random-selector

CMakeLists.txt

@@ -26,10 +26,6 @@ if(ND_WFC_BUILD_TESTS)
     add_subdirectory(tests)
 endif()
 
-if(ND_WFC_BUILD_EXAMPLES)
-    add_subdirectory(examples)
-endif()
-
 # Install configuration temporarily disabled
 # TODO: Fix install configuration
 # include(GNUInstallDirs)

include/nd-wfc/wfc.hpp

@@ -638,6 +638,7 @@ concept ConstrainerFunction = requires(T func, WorldT& world, size_t index, Worl
 template <typename T, typename VarT>
 concept RandomSelectorFunction = requires(T func, std::span<const VarT> possibleValues) {
     { func(possibleValues) } -> std::convertible_to<size_t>;
+    { func.rng(static_cast<uint32_t>(1)) } -> std::convertible_to<uint32_t>;
 };
 
 /**
@@ -653,11 +654,15 @@ public:
     constexpr explicit DefaultRandomSelector(uint32_t seed = 0x12345678) : m_seed(seed) {}
 
     constexpr size_t operator()(std::span<const VarT> possibleValues) const {
-        if (possibleValues.empty()) return 0;
+        constexpr_assert(!possibleValues.empty(), "possibleValues must not be empty");
 
         // Simple linear congruential generator for constexpr compatibility
+        return static_cast<size_t>(rng(possibleValues.size()));
+    }
+
+    constexpr uint32_t rng(uint32_t max) { 
         m_seed = m_seed * 1103515245 + 12345;
-        return static_cast<size_t>(m_seed) % possibleValues.size();
+        return m_seed % max; 
     }
 };
 
@@ -674,13 +679,141 @@ public:
     explicit AdvancedRandomSelector(std::mt19937& rng) : m_rng(rng) {}
 
     size_t operator()(std::span<const VarT> possibleValues) const {
-        if (possibleValues.empty()) return 0;
+        constexpr_assert(!possibleValues.empty(), "possibleValues must not be empty");
 
-        std::uniform_int_distribution<size_t> dist(0, possibleValues.size() - 1);
+        return rng(possibleValues.size());
+    }
+
+    uint32_t rng(uint32_t max) { 
+        std::uniform_int_distribution<uint32_t> dist(0, max);
         return dist(m_rng); 
     }
 };
 
