box contractor_int::prune(box b, SMTConfig & config) const {
// ======= Proof =======
thread_local static box old_box(b);
if (config.nra_proof) { old_box = b; }
m_input = ibex::BitSet::empty(b.size());
m_output = ibex::BitSet::empty(b.size());
unsigned i = 0;
ibex::IntervalVector & iv = b.get_values();
for (Enode * e : b.get_vars()) {
if (e->hasSortInt()) {
auto old_iv = iv[i];
iv[i] = ibex::integer(iv[i]);
if (old_iv != iv[i]) {
m_input.add(i);
m_output.add(i);
}
if (iv[i].is_empty()) {
b.set_empty();
break;
}
}
i++;
}
// ======= Proof =======
if (config.nra_proof) {
output_pruning_step(config.nra_proof_out, old_box, b, config.nra_readable_proof, "integer pruning");
}
return b;
}
contractor_int::contractor_int(box const & b) : contractor_cell(contractor_kind::INT) {
m_input = ibex::BitSet::empty(b.size());
auto const & vars = b.get_vars();
for (unsigned i = 0; i < b.size(); ++i) {
Enode * const e = vars[i];
if (e->hasSortInt()) {
m_input.add(i);
}
}
}
box shrink_for_dop(box b) {
for (Enode * e : b.get_vars()) {
string const name = e->getCar()->getNameFull();
if (starts_with(name, "forall_")) {
string const exist_var_name = name.substr(7);
auto exist_var_intv = b[exist_var_name];
b[name] = exist_var_intv;
}
}
return b;
}
box refine_CE_with_nlopt_core(box counterexample, vector<Enode*> const & opt_ctrs, vector<Enode*> const & side_ctrs) {
// Plug-in `a` into the constraint and optimize `b` in the counterexample `M` by solving:
//
// ∃ y_opt ∈ I_y. ∀ y ∈ I_y. f(a, y_opt) >= f(a, y) — (2)
//
// using local optimizer (i.e. nlopt).
// Let `M’ = (a, b_opt)` be a model for (2).
DREAL_LOG_DEBUG << "================================" << endl;
DREAL_LOG_DEBUG << " Before Refinement " << endl;
DREAL_LOG_DEBUG << "================================" << endl;
DREAL_LOG_DEBUG << counterexample << endl;
DREAL_LOG_DEBUG << "================================" << endl;
static bool initialized = false;
static vector<double> lb, ub, init;
init.clear();
for (Enode * e : counterexample.get_vars()) {
if (e->isForallVar()) {
if (!initialized) {
lb.push_back(e->getDomainLowerBound());
ub.push_back(e->getDomainUpperBound());
}
init.push_back(counterexample[e].mid());
DREAL_LOG_DEBUG << lb.back() << " <= " << init.back() << " <= " << ub.back() << endl;
}
}
auto const n = init.size();
static nlopt::opt opt(nlopt::LD_SLSQP, n);
if (!initialized) {
opt.set_lower_bounds(lb);
opt.set_upper_bounds(ub);
// set tollerance
// TODO(soonhok): set precision
// opt.set_xtol_rel(0.0001);
opt.set_xtol_abs(0.001);
opt.set_maxtime(0.01);
initialized = true;
}
opt.remove_equality_constraints();
opt.remove_inequality_constraints();
// set objective function
vector<tuple<Enode *, box const &, bool> *> extra_vec;
Enode * e = opt_ctrs[0];
bool polarity = false;
while (e->isNot()) {
e = e->get1st();
polarity = !polarity;
}
auto extra = new tuple<Enode *, box const &, bool>(e, counterexample, polarity);
extra_vec.push_back(extra);
opt.set_min_objective(nlopt_obj, extra);
opt.add_inequality_constraint(nlopt_side_condition, extra);
DREAL_LOG_DEBUG << "objective function is added: " << e << endl;
// set side conditions
for (Enode * e : side_ctrs) {
bool polarity = false;
while (e->isNot()) {
e = e->get1st();
polarity = !polarity;
}
auto extra = new tuple<Enode *, box const &, bool>(e, counterexample, polarity);
extra_vec.push_back(extra);
DREAL_LOG_DEBUG << "refine_counterexample_with_nlopt: Side condition is added: " << e << endl;
if (e->isEq()) {
opt.add_equality_constraint(nlopt_side_condition, extra);
} else if (e->isLt() || e->isLeq() || e->isGt() || e->isGeq()) {
opt.add_inequality_constraint(nlopt_side_condition, extra);
}
}
try {
vector<double> output = opt.optimize(init);
unsigned i = 0;
for (Enode * e : counterexample.get_vars()) {
if (e->isForallVar()) {
counterexample[e] = output[i];
i++;
}
}
} catch (nlopt::roundoff_limited & e) {
} catch (std::runtime_error & e) {
