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feat(library/blast/congruence_closure): add support for propagating units in the congruence closure module

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See blast_cc12.lean for example.
This commit is contained in:
Leonardo de Moura 2015-11-22 15:39:44 -08:00
parent f326e731a0
commit 94f7b7f95d
3 changed files with 125 additions and 38 deletions
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127
src/library/blast/congruence_closure.cpp
View file

@ -105,11 +105,11 @@ scope_congruence_closure::~scope_congruence_closure() {
}
void congruence_closure::initialize() {
mk_entry_core(get_iff_name(), mk_true());
mk_entry_core(get_iff_name(), mk_false());
mk_entry_core(get_iff_name(), mk_true(), false);
mk_entry_core(get_iff_name(), mk_false(), false);
}
void congruence_closure::mk_entry_core(name const & R, expr const & e) {
void congruence_closure::mk_entry_core(name const & R, expr const & e, bool to_propagate) {
lean_assert(!m_entries.find(eqc_key(R, e)));
entry n;
n.m_next = e;
@ -117,6 +117,7 @@ void congruence_closure::mk_entry_core(name const & R, expr const & e) {
n.m_cg_root = e;
n.m_size = 1;
n.m_flipped = false;
n.m_to_propagate = to_propagate;
m_entries.insert(eqc_key(R, e), n);
if (R != get_eq_name()) {
// lift equalities to R
@ -137,10 +138,18 @@ void congruence_closure::mk_entry_core(name const & R, expr const & e) {
}
}
void congruence_closure::mk_entry(name const & R, expr const & e) {
if (m_entries.find(eqc_key(R, e)))
void congruence_closure::mk_entry(name const & R, expr const & e, bool to_propagate) {
if (to_propagate && !is_prop(e))
to_propagate = false;
if (auto it = m_entries.find(eqc_key(R, e))) {
if (!it->m_to_propagate && to_propagate) {
entry new_it = *it;
new_it.m_to_propagate = to_propagate;
m_entries.insert(eqc_key(R, e), new_it);
}
return;
mk_entry_core(R, e);
}
mk_entry_core(R, e, to_propagate);
}
static bool all_distinct(buffer<expr> const & es) {
@ -539,7 +548,19 @@ void congruence_closure::add_congruence_table(ext_congr_lemma const & lemma, exp
check_iff_true(k);
}
void congruence_closure::internalize_core(name const & R, expr const & e) {
static bool is_logical_app(expr const & n) {
if (!is_app(n)) return false;
expr const & fn = get_app_fn(n);
return
is_constant(fn) &&
(const_name(fn) == get_or_name() ||
const_name(fn) == get_and_name() ||
const_name(fn) == get_not_name() ||
const_name(fn) == get_iff_name() ||
(const_name(fn) == get_ite_name() && is_prop(n)));
}
void congruence_closure::internalize_core(name const & R, expr const & e, bool toplevel, bool to_propagate) {
lean_assert(closed(e));
if (has_expr_metavar(e))
return;
@ -552,40 +573,53 @@ void congruence_closure::internalize_core(name const & R, expr const & e) {
case expr_kind::Sort:
return;
case expr_kind::Constant: case expr_kind::Local:
mk_entry_core(R, e, to_propagate);
return;
case expr_kind::Lambda:
mk_entry_core(R, e);
mk_entry_core(R, e, false);
return;
case expr_kind::Macro:
for (unsigned i = 0; i < macro_num_args(e); i++)
internalize_core(R, macro_arg(e, i));
mk_entry_core(R, e);
internalize_core(R, macro_arg(e, i), false, false);
mk_entry_core(R, e, to_propagate);
break;
case expr_kind::Pi:
// TODO(Leo): should we support congruence for arrows?
if (is_arrow(e) && is_prop(binding_domain(e)) && is_prop(binding_body(e))) {
internalize_core(R, binding_domain(e));
internalize_core(R, binding_body(e));
to_propagate = toplevel; // we must propagate children if arrow is top-level
internalize_core(R, binding_domain(e), toplevel, to_propagate);
internalize_core(R, binding_body(e), toplevel, to_propagate);
}
if (is_prop(e)) {
mk_entry_core(R, e);
mk_entry_core(R, e, false);
}
return;
case expr_kind::App: {
mk_entry_core(R, e);
bool is_lapp = is_logical_app(e);
mk_entry_core(R, e, to_propagate && !is_lapp);
buffer<expr> args;
expr const & fn = get_app_args(e, args);
if (toplevel) {
if (is_lapp) {
to_propagate = true; // we must propagate the children of a top-level logical app (or, and, iff, ite)
} else {
toplevel = false; // children of a non-logical application will not be marked as toplevel
}
} else {
to_propagate = false;
}
if (auto lemma = mk_ext_congr_lemma(R, fn, args.size())) {
list<optional<name>> const * it = &(lemma->m_rel_names);
for (expr const & arg : args) {
lean_assert(*it);
if (auto R1 = head(*it)) {
internalize_core(*R1, arg);
