mirrors/z3
3
0
Fork 0
mirror of https://github.com/Z3Prover/z3 synced 2025-04-06 09:34:08 +00:00
Code Activity

na

Browse source 
Signed-off-by: Nikolaj Bjorner <nbjorner@microsoft.com>
This commit is contained in:
Nikolaj Bjorner 2020-05-05 09:51:28 -07:00
parent a34c5a9450
commit 3985943eec
3 changed files with 38 additions and 167 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
src/smt/smt_context.cpp
View file

@ -1601,7 +1601,7 @@ namespace smt {
if (inconsistent())
return false;
}
#if 0
#if 1
if (at_search_level() && induction::should_try(*this)) {
get_induction()();
}

173
src/smt/smt_induction.cpp
View file

@ -158,7 +158,7 @@ enode_vector induction_lemmas::induction_positions(enode* n) {
for (unsigned i = 0; i < todo.size(); ++i) {
n = todo[i];
for (enode* a : smt::enode::args(n)) {
add_todo(a);
add_todo(a);
if (!a->is_marked2() && viable_induction_term(n, a)) {
result.push_back(a);
a->set_mark2();
@ -171,86 +171,7 @@ enode_vector induction_lemmas::induction_positions(enode* n) {
n->unset_mark2();
return result;
}
void induction_lemmas::abstract1(enode* n, enode* t, expr* x, abstractions& result) {
expr_safe_replace rep(m);
rep.insert(t->get_owner(), x);
expr_ref e(n->get_owner(), m);
rep(e);
result.push_back(abstraction(e));
}
/**
* abstraction candidates for replacing different occurrence of t in n by x
* it returns all possible non-empty subsets of t replaced by x.
*
* TBD: add term sharing throttle.
* TDD: add depth throttle.
*/
void induction_lemmas::abstract(enode* n, enode* t, expr* x, abstractions& result) {
std::cout << "abs: " << result.size() << ": " << mk_pp(n->get_owner(), m) << "\n";
if (n->get_root() == t->get_root()) {
result.push_back(abstraction(m, x, n->get_owner(), t->get_owner()));
return;
}
func_decl* f = n->get_owner()->get_decl();
// check if n is a s
if (f->is_skolem()) {
expr_ref e(n->get_owner(), m);
result.push_back(abstraction(e));
}
abstraction_args r1, r2;
r1.push_back(abstraction_arg(m));
for (enode* arg : enode::args(n)) {
unsigned n = result.size();
abstract(arg, t, x, result);
std::cout << result.size() << "\n";
for (unsigned i = n; i < result.size(); ++i) {
abstraction& a = result[i];
for (auto const& v : r1) {
r2.push_back(v);
r2.back().push_back(a);
}
}
r1.swap(r2);
r2.reset();
result.shrink(n);
}
for (auto const& a : r1) {
result.push_back(abstraction(m, m.mk_app(n->get_decl(), a.m_terms), a.m_eqs));
}
};
/**
* filter generalizations based on value_generator
* If all evaluations are counter-examples, include
* candidate generalization.
*/
void induction_lemmas::filter_abstractions(bool sign, abstractions& abs) {
vector<expr_ref_vector> values;
expr_ref_vector fmls(m);
for (auto & a : abs) fmls.push_back(a.m_term);
std::cout << "sweep\n";
vs(fmls, values);
std::cout << "done sweep\n";
unsigned j = 0;
for (unsigned i = 0; i < fmls.size(); ++i) {
bool all_cex = true;
for (auto const& vec : values) {
if (vec[i] && (m.is_true(vec[i]) == sign))
continue;
all_cex = false;
break;
}
if (all_cex) {
abs[j++] = abs.get(i);
}
}
std::cout << "resulting size: " << j << " down from " << abs.size() << "\n";
abs.shrink(j);
}
/**
extract substitutions for x into accessor values of the same sort.
collect side-conditions for the accessors to be well defined.
@ -308,35 +229,21 @@ void induction_lemmas::mk_hypothesis_substs_rec(unsigned depth, sort* s, expr* y
*/
void induction_lemmas::mk_hypothesis_lemma(expr_ref_vector const& conds, expr_pair_vector const& subst, literal alpha) {
expr* alpha_e = ctx.bool_var2expr(alpha.var());
expr_ref beta(alpha_e, m);
expr_ref beta(m);
ctx.literal2expr(alpha, beta);
expr_safe_replace rep(m);
for (auto const& p : subst) {
rep.insert(p.first, p.second);
}
rep(beta); // set beta := alpha[sk/acc(acc2(sk))]
literal b_lit = mk_literal(beta);
if (alpha.sign()) b_lit.neg();
// alpha & is-c(sk) => ~alpha[sk/acc(sk)]
literal_vector lits;
lits.push_back(~alpha);