DREAL_LOG_DEBUG << e.what() << endl;
}
for (auto extra : extra_vec) {
delete extra;
}
DREAL_LOG_DEBUG << "================================" << endl;
DREAL_LOG_DEBUG << " After Refinement " << endl;
DREAL_LOG_DEBUG << "================================" << endl;
DREAL_LOG_DEBUG << counterexample << endl;
DREAL_LOG_DEBUG << "================================" << endl;
return counterexample;
}
contractor default_strategy::build_contractor(box const & box,
scoped_vec<shared_ptr<constraint>> const & ctrs,
bool const complete,
SMTConfig const & config) const {
bool const use_cache = true;
// 1. Categorize constraints
vector<shared_ptr<nonlinear_constraint>> nl_ctrs;
vector<shared_ptr<ode_constraint>> ode_ctrs_rev;
vector<shared_ptr<generic_forall_constraint>> generic_forall_ctrs;
for (shared_ptr<constraint> const ctr : ctrs.get_reverse()) {
switch (ctr->get_type()) {
case constraint_type::Nonlinear: {
auto nl_ctr = dynamic_pointer_cast<nonlinear_constraint>(ctr);
nl_ctrs.push_back(nl_ctr);
break;
}
case constraint_type::ODE: {
auto ode_ctr = dynamic_pointer_cast<ode_constraint>(ctr);
ode_ctrs_rev.push_back(ode_ctr);
break;
}
case constraint_type::GenericForall: {
auto gf_ctr = dynamic_pointer_cast<generic_forall_constraint>(ctr);
generic_forall_ctrs.push_back(gf_ctr);
break;
}
case constraint_type::ForallT: {
// Do nothing
break;
}
default:
DREAL_LOG_FATAL << "Unknown Constraint Type: " << ctr->get_type() << " " << *ctr << endl;
}
}
vector<shared_ptr<ode_constraint>> ode_ctrs(ode_ctrs_rev);
reverse(ode_ctrs.begin(), ode_ctrs.end());
vector<contractor> ctcs;
ctcs.reserve(ctrs.size());
// 2.0 Build Sample Contractor
if (config.nra_sample > 0 && complete) {
ctcs.push_back(mk_contractor_sample(box, config.nra_sample, ctrs.get_vec()));
}
// 2.1 Build nonlinear contractors
vector<contractor> nl_ctcs;
for (auto const & nl_ctr : nl_ctrs) {
if (!nl_ctr->is_neq()) {
nl_ctcs.push_back(mk_contractor_ibex_fwdbwd(nl_ctr, use_cache));
} else {
// Case: != (not equal), do nothing
}
}
contractor nl_ctc = mk_contractor_seq(nl_ctcs);
ctcs.insert(ctcs.end(), nl_ctcs.begin(), nl_ctcs.end());
// 2.2. Build Polytope Contractor
if (config.nra_polytope) {
ctcs.push_back(mk_contractor_ibex_polytope(config.nra_precision, box.get_vars(), nl_ctrs));
}
// 2.3. Int Contractor
ctcs.push_back(mk_contractor_int(box));
// 2.4. Build generic forall contractors
for (auto const & generic_forall_ctr : generic_forall_ctrs) {
ctcs.push_back(mk_contractor_generic_forall(box, generic_forall_ctr));
}
if (complete && ode_ctrs.size() > 0) {
// Add ODE Contractors only for complete check
// 2.5. Build GSL Contractors (using CAPD4)
vector<contractor> ode_gsl_ctcs;
if (config.nra_ODE_sampling) {
// 2.5.1 Build Eval contractors
vector<contractor> eval_ctcs;
for (auto const & nl_ctr : nl_ctrs) {
eval_ctcs.push_back(mk_contractor_eval(nl_ctr, false));
}
contractor eval_ctc = mk_contractor_seq(eval_ctcs);
if (config.nra_parallel) {
vector<contractor> nl_ctcs2;
for (auto const & nl_ctr : nl_ctrs) {
if (!nl_ctr->is_neq()) {
nl_ctcs2.push_back(mk_contractor_ibex_fwdbwd(nl_ctr, false));
} else {
// Case: != (not equal), do nothing
}
}
contractor nl_ctc2 = mk_contractor_seq(nl_ctcs2);
for (auto const & ode_ctr : ode_ctrs) {
// Add Forward ODE Pruning (Underapproximation, using GNU GSL)
ode_gsl_ctcs.push_back(mk_contractor_gsl(box, ode_ctr, eval_ctc, ode_direction::FWD, false, config.nra_ODE_fwd_timeout));
ode_gsl_ctcs.push_back(nl_ctc2);
}
} else {
for (auto const & ode_ctr : ode_ctrs) {
// Add Forward ODE Pruning (Underapproximation, using GNU GSL)
ode_gsl_ctcs.push_back(mk_contractor_gsl(box, ode_ctr, eval_ctc, ode_direction::FWD, use_cache, config.nra_ODE_fwd_timeout));
ode_gsl_ctcs.push_back(nl_ctc);
}
}
}
// 2.6. Build ODE Contractors (using CAPD4)
vector<contractor> ode_capd4_fwd_ctcs;
vector<contractor> ode_capd4_bwd_ctcs;
for (auto const & ode_ctr : ode_ctrs) {
