PreprocessingPassResult SygusAbduct::applyInternal(
AssertionPipeline* assertionsToPreprocess)
{
NodeManager* nm = NodeManager::currentNM();
Trace("sygus-abduct") << "Run sygus abduct..." << std::endl;
Trace("sygus-abduct-debug") << "Collect symbols..." << std::endl;
std::unordered_set<Node, NodeHashFunction> symset;
std::vector<Node>& asserts = assertionsToPreprocess->ref();
// do we have any assumptions, e.g. via check-sat-assuming?
bool usingAssumptions = (assertionsToPreprocess->getNumAssumptions() > 0);
// The following is our set of "axioms". We construct this set only when the
// usingAssumptions (above) is true. In this case, our input formula is
// partitioned into Fa ^ Fc as described in the header of this class, where:
// - The conjunction of assertions marked as assumptions are the negated
// conjecture Fc, and
// - The conjunction of all other assertions are the axioms Fa.
std::vector<Node> axioms;
for (size_t i = 0, size = asserts.size(); i < size; i++)
{
expr::getSymbols(asserts[i], symset);
// if we are not an assumption, add it to the set of axioms
if (usingAssumptions && i < assertionsToPreprocess->getAssumptionsStart())
{
axioms.push_back(asserts[i]);
}
}
Trace("sygus-abduct-debug")
<< "...finish, got " << symset.size() << " symbols." << std::endl;
Trace("sygus-abduct-debug") << "Setup symbols..." << std::endl;
std::vector<Node> syms;
std::vector<Node> vars;
std::vector<Node> varlist;
std::vector<TypeNode> varlistTypes;
for (const Node& s : symset)
{
TypeNode tn = s.getType();
if (tn.isFirstClass())
{
std::stringstream ss;
ss << s;
Node var = nm->mkBoundVar(tn);
syms.push_back(s);
vars.push_back(var);
Node vlv = nm->mkBoundVar(ss.str(), tn);
varlist.push_back(vlv);
varlistTypes.push_back(tn);
}
}
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make abduction predicate..." << std::endl;
// make the abduction predicate to synthesize
TypeNode abdType = varlistTypes.empty() ? nm->booleanType()
: nm->mkPredicateType(varlistTypes);
Node abd = nm->mkBoundVar("A", abdType);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make abduction predicate app..." << std::endl;
std::vector<Node> achildren;
achildren.push_back(abd);
achildren.insert(achildren.end(), vars.begin(), vars.end());
Node abdApp = vars.empty() ? abd : nm->mkNode(APPLY_UF, achildren);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Set attributes..." << std::endl;
// set the sygus bound variable list
Node abvl = nm->mkNode(BOUND_VAR_LIST, varlist);
abd.setAttribute(theory::SygusSynthFunVarListAttribute(), abvl);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make conjecture body..." << std::endl;
Node input = asserts.size() == 1 ? asserts[0] : nm->mkNode(AND, asserts);
input = input.substitute(syms.begin(), syms.end(), vars.begin(), vars.end());
// A(x) => ~input( x )
input = nm->mkNode(OR, abdApp.negate(), input.negate());
Trace("sygus-abduct-debug") << "...finish" << std::endl;
Trace("sygus-abduct-debug") << "Make conjecture..." << std::endl;
Node res = input.negate();
if (!vars.empty())
{
Node bvl = nm->mkNode(BOUND_VAR_LIST, vars);
// exists x. ~( A( x ) => ~input( x ) )
res = nm->mkNode(EXISTS, bvl, res);
}
// sygus attribute
Node sygusVar = nm->mkSkolem("sygus", nm->booleanType());
theory::SygusAttribute ca;
sygusVar.setAttribute(ca, true);
Node instAttr = nm->mkNode(INST_ATTRIBUTE, sygusVar);
std::vector<Node> iplc;
iplc.push_back(instAttr);
if (!axioms.empty())
{
Node aconj = axioms.size() == 1 ? axioms[0] : nm->mkNode(AND, axioms);
aconj =
aconj.substitute(syms.begin(), syms.end(), vars.begin(), vars.end());
Trace("sygus-abduct") << "---> Assumptions: " << aconj << std::endl;
Node sc = nm->mkNode(AND, aconj, abdApp);
Node vbvl = nm->mkNode(BOUND_VAR_LIST, vars);
sc = nm->mkNode(EXISTS, vbvl, sc);
Node sygusScVar = nm->mkSkolem("sygus_sc", nm->booleanType());
sygusScVar.setAttribute(theory::SygusSideConditionAttribute(), sc);
instAttr = nm->mkNode(INST_ATTRIBUTE, sygusScVar);
// build in the side condition
// exists x. A( x ) ^ input_axioms( x )
// as an additional annotation on the sygus conjecture. In other words,
// the abducts A we procedure must be consistent with our axioms.
iplc.push_back(instAttr);
}
Node instAttrList = nm->mkNode(INST_PATTERN_LIST, iplc);
Node fbvl = nm->mkNode(BOUND_VAR_LIST, abd);
// forall A. exists x. ~( A( x ) => ~input( x ) )
res = nm->mkNode(FORALL, fbvl, res, instAttrList);
Trace("sygus-abduct-debug") << "...finish" << std::endl;
res = theory::Rewriter::rewrite(res);
Trace("sygus-abduct") << "Generate: " << res << std::endl;
Node trueNode = nm->mkConst(true);
assertionsToPreprocess->replace(0, res);
for (size_t i = 1, size = assertionsToPreprocess->size(); i < size; ++i)
{
assertionsToPreprocess->replace(i, trueNode);
}
return PreprocessingPassResult::NO_CONFLICT;
}