for (expr* c : conds) lits.push_back(~mk_literal(c));
lits.push_back(b_lit);
lits.push_back(~mk_literal(beta));
add_th_lemma(lits);
}
void induction_lemmas::create_hypotheses(unsigned depth, expr* sk, literal alpha) {
expr_ref_vector conds(m);
cond_substs_t subst;
expr* alpha_e = ctx.bool_var2expr(alpha.var());
mk_hypothesis_substs(depth, sk, subst);
for (auto& p : subst) {
expr_pair_vector vec;
vec.push_back(std::make_pair(sk, p.second));
mk_hypothesis_lemma(p.first, vec, alpha);
}
}
#if 0
void induction_lemmas::create_hypotheses(unsigned depth, expr_ref_vector const& sks, literal alpha) {
if (sks.empty())
return;
@ -350,55 +257,33 @@ void induction_lemmas::create_hypotheses(unsigned depth, expr_ref_vector const&
// append the identity substitution:
expr_ref_vector conds(m);
subst.push_back(std::make_pair(conds, expr_ref(sk, m)));
substs.push_back(std::make_pair(sk, subst));
}
// create cross-product of instantiations:
vector<std::pair<expr_ref_vector, expr_pair_vector>> s1, s2;
si.push_back(std::make_pair(expr_ref_vector(m), expr_pair_vector()));
s1.push_back(std::make_pair(expr_ref_vector(m), expr_pair_vector()));
for (auto const& x2cond_sub : substs) {
s2.reset();
for (auto const& cond_sub : x2cond_sub.second) {
s2.reset();
for (auto const& cond_subs : s1) {
expr_pair_vector pairs(cond_subs.second);
expr_ref_vector conds(cond_subs.first);
pairs.push_back(x2cond_sub.first, cond_sub.second);
pairs.push_back(std::make_pair(x2cond_sub.first, cond_sub.second));
conds.append(cond_sub.first);
s2.push_back(std::make_pair(conds, pairs));
}
s1.swap(s2);
}
s1.swap(s2);
}
s1.pop_back(); // last substitution is the identity.
s1.pop_back(); // last substitution is the identity
// extract lemmas from instantiations
for (auto& p : s1) {
mk_hypothesis_lemam(p.first, p.second, alpha);
mk_hypothesis_lemma(p.first, p.second, alpha);
}
}
#endif
void induction_lemmas::create_lemmas(expr* sk, abstraction& a, literal lit) {
std::cout << "abstraction: " << a.m_term << "\n";
sort* s = m.get_sort(sk);
if (!m_dt.is_datatype(s))
return;
expr_ref alpha = a.m_term;
literal alpha_lit = mk_literal(alpha);
if (lit.sign()) alpha_lit.neg();
create_hypotheses(1, sk, alpha_lit);
literal_vector lits;
// phi & eqs => alpha
lits.push_back(~lit);
for (auto const& p : a.m_eqs) {
lits.push_back(~mk_literal(m.mk_eq(p.first, p.second)));
}
lits.push_back(alpha_lit);
add_th_lemma(lits);
}
void induction_lemmas::add_th_lemma(literal_vector const& lits) {
IF_VERBOSE(0, ctx.display_literals_verbose(verbose_stream() << "lemma:\n", lits) << "\n");
@ -420,21 +305,35 @@ literal induction_lemmas::mk_literal(expr* e) {
bool induction_lemmas::operator()(literal lit) {
unsigned num = m_num_lemmas;
enode* r = ctx.bool_var2enode(lit.var());
unsigned position = 0;
expr_ref_vector sks(m);
expr_safe_replace rep(m);
// have to be non-overlapping:
for (enode* n : induction_positions(r)) {
expr* t = n->get_owner();
sort* s = m.get_sort(t);
expr_ref sk(m.mk_fresh_const("sk", s), m);
std::cout << "abstract " << mk_pp(t, m) << " " << sk << "\n";
abstractions abs;
abstract1(r, n, sk, abs);
if (abs.size() > 1) filter_abstractions(lit.sign(), abs);
for (abstraction& a : abs) {
create_lemmas(sk, a, lit);
if (is_uninterp_const(t)) { // for now, to avoid overlapping terms
sort* s = m.get_sort(t);
expr_ref sk(m.mk_fresh_const("sk", s), m);
sks.push_back(sk);
rep.insert(t, sk);
}
++position;
}
return m_num_lemmas > num;
expr_ref alpha(m);
ctx.literal2expr(lit, alpha);
rep(alpha);
literal alpha_lit = mk_literal(alpha);
// alpha is the minimal instance of induction_positions where lit holds
// alpha & is-c(sk) => ~alpha[sk/acc(sk)]
create_hypotheses(1, sks, alpha_lit);
if (m_num_lemmas == num)
return false;
// lit => alpha
literal_vector lits;
lits.push_back(~lit);
lits.push_back(alpha_lit);
add_th_lemma(lits);
return true;
}
induction_lemmas::induction_lemmas(context& ctx, ast_manager& m, value_sweep& vs):

