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refactor(kernel/default_converter): separate lazy_delta_reduction procedure

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This commit is contained in:
Leonardo de Moura 2015-06-22 08:45:05 -07:00
parent 1c70514231
commit a518a45239
2 changed files with 78 additions and 46 deletions
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118
src/kernel/default_converter.cpp
View file

@ -466,6 +466,77 @@ void default_converter::cache_failure(expr const & t, expr const & s) {
m_failure_cache.insert(mk_pair(s, t));
}
/**
\brief Perform one lazy delta-reduction step.
Return
- l_true if t_n and s_n are definitionally equal.
- l_false if they are not definitionally equal.
- l_undef it the step did not manage to establish whether they are definitionally equal or not.
\remark t_n, s_n and cs are updated.
*/
auto default_converter::lazy_delta_reduction_step(expr & t_n, expr & s_n, constraint_seq & cs) -> lazy_delta_result {
auto d_t = is_delta(t_n);
auto d_s = is_delta(s_n);
if (!d_t && !d_s) {
return lazy_delta_result::DefUnknown;
} else if (d_t && !d_s) {
t_n = whnf_core(unfold_names(t_n, 0));
} else if (!d_t && d_s) {
s_n = whnf_core(unfold_names(s_n, 0));
} else if (d_t->get_weight() > d_s->get_weight()) {
t_n = whnf_core(unfold_names(t_n, d_s->get_weight() + 1));
} else if (d_t->get_weight() < d_s->get_weight()) {
s_n = whnf_core(unfold_names(s_n, d_t->get_weight() + 1));
} else {
lean_assert(d_t && d_s && d_t->get_weight() == d_s->get_weight());
if (is_app(t_n) && is_app(s_n) && is_eqp(*d_t, *d_s)) {
// If t_n and s_n are both applications of the same (non-opaque) definition,
if (has_expr_metavar(t_n) || has_expr_metavar(s_n)) {
// We let the unifier deal with cases such as
// (f ...) =?= (f ...)
// when t_n or s_n contains metavariables
return lazy_delta_result::DefUnknown;
} else {
// Optimization:
// We try to check if their arguments are definitionally equal.
// If they are, then t_n and s_n must be definitionally equal, and we can
// skip the delta-reduction step.
// If the flag use_conv_opt() is not true, then we skip this optimization
constraint_seq tmp_cs;
if (!is_opaque(*d_t) && d_t->use_conv_opt() && !failed_before(t_n, s_n)) {
if (is_def_eq(const_levels(get_app_fn(t_n)), const_levels(get_app_fn(s_n)), tmp_cs) &&
is_def_eq_args(t_n, s_n, tmp_cs)) {
cs += tmp_cs;
return lazy_delta_result::DefEqual;
} else {
cache_failure(t_n, s_n);
}
}
}
}
t_n = whnf_core(unfold_names(t_n, d_t->get_weight() - 1));
s_n = whnf_core(unfold_names(s_n, d_s->get_weight() - 1));
}
switch (quick_is_def_eq(t_n, s_n, cs)) {
case l_true: return lazy_delta_result::DefEqual;
case l_false: return lazy_delta_result::DefDiff;
case l_undef: return lazy_delta_result::Continue;
}
lean_unreachable();
}
lbool default_converter::lazy_delta_reduction(expr & t_n, expr & s_n, constraint_seq & cs) {
while (true) {
switch (lazy_delta_reduction_step(t_n, s_n, cs)) {
case lazy_delta_result::Continue: break;
case lazy_delta_result::DefUnknown: return l_undef;
case lazy_delta_result::DefEqual: return l_true;
case lazy_delta_result::DefDiff: return l_false;
}
}
}
pair<bool, constraint_seq> default_converter::is_def_eq_core(expr const & t, expr const & s) {
check_system("is_definitionally_equal");
constraint_seq cs;
@ -485,52 +556,9 @@ pair<bool, constraint_seq> default_converter::is_def_eq_core(expr const & t, exp
// lazy delta-reduction and then normalizer extensions
while (true) {
// first, keep applying lazy delta-reduction while applicable
while (true) {
auto d_t = is_delta(t_n);
auto d_s = is_delta(s_n);
if (!d_t && !d_s) {
break;
} else if (d_t && !d_s) {
t_n = whnf_core(unfold_names(t_n, 0));
} else if (!d_t && d_s) {
s_n = whnf_core(unfold_names(s_n, 0));
} else if (d_t->get_weight() > d_s->get_weight()) {
t_n = whnf_core(unfold_names(t_n, d_s->get_weight() + 1));
} else if (d_t->get_weight() < d_s->get_weight()) {
s_n = whnf_core(unfold_names(s_n, d_t->get_weight() + 1));
} else {
lean_assert(d_t && d_s && d_t->get_weight() == d_s->get_weight());
if (is_app(t_n) && is_app(s_n) && is_eqp(*d_t, *d_s)) {
// If t_n and s_n are both applications of the same (non-opaque) definition,
if (has_expr_metavar(t_n) || has_expr_metavar(s_n)) {
// We let the unifier deal with cases such as
// (f ...) =?= (f ...)
// when t_n or s_n contains metavariables
break;
} else {
// Optimization:
// We try to check if their arguments are definitionally equal.
// If they are, then t_n and s_n must be definitionally equal, and we can
// skip the delta-reduction step.
// If the flag use_conv_opt() is not true, then we skip this optimization
constraint_seq tmp_cs;
if (!is_opaque(*d_t) && d_t->use_conv_opt() && !failed_before(t_n, s_n)) {
if (is_def_eq(const_levels(get_app_fn(t_n)), const_levels(get_app_fn(s_n)), tmp_cs) &&
is_def_eq_args(t_n, s_n, tmp_cs)) {
cs += tmp_cs;
return to_bcs(true, cs);
} else {
cache_failure(t_n, s_n);
}
}
}
}
t_n = whnf_core(unfold_names(t_n, d_t->get_weight() - 1));
s_n = whnf_core(unfold_names(s_n, d_s->get_weight() - 1));
}
r = quick_is_def_eq(t_n, s_n, cs);
r = lazy_delta_reduction(t_n, s_n, cs);
if (r != l_undef) return to_bcs(r == l_true, cs);
}
// try normalizer extensions
auto new_t_n = d_norm_ext(t_n, cs);
auto new_s_n = d_norm_ext(s_n, cs);

4
src/kernel/default_converter.h
View file

@ -78,6 +78,10 @@ protected:
pair<bool, constraint_seq> is_def_eq_core(expr const & t, expr const & s);
pair<bool, constraint_seq> is_def_eq(expr const & t, expr const & s);
enum class lazy_delta_result { Continue, DefUnknown, DefEqual, DefDiff };
lazy_delta_result lazy_delta_reduction_step(expr & t_n, expr & s_n, constraint_seq & cs);
lbool lazy_delta_reduction(expr & t_n, expr & s_n, constraint_seq & cs);
public:
default_converter(environment const & env, bool memoize = true);