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allow propagation on equalities and literals that are not assigned.

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This commit is contained in:
Nikolaj Bjorner 2023-12-07 19:43:08 -08:00
parent 9df89e1640
commit bb03f1f1ec
5 changed files with 114 additions and 60 deletions
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102
src/sat/smt/polysat_core.cpp
View file

@ -66,16 +66,16 @@ namespace polysat {
class core::mk_add_watch : public trail {
core& c;
unsigned m_idx;
public:
mk_add_watch(core& c, unsigned idx) : c(c), m_idx(idx) {}
mk_add_watch(core& c) : c(c) {}
void undo() override {
auto& sc = c.m_prop_queue[m_idx].first;
auto& [sc, lit] = c.m_constraint_trail.back();
auto& vars = sc.vars();
if (vars.size() > 0)
c.m_watch[vars[0]].pop_back();
if (vars.size() > 1)
c.m_watch[vars[1]].pop_back();
c.m_constraint_trail.pop_back();
}
};
@ -123,6 +123,22 @@ namespace polysat {
m_var_queue.del_var_eh(v);
}
unsigned core::register_constraint(signed_constraint& sc, solver_assertion as) {
unsigned idx = m_constraint_trail.size();
m_constraint_trail.push_back({ sc, as });
auto& vars = sc.vars();
unsigned i = 0, j = 0, sz = vars.size();
for (; i < sz && j < 2; ++i)
if (!is_assigned(vars[i]))
std::swap(vars[i], vars[j++]);
if (vars.size() > 0)
add_watch(idx, vars[0]);
if (vars.size() > 1)
add_watch(idx, vars[1]);
s.ctx.push(mk_add_watch(*this));
return idx;
}
// case split on unassigned variables until all are assigned values.
// create equality literal for unassigned variable.
// return new_eq if there is a new literal.
@ -141,6 +157,7 @@ namespace polysat {
s.propagate(m_constraints.eq(var2pdd(m_var), m_value), m_viable.explain());
return sat::check_result::CR_CONTINUE;
case find_t::multiple:
s.add_eq_literal(m_var, m_value);
return sat::check_result::CR_CONTINUE;
case find_t::resource_out:
return sat::check_result::CR_GIVEUP;
@ -155,33 +172,17 @@ namespace polysat {
return false;
s.ctx.push(value_trail(m_qhead));
for (; m_qhead < m_prop_queue.size() && !s.ctx.inconsistent(); ++m_qhead)
propagate_constraint(m_qhead, m_prop_queue[m_qhead]);
propagate_constraint(m_prop_queue[m_qhead]);
s.ctx.push(value_trail(m_vqhead));
for (; m_vqhead < m_prop_queue.size() && !s.ctx.inconsistent(); ++m_vqhead)
propagate_value(m_vqhead, m_prop_queue[m_vqhead]);
propagate_value(m_prop_queue[m_vqhead]);
return true;
}
void core::propagate_constraint(unsigned idx, dependent_constraint& dc) {
auto [sc, dep] = dc;
if (sc.is_eq(m_var, m_value)) {
void core::propagate_constraint(prop_item& dc) {
auto [idx, sc, dep] = dc;
if (sc.is_eq(m_var, m_value))
propagate_assignment(m_var, m_value, dep);
return;
}
add_watch(idx, sc);
}
void core::add_watch(unsigned idx, signed_constraint& sc) {
auto& vars = sc.vars();
unsigned i = 0, j = 0, sz = vars.size();
for (; i < sz && j < 2; ++i)
if (!is_assigned(vars[i]))
std::swap(vars[i], vars[j++]);
if (vars.size() > 0)
add_watch(idx, vars[0]);
if (vars.size() > 1)
add_watch(idx, vars[1]);
s.ctx.push(mk_add_watch(*this, idx));
}
void core::add_watch(unsigned idx, unsigned var) {
@ -205,7 +206,7 @@ namespace polysat {
// for entries where there is only one free variable left add to viable set
unsigned j = 0;
for (auto idx : m_watch[v]) {
auto [sc, dep] = m_prop_queue[idx];
auto [sc, as] = m_constraint_trail[idx];
auto& vars = sc.vars();
if (vars[0] != v)
std::swap(vars[0], vars[1]);
@ -219,39 +220,51 @@ namespace polysat {
break;
}
}
if (!swapped) {
m_watch[v][j++] = idx;
}
// constraint is unitary, add to viable set
if (vars.size() >= 2 && is_assigned(vars[0]) && !is_assigned(vars[1])) {
m_viable.add_unitary(vars[1], idx);
}
SASSERT(!swapped || vars.size() <= 1 || (!is_assigned(vars[0]) && !is_assigned(vars[1])));
if (swapped)
continue;
m_watch[v][j++] = idx;
if (vars.size() <= 1)
continue;
auto v1 = vars[1];
if (is_assigned(v1))
continue;
SASSERT(is_assigned(vars[0]) && vars.size() >= 2);
// detect unitary, add to viable, detect conflict?
m_viable.add_unitary(v1, idx);
}
m_watch[v].shrink(j);
}
void core::propagate_value(unsigned idx, dependent_constraint const& dc) {
auto [sc, dep] = dc;
void core::propagate_value(prop_item const& dc) {
auto [idx, sc, dep] = dc;
// check if sc evaluates to false
switch (eval(sc)) {
case l_true:
return;
case l_false:
m_unsat_core = explain_eval(dc);
m_unsat_core = explain_eval({ sc, dep });
propagate_unsat_core();
return;
default:
break;
}
// if sc is v == value, then check the watch list for v if they evaluate to false.
// if sc is v == value, then check the watch list for v to propagate truth assignments
if (sc.is_eq(m_var, m_value)) {
for (auto idx : m_watch[m_var]) {
auto [sc, dep] = m_prop_queue[idx];
if (eval(sc) == l_false) {
m_unsat_core = explain_eval({ sc, dep });
propagate_unsat_core();
return;
auto [sc, as] = m_constraint_trail[idx];
switch (eval(sc)) {
case l_false:
m_unsat_core = explain_eval({ sc, nullptr });
s.propagate(as, true, m_unsat_core);
break;
case l_true:
m_unsat_core = explain_eval({ sc, nullptr });
s.propagate(as, false, m_unsat_core);
break;
default:
break;
}
}
}
@ -259,15 +272,14 @@ namespace polysat {
throw default_exception("nyi");
}
bool core::propagate_unsat_core() {
void core::propagate_unsat_core() {
// default is to use unsat core:
s.set_conflict(m_unsat_core);
// if core is based on viable, use s.set_lemma();
throw default_exception("nyi");
}
void core::assign_eh(signed_constraint const& sc, dependency const& dep) {
m_prop_queue.push_back({ sc, m_dep.mk_leaf(dep) });
void core::assign_eh(unsigned index, signed_constraint const& sc, dependency const& dep) {
m_prop_queue.push_back({ index, sc, m_dep.mk_leaf(dep) });
s.ctx.push(push_back_vector(m_prop_queue));
}

