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patch: optimize selects by extracting exclusive branches #205

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patch: optimize selects by extracting exclusive branches #205

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2 changes: 2 additions & 0 deletions include/ctll/list.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,8 @@ template <typename T> struct item_matcher {
static constexpr auto check(...) { return std::false_type{}; }
static constexpr auto select(T) { return not_selected{}; }
template <typename Y> static constexpr auto select(Y) { return wrapper<Y>{}; }
static constexpr auto pick(std::true_type) { return wrapper<Y>{}; };
static constexpr auto pick(std::false_type) { return not_selected{}; };
};

template <typename T, typename... Ts> constexpr bool exists_in(T, list<Ts...>) noexcept {
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1 change: 1 addition & 0 deletions include/ctre/atoms.hpp
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Expand Up @@ -20,6 +20,7 @@ struct any { };
// actual AST of regexp
template <auto... Str> struct string { };
template <typename... Opts> struct select { };
template <typename... Opts> struct non_exclusive_select { };
template <typename... Content> struct sequence { };
struct empty { };

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125 changes: 122 additions & 3 deletions include/ctre/evaluation.hpp
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Expand Up @@ -135,13 +135,116 @@ constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, c
return evaluate(begin, result.position, last, consumed_something(f, sizeof...(String) > 0), captures, ctll::list<Tail...>());
}

template <typename T, typename... Ts> constexpr auto collides_with(T, ctll::list<Ts...>) noexcept {
return decltype((ctll::list<>{} + ... + ctll::item_matcher<Ts>::pick(
typename std::conditional<collides(calculate_first(sequence<T>{}), calculate_first(sequence<Ts>{})), std::true_type, std::false_type>::type{}
))){};
}

template <typename T, typename... Ts> constexpr auto collides_with_negated(T, ctll::list<Ts...>) noexcept {
return decltype((ctll::list<>{} + ... + ctll::item_matcher<Ts>::pick(
typename std::conditional<collides(ctre::negative_set<decltype(calculate_first(sequence<T>{}))>{}, calculate_first(sequence<Ts>{})), std::true_type, std::false_type>::type{}
))){};
}

template <typename T, typename... Ts> constexpr auto mutually_exclusive_with(T, ctll::list<Ts...>) noexcept {
return decltype((ctll::list<>{} + ... + ctll::item_matcher<Ts>::pick(
typename std::conditional<!collides(calculate_first(sequence<T>{}), calculate_first(sequence<Ts>{})), std::true_type, std::false_type>::type{}
))){};
}

namespace detail {
template <typename... Content>
constexpr auto transform_into_set(ctll::list<Content...>) {
return ctre::set<decltype(Content{})...>{};
//return ctre::set<decltype(transform_into_set(Content{}))... > {};
}

template <typename T>
constexpr auto transform_into_set(T) {
return T{};
}

template<>
constexpr auto transform_into_set(can_be_anything) {
return ctre::char_range<std::numeric_limits<int64_t>::min(), std::numeric_limits<int64_t>::max()>{};
}

template <typename... Content>
constexpr auto transform_into_select(ctll::list<Content...>) {
return ctre::select<decltype(Content{})...>{};
}
}

// matching select in patterns
template <typename R, typename Iterator, typename EndIterator, typename HeadOptions, typename... TailOptions, typename... Tail>
constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, const EndIterator last, const flags & f, R captures, ctll::list<select<HeadOptions, TailOptions...>, Tail...>) noexcept {
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>())) {
return r;
if constexpr (sizeof...(TailOptions) > 1) {
constexpr auto collision_list = collides_with(sequence<HeadOptions, Tail...>{}, ctll::list<
decltype(sequence<TailOptions, Tail...>{})...
>{});

if constexpr (ctll::empty(collision_list)) {
using set_type = decltype(detail::transform_into_set(calculate_first(sequence<HeadOptions, Tail...>{})));
if constexpr (::std::is_same_v<set<>, set_type>) {
//fail handle as normal
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>())) {
return r;
} else {
return evaluate(begin, current, last, f, captures, ctll::list<select<TailOptions...>, Tail...>());
}
} else {
//ok optimize into exclusive select
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<set_type, end_cycle_mark>{})) {
return evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>{});
} else {
return evaluate(begin, current, last, f, captures, ctll::list<select<TailOptions...>, Tail...>());
}
}

return evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>());
} else if constexpr (ctll::size(collision_list) == sizeof...(TailOptions)) {
//continue as normal...we collided with everything
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>())) {
return r;
} else {
return evaluate(begin, current, last, f, captures, ctll::list<select<TailOptions...>, Tail...>());
}
} else {
//we collided with some things, but not others, bifricate on the first character we see
//may be less computationally expensive to do a set subtraction from the complete list with the collision list, because we're evaluating collisions again
constexpr auto negated_collision_list = collides_with_negated(sequence<HeadOptions, Tail...>{}, ctll::list<
decltype(sequence<TailOptions, Tail...>{})...
>{});

using set_type = decltype(detail::transform_into_set(calculate_first(sequence<HeadOptions, Tail...>{})));
if constexpr (::std::is_same_v<set<>, set_type>) {
//fail
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>())) {
return r;
} else {
return evaluate(begin, current, last, f, captures, ctll::list<non_exclusive_select<TailOptions...>, Tail...>());
}
} else {
//ok optimize into a split
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<set_type, end_cycle_mark>{})) {
if (auto r2 = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>{})) {
return r2;
} else {
return evaluate(begin, current, last, f, captures, detail::transform_into_select(collision_list));
}
} else {
return evaluate(begin, current, last, f, captures, detail::transform_into_select(negated_collision_list));
}
}
}
} else {
return evaluate(begin, current, last, f, captures, ctll::list<select<TailOptions...>, Tail...>());
//simple case, too few branches to pick handle as normal
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>())) {
return r;
} else {
return evaluate(begin, current, last, f, captures, ctll::list<select<TailOptions...>, Tail...>());
}
}
}

Expand All @@ -151,6 +254,22 @@ constexpr CTRE_FORCE_INLINE R evaluate(const Iterator, Iterator, const EndIterat
return not_matched;
}

// non exclusive select (assume collisions)
template <typename R, typename Iterator, typename EndIterator, typename HeadOptions, typename... TailOptions, typename... Tail>
constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, const EndIterator last, const flags & f, R captures, ctll::list<non_exclusive_select<HeadOptions, TailOptions...>, Tail...>) noexcept {
if (auto r = evaluate(begin, current, last, f, captures, ctll::list<HeadOptions, Tail...>())) {
return r;
} else {
return evaluate(begin, current, last, f, captures, ctll::list<non_exclusive_select<TailOptions...>, Tail...>());
}
}

template <typename R, typename Iterator, typename EndIterator, typename... Tail>
constexpr CTRE_FORCE_INLINE R evaluate(const Iterator, Iterator, const EndIterator, flags, R, ctll::list<non_exclusive_select<>, Tail...>) noexcept {
// no previous option was matched => REJECT
return not_matched;
}

// matching sequence in patterns
template <typename R, typename Iterator, typename EndIterator, typename HeadContent, typename... TailContent, typename... Tail>
constexpr CTRE_FORCE_INLINE R evaluate(const Iterator begin, Iterator current, const EndIterator last, const flags & f, R captures, ctll::list<sequence<HeadContent, TailContent...>, Tail...>) noexcept {
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