// 2.6.1. Add Forward ODE Pruning (Overapproximation, using CAPD4)
if (config.nra_ODE_cache) {
ode_capd4_fwd_ctcs.emplace_back(
mk_contractor_cache(
mk_contractor_try(
mk_contractor_seq(mk_contractor_capd_full(box, ode_ctr, ode_direction::FWD, config.nra_ODE_taylor_order, config.nra_ODE_grid_size, use_cache, config.nra_ODE_fwd_timeout),
nl_ctc))));
} else {
ode_capd4_fwd_ctcs.emplace_back(
mk_contractor_try(
mk_contractor_seq(
mk_contractor_capd_full(box, ode_ctr, ode_direction::FWD, config.nra_ODE_taylor_order, config.nra_ODE_grid_size, use_cache, config.nra_ODE_fwd_timeout),
nl_ctc)));
}
}
if (!config.nra_ODE_forward_only) {
// 2.6.2. Add Backward ODE Pruning (Overapproximation, using CAPD4)
for (auto const & ode_ctr : ode_ctrs_rev) {
if (config.nra_ODE_cache) {
ode_capd4_bwd_ctcs.emplace_back(
mk_contractor_cache(
mk_contractor_try(
mk_contractor_seq(
mk_contractor_capd_full(box, ode_ctr, ode_direction::BWD, config.nra_ODE_taylor_order, config.nra_ODE_grid_size, use_cache, config.nra_ODE_bwd_timeout),
nl_ctc))));
} else {
ode_capd4_bwd_ctcs.emplace_back(
mk_contractor_try(
mk_contractor_seq(
mk_contractor_capd_full(box, ode_ctr, ode_direction::BWD, config.nra_ODE_taylor_order, config.nra_ODE_grid_size, use_cache, config.nra_ODE_bwd_timeout),
nl_ctc)));
}
}
}
if (config.nra_ODE_sampling) {
if (config.nra_parallel) {
ctcs.push_back(mk_contractor_parallel_any(
mk_contractor_try_or(mk_contractor_throw_if_empty(mk_contractor_seq(ode_gsl_ctcs)),
mk_contractor_empty()),
mk_contractor_seq(mk_contractor_seq(ode_capd4_fwd_ctcs),
mk_contractor_seq(ode_capd4_bwd_ctcs))));
} else {
ctcs.push_back(
mk_contractor_try_or(
// Try Underapproximation(GSL) if it fails try Overapproximation(CAPD4)
mk_contractor_throw_if_empty(mk_contractor_seq(ode_gsl_ctcs)),
mk_contractor_seq(mk_contractor_seq(ode_capd4_fwd_ctcs),
mk_contractor_seq(ode_capd4_bwd_ctcs))));
}
} else {
ctcs.insert(ctcs.end(), ode_capd4_fwd_ctcs.begin(), ode_capd4_fwd_ctcs.end());
ctcs.insert(ctcs.end(), ode_capd4_bwd_ctcs.begin(), ode_capd4_bwd_ctcs.end());
}
}
if (complete) {
// 2.7 Build Eval contractors
vector<contractor> eval_ctcs;
for (auto const & nl_ctr : nl_ctrs) {
eval_ctcs.push_back(mk_contractor_eval(nl_ctr, use_cache));
}
return mk_contractor_seq(mk_contractor_fixpoint(default_strategy::term_cond, ctcs),
mk_contractor_seq(eval_ctcs));
} else {
return mk_contractor_fixpoint(default_strategy::term_cond, ctcs);
}
}
box ncbt_icp::solve(box b, contractor & ctc, SMTConfig & config) {
thread_local static unordered_set<shared_ptr<constraint>> used_constraints;
used_constraints.clear();
static unsigned prune_count = 0;
thread_local static vector<box> box_stack;
box_stack.clear();
box_stack.push_back(b);
do {
// Loop Invariant
DREAL_LOG_INFO << "ncbt_icp::solve - loop"
<< "\t" << "box stack Size = " << box_stack.size();
b = box_stack.back();
try {
ctc.prune(b, config);
auto const this_used_constraints = ctc.used_constraints();
used_constraints.insert(this_used_constraints.begin(), this_used_constraints.end());
if (config.nra_use_stat) { config.nra_stat.increase_prune(); }
} catch (contractor_exception & e) {
// Do nothing
}
prune_count++;
box_stack.pop_back();
if (!b.is_empty()) {
// SAT
tuple<int, box, box> splits = b.bisect(config.nra_precision);
if (config.nra_use_stat) { config.nra_stat.increase_branch(); }
int const index = get<0>(splits);
if (index >= 0) {
box const & first = get<1>(splits);
box const & second = get<2>(splits);
assert(first.get_idx_last_branched() == index);
assert(second.get_idx_last_branched() == index);
if (second.is_bisectable()) {
box_stack.push_back(second);
box_stack.push_back(first);
} else {
box_stack.push_back(first);
box_stack.push_back(second);
}
} else {
break;
}
} else {
// UNSAT (b is emptified by pruning operators)
// If this bisect_var is not used in all used
// constraints, this box is safe to be popped.