internalize_core(*R1, arg, toplevel, to_propagate);
add_occurrence(R, e, *R1, arg);
}
it = &tail(*it);
}
if (!lemma->m_fixed_fun) {
internalize_core(get_eq_name(), fn);
internalize_core(get_eq_name(), fn, false, false);
add_occurrence(get_eq_name(), e, get_eq_name(), fn);
}
add_congruence_table(*lemma, e);
@ -594,17 +628,18 @@ void congruence_closure::internalize_core(name const & R, expr const & e) {
}}
}
void congruence_closure::internalize(name const & R, expr const & e) {
void congruence_closure::internalize(name const & R, expr const & e, bool toplevel) {
flet<congruence_closure *> set_cc(g_cc, this);
internalize_core(R, e);
bool to_propagate = false; // We don't need to mark units for propagation
internalize_core(R, e, toplevel, to_propagate);
process_todo();
}
void congruence_closure::internalize(expr const & e) {
if (is_prop(e))
internalize(get_iff_name(), e);
internalize(get_iff_name(), e, true);
else
internalize(get_eq_name(), e);
internalize(get_eq_name(), e, false);
}
/*
@ -663,6 +698,10 @@ void congruence_closure::reinsert_parents(name const & R, expr const & e) {
});
}
static bool is_interpreted(expr const & e) {
return is_constant(e, get_true_name()) || is_constant(e, get_false_name());
}
void congruence_closure::add_eqv_step(name const & R, expr e1, expr e2, expr const & H) {
auto n1 = m_entries.find(eqc_key(R, e1));
auto n2 = m_entries.find(eqc_key(R, e2));
@ -677,7 +716,15 @@ void congruence_closure::add_eqv_step(name const & R, expr e1, expr e2, expr con
// We want r2 to be the root of the combined class.
if (r1->m_size > r2->m_size) {
// We swap (e1,n1,r1) with (e2,n2,r2) when
// 1- is_interpreted(n1->m_root) && !is_interpreted(n2->m_root).
// Reason: to decide when to propagate we check whether the root of the equivalence class
// is true/false. So, this condition is to make sure if true/false is an equivalence class,
// then one of them is the root. If both are, it doesn't matter, since the state is inconsistent
// anyway.
// 2- r1->m_size > r2->m_size
// Reason: performance. Condition was has precedence
if ((r1->m_size > r2->m_size && !is_interpreted(n2->m_root)) || is_interpreted(n1->m_root)) {
std::swap(e1, e2);
std::swap(n1, n2);
std::swap(r1, r2);
@ -704,9 +751,13 @@ void congruence_closure::add_eqv_step(name const & R, expr e1, expr e2, expr con
remove_parents(R, e1);
// force all m_root fields in e1 equivalence class to point to e2_root
bool propagate = R == get_iff_name() && is_interpreted(e2_root);
buffer<expr> to_propagate;
expr it = e1;
do {
auto it_n = m_entries.find(eqc_key(R, it));
if (propagate && it_n->m_to_propagate)
to_propagate.push_back(it);
lean_assert(it_n);
entry new_it_n = *it_n;
new_it_n.m_root = e2_root;
@ -750,12 +801,31 @@ void congruence_closure::add_eqv_step(name const & R, expr e1, expr e2, expr con
for (name const & R2 : m_non_eq_relations) {
if (m_entries.find(eqc_key(R2, e1)) ||
m_entries.find(eqc_key(R2, e2))) {
mk_entry(R2, e1);
mk_entry(R2, e2);
mk_entry(R2, e1, false);
mk_entry(R2, e2, false);
push_todo(R2, e1, e2, *g_lift_mark);
}
}
}
// propagate new hypotheses back to current state
if (!to_propagate.empty()) {
state & s = curr_state();
app_builder & b = get_app_builder();
bool is_true = e2_root == mk_true();
for (expr const & e : to_propagate) {
lean_assert(R == get_iff_name());
expr type = e;
expr pr = *get_eqv_proof(R, e, e2_root);
if (is_true) {
pr = b.mk_of_iff_true(pr);
} else {
type = b.mk_not(e);
pr = b.mk_not_of_iff_false(pr);
}
s.mk_hypothesis(type, pr);
}
}
}
void congruence_closure::process_todo() {
@ -790,15 +860,18 @@ void congruence_closure::add(hypothesis_idx hidx) {
name R; expr lhs, rhs;
if (is_relation_app(p, R, lhs, rhs)) {
if (is_neg) {
internalize_core(get_iff_name(), p);
bool toplevel = true; bool to_propagate = false;
internalize_core(get_iff_name(), p, toplevel, to_propagate);
add_eqv(get_iff_name(), p, mk_false(), b.mk_iff_false_intro(h.get_self()));
} else {
internalize_core(R, lhs);
internalize_core(R, rhs);
bool toplevel = false; bool to_propagate = false;
internalize_core(R, lhs, toplevel, to_propagate);
internalize_core(R, rhs, toplevel, to_propagate);
add_eqv(R, lhs, rhs, h.get_self());
}
} else if (is_prop(p)) {
internalize_core(get_iff_name(), p);
bool toplevel = true; bool to_propagate = false;
internalize_core(get_iff_name(), p, toplevel, to_propagate);
if (is_neg) {
add_eqv(get_iff_name(), p, mk_false(), b.mk_iff_false_intro(h.get_self()));
} else {