26
src/sat/smt/polysat_core.h
View file

@ -30,12 +30,25 @@ namespace polysat {
class core;
class solver;
struct solver_assertion {
unsigned m_var1;
unsigned m_var2 = 0;
public:
solver_assertion(sat::literal lit) : m_var1(2*lit.index()) {}
solver_assertion(unsigned v1, unsigned v2) : m_var1(1 + 2*v1), m_var2(v2) {}
bool is_literal() const { return m_var1 % 2 == 0; }
sat::literal get_literal() const { SASSERT(is_literal()); return sat::to_literal(m_var1 / 2); }
unsigned var1() const { SASSERT(!is_literal()); return (m_var1 - 1) / 2; }
unsigned var2() const { SASSERT(!is_literal()); return m_var2; }
};
class core {
class mk_add_var;
class mk_dqueue_var;
class mk_assign_var;
class mk_add_watch;
typedef svector<std::pair<unsigned, unsigned>> activity;
typedef std::tuple<unsigned, signed_constraint, stacked_dependency*> prop_item;
friend class viable;
friend class constraints;
friend class assignment;
@ -45,7 +58,8 @@ namespace polysat {
constraints m_constraints;
assignment m_assignment;
unsigned m_qhead = 0, m_vqhead = 0;
svector<dependent_constraint> m_prop_queue;
svector<prop_item> m_prop_queue;
svector<std::tuple<signed_constraint, solver_assertion>> m_constraint_trail; //
stacked_dependency_manager<dependency> m_dep;
mutable scoped_ptr_vector<dd::pdd_manager> m_pdd;
dependency_vector m_unsat_core;
@ -69,12 +83,11 @@ namespace polysat {
void del_var();
bool is_assigned(pvar v) { return nullptr != m_justification[v]; }
void propagate_constraint(unsigned idx, dependent_constraint& dc);
void propagate_value(unsigned idx, dependent_constraint const& dc);
void propagate_constraint(prop_item& dc);
void propagate_value(prop_item const& dc);
void propagate_assignment(pvar v, rational const& value, stacked_dependency* dep);
bool propagate_unsat_core();
void propagate_unsat_core();
void add_watch(unsigned idx, signed_constraint& sc);
void add_watch(unsigned idx, unsigned var);
lbool eval(signed_constraint sc) { throw default_exception("nyi"); }
@ -85,8 +98,9 @@ namespace polysat {
sat::check_result check();
unsigned register_constraint(signed_constraint& sc, solver_assertion sa);
bool propagate();
void assign_eh(signed_constraint const& sc, dependency const& dep);
void assign_eh(unsigned idx, signed_constraint const& sc, dependency const& dep);
expr_ref constraint2expr(signed_constraint const& sc) const { throw default_exception("nyi"); }

