Fix performance problem in has_free_var. Add new test at src/tests/kernel/free_vars.cpp that exposes the problem.

Signed-off-by: Leonardo de Moura <leonardo@microsoft.com>
This commit is contained in:
Leonardo de Moura 2013-08-11 11:19:59 -07:00
parent 6d9a342f17
commit 4eeb72b0ee
2 changed files with 96 additions and 19 deletions

View file

@ -14,12 +14,7 @@ namespace lean {
/** \brief Functional object for checking whether a kernel expression has free variables or not. */ /** \brief Functional object for checking whether a kernel expression has free variables or not. */
class has_free_vars_fn { class has_free_vars_fn {
protected: protected:
expr_cell_offset_set m_visited; expr_cell_offset_set m_cached;
bool m_set_closed_flag;
virtual bool process_var(expr const & x, unsigned offset) {
return var_idx(x) >= offset;
}
bool apply(expr const & e, unsigned offset) { bool apply(expr const & e, unsigned offset) {
// handle easy cases // handle easy cases
@ -27,7 +22,7 @@ protected:
case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value: case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value:
return false; return false;
case expr_kind::Var: case expr_kind::Var:
return process_var(e, offset); return var_idx(e) >= offset;
case expr_kind::App: case expr_kind::Eq: case expr_kind::Lambda: case expr_kind::Pi: case expr_kind::Let: case expr_kind::App: case expr_kind::Eq: case expr_kind::Lambda: case expr_kind::Pi: case expr_kind::Let:
break; break;
} }
@ -35,11 +30,22 @@ protected:
if (e.raw()->is_closed()) if (e.raw()->is_closed())
return false; return false;
if (offset == 0) {
return apply_core(e, 0);
} else {
// The apply_core(e, 0) may seem redundant, but it allows us to
// mark nested closed expressions.
return apply_core(e, 0) && apply_core(e, offset);
}
}
bool apply_core(expr const & e, unsigned offset) {
bool shared = false;
if (is_shared(e)) { if (is_shared(e)) {
shared = true;
expr_cell_offset p(e.raw(), offset); expr_cell_offset p(e.raw(), offset);
if (m_visited.find(p) != m_visited.end()) if (m_cached.find(p) != m_cached.end())
return false; return false;
m_visited.insert(p);
} }
bool result = false; bool result = false;
@ -63,34 +69,87 @@ protected:
break; break;
} }
if (m_set_closed_flag && !result && offset == 0) if (!result) {
e.raw()->set_closed(); if (offset == 0)
e.raw()->set_closed();
if (shared)
m_cached.insert(expr_cell_offset(e.raw(), offset));
}
return result; return result;
} }
public: public:
has_free_vars_fn(bool s):m_set_closed_flag(s) {} has_free_vars_fn() {}
bool operator()(expr const & e) { return apply(e, 0); } bool operator()(expr const & e) { return apply(e, 0); }
}; };
bool has_free_vars(expr const & e) { bool has_free_vars(expr const & e) {
return has_free_vars_fn(true)(e); return has_free_vars_fn()(e);
} }
/** \brief Functional object for checking whether a kernel expression has a free variable in the range <tt>[low, high)</tt> or not. */ /** \brief Functional object for checking whether a kernel expression has a free variable in the range <tt>[low, high)</tt> or not. */
class has_free_var_in_range_fn : public has_free_vars_fn { class has_free_var_in_range_fn {
unsigned m_low; protected:
unsigned m_high; unsigned m_low;
virtual bool process_var(expr const & x, unsigned offset) { unsigned m_high;
return var_idx(x) >= offset + m_low && var_idx(x) < offset + m_high; expr_cell_offset_set m_cached;
bool apply(expr const & e, unsigned offset) {
// handle easy cases
switch (e.kind()) {
case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value:
return false;
case expr_kind::Var:
return var_idx(e) >= offset + m_low && var_idx(e) < offset + m_high;
case expr_kind::App: case expr_kind::Eq: case expr_kind::Lambda: case expr_kind::Pi: case expr_kind::Let:
break;
}
if (e.raw()->is_closed())
return false;
bool shared = false;
if (is_shared(e)) {
shared = true;
expr_cell_offset p(e.raw(), offset);
if (m_cached.find(p) != m_cached.end())
return false;
}
bool result = false;
switch (e.kind()) {
case expr_kind::Constant: case expr_kind::Type: case expr_kind::Value: case expr_kind::Var:
// easy cases were already handled
lean_unreachable(); return false;
case expr_kind::App:
result = std::any_of(begin_args(e), end_args(e), [=](expr const & arg){ return apply(arg, offset); });
break;
case expr_kind::Eq:
result = apply(eq_lhs(e), offset) || apply(eq_rhs(e), offset);
break;
case expr_kind::Lambda:
case expr_kind::Pi:
result = apply(abst_domain(e), offset) || apply(abst_body(e), offset + 1);
break;
case expr_kind::Let:
result = apply(let_value(e), offset) || apply(let_body(e), offset + 1);
break;
}
if (!result && shared) {
m_cached.insert(expr_cell_offset(e.raw(), offset));
}
return result;
} }
public: public:
has_free_var_in_range_fn(unsigned low, unsigned high): has_free_var_in_range_fn(unsigned low, unsigned high):
has_free_vars_fn(false /* We should not set the closed flag since we are only considering a range of free variables */),
m_low(low), m_low(low),
m_high(high) { m_high(high) {
lean_assert(low < high); lean_assert(low < high);
} }
bool operator()(expr const & e) { return apply(e, 0); }
}; };
bool has_free_var(expr const & e, unsigned vidx) { bool has_free_var(expr const & e, unsigned vidx) {

View file

@ -40,9 +40,27 @@ static void tst2() {
lean_assert(!closed(abst_body(t))); lean_assert(!closed(abst_body(t)));
} }
static void tst3() {
unsigned n = 30000;
unsigned m = 10;
expr f = Const("f");
expr a = Const("a");
expr r = f(a, Var(m));
expr b = Const("Bool");
for (unsigned i = 0; i < n; i++)
r = mk_lambda(name(), b, r);
lean_assert(closed(r));
bool flag = true;
while (is_lambda(r)) {
flag = flag && closed(r);
r = abst_body(r);
}
}
int main() { int main() {
continue_on_violation(true); continue_on_violation(true);
tst1(); tst1();
tst2(); tst2();
tst3();
return has_violations() ? 1 : 0; return has_violations() ? 1 : 0;
} }