box find_CE_via_underapprox(box const & b, unordered_set<Enode*> const & forall_vars, vector<Enode*> const & vec, bool const p, SMTConfig & config) {
box counterexample(b, forall_vars);
if (config.nra_shrink_for_dop) {
counterexample = shrink_for_dop(counterexample);
}
auto vars = counterexample.get_vars();
unordered_set<Enode*> const var_set(vars.begin(), vars.end());
ibex::IntervalVector & iv = counterexample.get_values();
for (Enode * e : vec) {
lbool polarity = p ? l_False : l_True;
if (e->isNot()) {
e = e->get1st();
polarity = !polarity;
}
if (e->isOr() || e->isAnd()) {
break;
}
nonlinear_constraint ctr(e, var_set, polarity);
if (ctr.is_neq()) {
break;
}
auto numctr = ctr.get_numctr();
// Construct iv from box b
if (numctr->op == ibex::CmpOp::GT || numctr->op == ibex::CmpOp::GEQ) {
numctr->f.ibwd(ibex::Interval(0.0, POS_INFINITY), iv);
} else if (numctr->op == ibex::CmpOp::LT || numctr->op == ibex::CmpOp::LEQ) {
numctr->f.ibwd(ibex::Interval(NEG_INFINITY, 0.0), iv);
} else if (numctr->op == ibex::CmpOp::EQ) {
numctr->f.ibwd(ibex::Interval(0.0, 0.0), iv);
} else {
ostringstream ss;
ss << "find_CE_via_underapprox: unknown constraint type, " << *numctr;
throw runtime_error(ss.str());
}
if (iv.is_empty()) {
// stop when counterexample is already empty;
return counterexample;
}
}
if (!iv.is_empty()) {
iv = iv.mid();
}
return counterexample;
}
box find_CE_via_overapprox(box const & b, unordered_set<Enode*> const & forall_vars, vector<Enode*> const & vec, bool const p, SMTConfig & config) {
vector<contractor> ctcs;
box counterexample(b, forall_vars);
if (config.nra_shrink_for_dop) {
counterexample = shrink_for_dop(counterexample);
}
auto vars = counterexample.get_vars();
unordered_set<Enode *> var_set(vars.begin(), vars.end());
for (Enode * e : vec) {
lbool polarity = p ? l_False : l_True;
if (e->isNot()) {
polarity = !polarity;
e = e->get1st();
}
contractor ctc = make_contractor(e, polarity, counterexample, var_set);
ctcs.push_back(ctc);
}
contractor fp = mk_contractor_fixpoint(default_strategy::term_cond, ctcs);
random_icp icp(fp, config);
counterexample = icp.solve(counterexample, config.nra_precision);
return counterexample;
}