11
src/sat/smt/polysat_internalize.cpp
View file

@ -169,12 +169,15 @@ namespace polysat {
}
};
solver::atom* solver::mk_atom(sat::bool_var bv) {
solver::atom* solver::mk_atom(sat::literal lit, signed_constraint& sc) {
auto bv = lit.var();
atom* a = get_bv2a(bv);
if (a)
return a;
a = new (get_region()) atom(bv);
insert_bv2a(bv, a);
a->m_sc = sc;
a->m_index = m_core.register_constraint(sc, lit);
ctx.push(mk_atom_trail(bv, *this));
return a;
}
@ -184,7 +187,7 @@ namespace polysat {
auto q = expr2pdd(e->get_arg(1));
auto sc = ~fn(p, q);
sat::literal lit = expr2literal(e);
mk_atom(lit.var())->m_sc = sc;
auto* a = mk_atom(lit, sc);
}
void solver::internalize_div_rem_i(app* e, bool is_div) {
@ -277,6 +280,7 @@ namespace polysat {
template<bool Signed, bool Rev, bool Negated>
void solver::internalize_le(app* e) {
SASSERT(e->get_num_args() == 2);
auto p = expr2pdd(e->get_arg(0));
auto q = expr2pdd(e->get_arg(1));
if (Rev)
@ -286,8 +290,7 @@ namespace polysat {
sc = ~sc;
sat::literal lit = expr2literal(e);
atom* a = mk_atom(lit.var());
a->m_sc = sc;
atom* a = mk_atom(lit, sc);
}
void solver::internalize_bit2bool(atom* a, expr* e, unsigned idx) {

30
src/sat/smt/polysat_solver.cpp
View file

@ -66,7 +66,7 @@ namespace polysat {
auto sc = a->m_sc;
if (l.sign())
sc = ~sc;
m_core.assign_eh(sc, dependency(l, s().lvl(l)));
m_core.assign_eh(a->m_index, sc, dependency(l, s().lvl(l)));
}
void solver::set_conflict(dependency_vector const& core) {
@ -151,8 +151,10 @@ namespace polysat {
pdd q = var2pdd(v2);
auto sc = m_core.eq(p, q);
m_var_eqs.setx(m_var_eqs_head, std::make_pair(v1, v2), std::make_pair(v1, v2));
ctx.push(value_trail<unsigned>(m_var_eqs_head));
m_core.assign_eh(sc, dependency(m_var_eqs_head, s().scope_lvl()));
ctx.push(value_trail<unsigned>(m_var_eqs_head));
unsigned index = 0;
// unsigned index = m_core.register_constraint(sc);
m_core.assign_eh(index, sc, dependency(m_var_eqs_head, s().scope_lvl()));
m_var_eqs_head++;
}
@ -162,8 +164,9 @@ namespace polysat {
pdd q = var2pdd(v2);
auto sc = ~m_core.eq(p, q);
sat::literal neq = ~expr2literal(ne.eq());
auto index = m_core.register_constraint(sc, neq);
TRACE("bv", tout << neq << " := " << s().value(neq) << " @" << s().scope_lvl() << "\n");
m_core.assign_eh(sc, dependency(neq, s().lvl(neq)));
m_core.assign_eh(index, sc, dependency(neq, s().lvl(neq)));
}
// Core uses the propagate callback to add unit propagations to the trail.
@ -176,6 +179,25 @@ namespace polysat {
ctx.propagate(lit, ex);
}
void solver::propagate(solver_assertion as, bool sign, dependency_vector const& deps) {
auto [core, eqs] = explain_deps(deps);
if (as.is_literal()) {
auto lit = as.get_literal();
if (sign)
lit.neg();
auto ex = euf::th_explain::propagate(*this, core, eqs, lit, nullptr);
ctx.propagate(lit, ex);
}
else if (sign) {
// equalities are always asserted so a negative propagation is a conflict.
auto n1 = var2enode(as.var1());
auto n2 = var2enode(as.var2());
eqs.push_back({ n1, n2 });
auto ex = euf::th_explain::conflict(*this, core, eqs, nullptr);
ctx.set_conflict(ex);
}
}
void solver::add_lemma(vector<signed_constraint> const& lemma) {
sat::literal_vector lits;
for (auto sc : lemma)

5
src/sat/smt/polysat_solver.h
View file

@ -42,6 +42,7 @@ namespace polysat {
struct atom {
bool_var m_bv;
unsigned m_index = 0;
signed_constraint m_sc;
atom(bool_var b) :m_bv(b) {}
~atom() { }
@ -91,7 +92,7 @@ namespace polysat {
void erase_bv2a(bool_var bv) { m_bool_var2atom[bv] = nullptr; }
atom* get_bv2a(bool_var bv) const { return m_bool_var2atom.get(bv, nullptr); }
class mk_atom_trail;
atom* mk_atom(sat::bool_var bv);
atom* mk_atom(sat::literal lit, signed_constraint& sc);
void set_bit_eh(theory_var v, literal l, unsigned idx);
void init_bits(expr* e, expr_ref_vector const & bits);
void mk_bits(theory_var v);
@ -133,6 +134,8 @@ namespace polysat {
void set_conflict(dependency_vector const& core);
void set_lemma(vector<signed_constraint> const& lemma, unsigned level, dependency_vector const& core);
void propagate(signed_constraint sc, dependency_vector const& deps);
void propagate(solver_assertion as, bool sign, dependency_vector const& deps);
void add_lemma(vector<signed_constraint> const& lemma);
std::pair<sat::literal_vector, euf::enode_pair_vector> explain_deps(dependency_vector const& deps);