12
src/library/blast/congruence_closure.h
View file

@ -43,7 +43,8 @@ class congruence_closure {
// store 'target' at 'm_target', and 'H' at 'm_proof'. Both fields are none if 'e' == m_root
optional<expr> m_target;
optional<expr> m_proof;
bool m_flipped; // proof has been flipped
unsigned m_flipped:1; // proof has been flipped
unsigned m_to_propagate:1; // must be propagated back to state when in equivalence class containing true/false
unsigned m_size; // number of elements in the equivalence class, it is meaningless if 'e' != m_root
};
@ -101,7 +102,8 @@ class congruence_closure {
void update_non_eq_relations(name const & R);
void internalize_core(name const & R, expr const & e);
void register_to_propagate(expr const & e);
void internalize_core(name const & R, expr const & e, bool toplevel, bool to_propagate);
void process_todo();
int compare_symm(name const & R, expr lhs1, expr rhs1, expr lhs2, expr rhs2) const;
@ -110,8 +112,8 @@ class congruence_closure {
congr_key mk_congr_key(ext_congr_lemma const & lemma, expr const & e) const;
void check_iff_true(congr_key const & k);
void mk_entry_core(name const & R, expr const & e);
void mk_entry(name const & R, expr const & e);
void mk_entry_core(name const & R, expr const & e, bool to_propagate);
void mk_entry(name const & R, expr const & e, bool to_propagate);
void add_occurrence(name const & Rp, expr const & parent, name const & Rc, expr const & child);
void add_congruence_table(ext_congr_lemma const & lemma, expr const & e);
void invert_trans(name const & R, expr const & e, optional<expr> new_target, optional<expr> new_proof);
@ -142,7 +144,7 @@ public:
4- Terms containing meta-variables.
5- The subterms of lambda-expressions.
6- Sorts (Type and Prop). */
void internalize(name const & R, expr const & e);
void internalize(name const & R, expr const & e, bool toplevel = false);
void internalize(expr const & e);
/** \brief Given a hypothesis H, this method will do the following based on the type of H

12
tests/lean/run/blast_cc12.lean Normal file
View file

@ -0,0 +1,12 @@
set_option blast.subst false
set_option blast.simp false
definition foo1 (a b : nat) (p : Prop) : a = b → (b = a → p) → p :=
by blast
print foo1
definition foo2 (a b c : nat) (p : Prop) : a = b → b = c → (c = a → p) → p :=
by blast
print foo2