From 36b1707da0f71b08a7a992bfb6a0fccf1b7a356d Mon Sep 17 00:00:00 2001
From: Mateusz Pusz <mateusz.pusz@gmail.com>
Date: Sun, 24 Nov 2024 13:58:04 +0100
Subject: [PATCH] perf: `get_complexity`, `explode`, and
 `extract_convertible_quantities` results caching added

---
 .../mp-units/framework/quantity_spec.h        | 58 ++++++++++++++-----
 1 file changed, 44 insertions(+), 14 deletions(-)

diff --git a/src/core/include/mp-units/framework/quantity_spec.h b/src/core/include/mp-units/framework/quantity_spec.h
index 6226cdde1..c0395069d 100644
--- a/src/core/include/mp-units/framework/quantity_spec.h
+++ b/src/core/include/mp-units/framework/quantity_spec.h
@@ -622,7 +622,7 @@ template<typename Q>
 }
 
 template<QuantitySpec Q>
-[[nodiscard]] consteval int get_complexity(Q)
+[[nodiscard]] consteval int get_complexity_impl(Q)
 {
   if constexpr (DerivedQuantitySpec<Q>)
     return max(get_complexity(typename Q::_num_{}), get_complexity(typename Q::_den_{}));
@@ -632,6 +632,15 @@ template<QuantitySpec Q>
     return 0;
 }
 
+template<QuantitySpec Q>
+constexpr auto get_complexity_result = get_complexity_impl(Q{});
+
+template<QuantitySpec Q>
+[[nodiscard]] consteval int get_complexity(Q)
+{
+  return get_complexity_result<Q>;
+}
+
 // dimension_one is always the last one
 // otherwise, sort by typename
 template<Dimension D1, Dimension D2>
@@ -719,14 +728,17 @@ explode_result(Q) -> explode_result<Q>;
 
 #endif
 
-template<int Complexity, DerivedQuantitySpec Q>
+template<int Complexity, QuantitySpec Q>
 [[nodiscard]] consteval auto explode(Q q);
 
+template<int Complexity, DerivedQuantitySpec Q>
+[[nodiscard]] consteval auto explode_impl(Q q);
+
 template<int Complexity, NamedQuantitySpec Q>
-[[nodiscard]] consteval auto explode(Q q);
+[[nodiscard]] consteval auto explode_impl(Q q);
 
 template<int Complexity, QuantitySpec Q, typename Num, typename... Nums, typename Den, typename... Dens>
-[[nodiscard]] consteval auto explode(Q, type_list<Num, Nums...>, type_list<Den, Dens...>)
+[[nodiscard]] consteval auto explode_impl(Q, type_list<Num, Nums...>, type_list<Den, Dens...>)
 {
   constexpr auto num = get_complexity(Num{});
   constexpr auto den = get_complexity(Den{});
@@ -751,7 +763,7 @@ template<int Complexity, QuantitySpec Q, typename Num, typename... Nums, typenam
 }
 
 template<int Complexity, QuantitySpec Q, typename Num, typename... Nums>
-[[nodiscard]] consteval auto explode(Q, type_list<Num, Nums...>, type_list<>)
+[[nodiscard]] consteval auto explode_impl(Q, type_list<Num, Nums...>, type_list<>)
 {
   constexpr auto n = get_complexity(Num{});
   if constexpr (n == Complexity || !requires { explode_to_equation(Num{}); })
@@ -763,7 +775,7 @@ template<int Complexity, QuantitySpec Q, typename Num, typename... Nums>
 }
 
 template<int Complexity, QuantitySpec Q, typename Den, typename... Dens>
-[[nodiscard]] consteval auto explode(Q, type_list<>, type_list<Den, Dens...>)
+[[nodiscard]] consteval auto explode_impl(Q, type_list<>, type_list<Den, Dens...>)
 {
   constexpr auto den = get_complexity(Den{});
   if constexpr (den == Complexity || !requires { explode_to_equation(Den{}); })
@@ -776,24 +788,24 @@ template<int Complexity, QuantitySpec Q, typename Den, typename... Dens>
 }
 
 template<int Complexity, QuantitySpec Q>
-[[nodiscard]] consteval auto explode(Q, type_list<>, type_list<>)
+[[nodiscard]] consteval auto explode_impl(Q, type_list<>, type_list<>)
 {
   return explode_result{dimensionless};
 }
 
 template<int Complexity, DerivedQuantitySpec Q>
-[[nodiscard]] consteval auto explode(Q q)
+[[nodiscard]] consteval auto explode_impl(Q q)
 {
   constexpr auto complexity = get_complexity(Q{});
   if constexpr (complexity > Complexity)
-    return explode<Complexity>(q, type_list_sort<typename Q::_num_, type_list_of_ingredients_less>{},
-                               type_list_sort<typename Q::_den_, type_list_of_ingredients_less>{});
+    return explode_impl<Complexity>(q, type_list_sort<typename Q::_num_, type_list_of_ingredients_less>{},
+                                    type_list_sort<typename Q::_den_, type_list_of_ingredients_less>{});
   else
     return explode_result{q};
 }
 
 template<int Complexity, NamedQuantitySpec Q>
-[[nodiscard]] consteval auto explode(Q q)
+[[nodiscard]] consteval auto explode_impl(Q q)
 {
   constexpr auto complexity = get_complexity(Q{});
   if constexpr (complexity > Complexity && requires { Q::_equation_; }) {
@@ -803,6 +815,15 @@ template<int Complexity, NamedQuantitySpec Q>
     return explode_result{q};
 }
 
+template<int Complexity, QuantitySpec Q>
+constexpr auto explode_res = explode_impl<Complexity>(Q{});
+
+template<int Complexity, QuantitySpec Q>
+[[nodiscard]] consteval auto explode(Q)
+{
+  return explode_res<Complexity, Q>;
+}
+
 template<typename NumFrom, typename... NumsFrom, typename DenFrom, typename... DensFrom, typename NumTo,
          typename... NumsTo, typename DenTo, typename... DensTo>
 [[nodiscard]] consteval specs_convertible_result are_ingredients_convertible(type_list<NumFrom, NumsFrom...> num_from,
@@ -889,10 +910,8 @@ extract_results(bool, From = {}, To = {}, prepend_rest = {}, Elem = {}) -> extra
 
 #endif
 
-// tries to find the largest common power of a quantity
-// in case powers have different factors of the same dimension, returns the remainder
 template<typename From, typename To>
-[[nodiscard]] consteval auto extract_convertible_quantities(From, To)
+[[nodiscard]] consteval auto extract_convertible_quantities_impl(From, To)
 {
   constexpr auto qfrom = map_power(From{});
   constexpr auto qto = map_power(To{});
@@ -925,6 +944,17 @@ template<typename From, typename To>
   }
 }
 
+template<typename From, typename To>
+constexpr auto extract_convertible_quantities_result = extract_convertible_quantities_impl(From{}, To{});
+
+// tries to find the largest common power of a quantity
+// in case powers have different factors of the same dimension, returns the remainder
+template<typename From, typename To>
+[[nodiscard]] consteval auto extract_convertible_quantities(From, To)
+{
+  return extract_convertible_quantities_result<From, To>;
+}
+
 enum class extracted_entities : std::int8_t { numerators, denominators, from, to };
 
 template<extracted_entities Entities, auto Ext, TypeList NumFrom, TypeList DenFrom, TypeList NumTo, TypeList DenTo>