30
src/smt/smt_induction.h
View file

@ -58,30 +58,6 @@ namespace smt {
unsigned m_num_lemmas;
typedef svector<std::pair<expr*,expr*>> expr_pair_vector;
struct abstraction {
expr_ref m_term;
expr_pair_vector m_eqs;
abstraction(expr_ref& e): m_term(e) {}
abstraction(ast_manager& m, expr* e, expr* n1, expr* n2): m_term(e, m) {
if (n1 != n2) m_eqs.push_back(std::make_pair(n1, n2));
}
abstraction(ast_manager& m, expr* e, expr_pair_vector const& eqs):
m_term(e, m), m_eqs(eqs) {
}
};
typedef vector<abstraction> abstractions;
struct abstraction_arg {
expr_ref_vector m_terms;
expr_pair_vector m_eqs;
abstraction_arg(ast_manager& m): m_terms(m) {}
void push_back(abstraction& a) {
m_terms.push_back(a.m_term);
m_eqs.append(a.m_eqs);
}
};
typedef vector<abstraction_arg> abstraction_args;
typedef std::pair<expr_ref_vector, expr_ref> cond_subst_t;
typedef vector<cond_subst_t> cond_substs_t;
@ -90,14 +66,10 @@ namespace smt {
bool viable_induction_children(enode* n);
bool viable_induction_term(enode* p , enode* n);
enode_vector induction_positions(enode* n);
void abstract(enode* n, enode* t, expr* x, abstractions& result);
void abstract1(enode* n, enode* t, expr* x, abstractions& result);
void filter_abstractions(bool sign, abstractions& abs);
void create_lemmas(expr* sk, abstraction& a, literal lit);
void mk_hypothesis_substs(unsigned depth, expr* x, cond_substs_t& subst);
void mk_hypothesis_substs_rec(unsigned depth, sort* s, expr* y, expr_ref_vector& conds, cond_substs_t& subst);
void mk_hypothesis_lemma(expr_ref_vector const& conds, expr_pair_vector const& subst, literal alpha);
void create_hypotheses(unsigned depth, expr* sk, literal alpha);
void create_hypotheses(unsigned depth, expr_ref_vector const& sks, literal alpha);
literal mk_literal(expr* e);
void add_th_lemma(literal_vector const& lits);