { return m_constraints; }
bool needs_model() const { return m_needs_model; }
pvar conflict_var() const { return m_conflict_var; }
@ -47,6 +60,7 @@ namespace polysat {
m_constraints.reset();
m_needs_model = false;
m_conflict_var = null_var;
m_saturation_premises.reset();
SASSERT(empty());
}
@ -57,7 +71,9 @@ namespace polysat {
/** conflict because there is no viable value for the variable v */
void set(pvar v);
void push(signed_constraint c);
void insert(signed_constraint c);
void insert(signed_constraint c, vector<signed_constraint> premises);
void remove(signed_constraint c);
/** Perform boolean resolution with the clause upon variable 'var'.
* Precondition: core/clause contain complementary 'var'-literals.
@ -65,7 +81,10 @@ namespace polysat {
void resolve(constraint_manager const& m, sat::bool_var var, clause const& cl);
/** Convert the core into a lemma to be learned. */
clause_ref build_lemma(solver& s, unsigned trail_idx);
clause_ref build_lemma();
bool try_eliminate(pvar v);
bool try_saturate(pvar v);
using const_iterator = decltype(m_constraints)::const_iterator;
const_iterator begin() { return constraints().begin(); }