thread_local static unordered_set<Enode *> used_vars;
used_vars.clear();
for (auto used_ctr : used_constraints) {
auto this_used_vars = used_ctr->get_vars();
used_vars.insert(this_used_vars.begin(), this_used_vars.end());
}
while (box_stack.size() > 0) {
int const bisect_var = box_stack.back().get_idx_last_branched();
assert(bisect_var >= 0);
// If this bisect_var is not used in all used
// constraints, this box is safe to be popped.
if (used_vars.find(b.get_vars()[bisect_var]) != used_vars.end()) {
// DREAL_LOG_FATAL << b.get_vars()[bisect_var] << " is used in "
// << *used_ctr << " and it's not safe to skip";
break;
}
// DREAL_LOG_FATAL << b.get_vars()[bisect_var] << " is not used and it's safe to skip this box"
// << " (" << box_stack.size() << ")";
box_stack.pop_back();
}
}
} while (box_stack.size() > 0);
DREAL_LOG_DEBUG << "prune count = " << prune_count;
ctc.set_used_constraints(used_constraints);
return b;
}
void contractor_generic_forall::handle_disjunction(box & b, vector<Enode *> const &vec, bool const p, SMTConfig & config) {
DREAL_LOG_DEBUG << "contractor_generic_forall::handle_disjunction" << endl;
unordered_set<Enode *> forall_vars;
for (Enode * e : vec) {
std::unordered_set<Enode *> const & vars = e->get_forall_vars();
forall_vars.insert(vars.begin(), vars.end());
}
unordered_map<Enode*, ibex::Interval> subst;
if (!forall_vars.empty()) {
// Step 2. Find a counter-example
// Solve(¬ l_1 ∧ ¬ l_2 ∧ ... ∧ ¬ l_n)
//
// Make each ¬ l_i as a contractor ctc_i
// Make a fixed_point contractor with ctc_is.
// Pass it to icp::solve
box counterexample = find_CE(b, forall_vars, vec, p, config);
if (counterexample.is_empty()) {
// Step 2.1. (NO Counterexample)
// Return B.
DREAL_LOG_DEBUG << "handle_disjunction: no counterexample found." << endl
<< "current box = " << endl
<< b << endl;
return;
} else {
// Step 2.2. (There IS a counterexample C)
//
// Using C, prune B.
//
// We've found a counterexample (c1, c2) where ¬ f(c1, c2) holds
// Prune X using a point 'y = c2'. (technically, a point in c2, which is an interval)
subst = make_subst_from_value(counterexample, forall_vars);
}
}
// Step 3. Compute B_i = prune(B, l_i)
// Update B with ∨ B_i
// i
thread_local static vector<box> boxes;
boxes.clear();
auto vars = b.get_vars();
unordered_set<Enode*> const var_set(vars.begin(), vars.end());
for (Enode * e : vec) {
if (!e->get_exist_vars().empty()) {
lbool polarity = p ? l_True : l_False;
if (e->isNot()) {
polarity = !polarity;
e = e->get1st();
}
auto ctr = make_shared<nonlinear_constraint>(e, var_set, polarity, subst);
if (ctr->get_var_array().size() == 0) {
auto result = ctr->eval(b);
if (result.first != false) {
boxes.emplace_back(b);
}
} else {
contractor ctc = mk_contractor_ibex_fwdbwd(ctr);
box bt(b);
ctc.prune(bt, config);
m_output.union_with(ctc.output());
unordered_set<shared_ptr<constraint>> const & used_ctrs = ctc.used_constraints();
m_used_constraints.insert(used_ctrs.begin(), used_ctrs.end());
boxes.emplace_back(bt);
}
}
}
b = hull(boxes);
return;
}