+/**
+ * @brief Weight specification for a specific value
+ * @tparam Value The variable value
+ * @tparam Weight The 16-bit weight for this value
+ */
+ template <typename VarT, VarT Value, uint16_t WeightValue>
+ struct Weight {
+     static constexpr VarT value = Value;
+     static constexpr uint16_t weight = WeightValue;
+ };
+ 
+ /**
+  * @brief Compile-time weights storage for weighted random selection
+  * @tparam VarT The variable type
+  * @tparam VariableIDMapT The variable ID map type
+  * @tparam DefaultWeight The default weight for values not explicitly specified
+  * @tparam WeightSpecs Variadic template parameters of Weight<VarT, Value, Weight> specifications
+  */
+ template <typename VarT, typename VariableIDMapT, uint16_t DefaultWeight, typename... WeightSpecs>
+ class WeightsMap {
+ private:
+     static constexpr size_t NumWeights = sizeof...(WeightSpecs);
+ 
+     // Helper to get weight for a specific value
+     static consteval uint16_t GetWeightForValue(VarT targetValue) {
+         // Check each weight spec to find the target value
+         uint16_t weight = DefaultWeight;
+         ((WeightSpecs::value == targetValue ? weight = WeightSpecs::weight : weight), ...);
+         return weight;
+     }
+ 
+ public:
+     /**
+      * @brief Get the weight for a specific value at compile time
+      * @tparam TargetValue The value to get weight for
+      * @return The weight for the value
+      */
+     template <VarT TargetValue>
+     static consteval uint16_t GetWeight() {
+         return GetWeightForValue(TargetValue);
+     }
+ 
+     /**
+      * @brief Get weights array for all registered values
+      * @return Array of weights corresponding to all registered values
+      */
+     static consteval std::array<uint16_t, VariableIDMapT::ValuesRegisteredAmount> GetWeightsArray() {
+         std::array<uint16_t, VariableIDMapT::ValuesRegisteredAmount> weights{};
+ 
+         for (size_t i = 0; i < VariableIDMapT::ValuesRegisteredAmount; ++i) {
+             weights[i] = GetWeightForValue(VariableIDMapT::GetValueConsteval(i));
+         }
+ 
+         return weights;
+     }
+
+     static consteval uint32_t GetTotalWeight() {
+         uint32_t totalWeight = 0;
+         auto weights = GetWeightsArray();
+         for (size_t i = 0; i < VariableIDMapT::ValuesRegisteredAmount; ++i) {
+             totalWeight += weights[i];
+         }
+         return totalWeight;
+     }
+
+     static consteval std::array<uint32_t, VariableIDMapT::ValuesRegisteredAmount> GetCumulativeWeightsArray() {
+         auto weights = GetWeightsArray();
+         uint32_t totalWeight = 0;
+         std::array<uint32_t, VariableIDMapT::ValuesRegisteredAmount> cumulativeWeights{};
+         for (size_t i = 0; i < VariableIDMapT::ValuesRegisteredAmount; ++i) {
+             totalWeight += weights[i];
+             cumulativeWeights[i] = totalWeight;
+         }
+         return cumulativeWeights;
+     }
+ };
+ 
+ /**
+  * @brief Weighted random selector that uses another random selector as backend
+  * @tparam VarT The variable type
+  * @tparam VariableIDMapT The variable ID map type
+  * @tparam BackendSelectorT The backend random selector type
+  * @tparam WeightsMapT The weights map type containing weight specifications
+  */
+ template <typename VarT, typename VariableIDMapT, typename BackendSelectorT, typename WeightsMapT>
+ class WeightedSelector {
+ private:
+     BackendSelectorT m_backendSelector;
+     const std::array<uint16_t, VariableIDMapT::ValuesRegisteredAmount> m_weights;
+     const std::array<uint32_t, VariableIDMapT::ValuesRegisteredAmount> m_cumulativeWeights;
+ 
+ public:
+     explicit WeightedSelector(BackendSelectorT backendSelector)
+         : m_backendSelector(backendSelector)
+         , m_weights(WeightsMapT::GetWeightsArray())
+         , m_cumulativeWeights(WeightsMapT::GetCumulativeWeightsArray())
+     {}
+ 
+     explicit WeightedSelector(uint32_t seed)
+         requires std::is_same_v<BackendSelectorT, DefaultRandomSelector<VarT>>
+         : m_backendSelector(seed)
+         , m_weights(WeightsMapT::GetWeightsArray())
+         , m_cumulativeWeights(WeightsMapT::GetCumulativeWeightsArray())
+     {}
+ 
+     size_t operator()(std::span<const VarT> possibleValues) const {
+         constexpr_assert(!possibleValues.empty(), "possibleValues must not be empty");
+         constexpr_assert(possibleValues.size() == 1, "possibleValues must be a single value");
+ 
+         // Use backend selector to pick a random number in range [0, totalWeight)
+         uint32_t randomValue = m_backendSelector.rng(m_cumulativeWeights.back());
+ 
+         // Find which value this random value corresponds to
+         for (size_t i = 0; i < possibleValues.size(); ++i) {
+             if (randomValue <= m_cumulativeWeights[i]) {
+                 return i;
+             }
+         }
+ 
+         // Fallback (should not reach here)
+         return possibleValues.size() - 1;
+     }
+ };
+
 /**
  * @brief Builder class for creating WFC instances
  */
@@ -714,6 +847,10 @@ public:
         requires RandomSelectorFunction<NewRandomSelectorT, VarT>
     using SetRandomSelector = Builder<WorldT, VarT, VariableIDMapT, ConstrainerFunctionMapT, CallbacksT, NewRandomSelectorT>;
 
+    template <uint16_t DefaultWeight, typename... WeightSpecs>
+    using Weights = Builder<WorldT, VarT, VariableIDMapT, ConstrainerFunctionMapT, CallbacksT, WeightedSelector<VarT, VariableIDMapT, RandomSelectorT, WeightsMap<VarT, VariableIDMapT, DefaultWeight, WeightSpecs...>>>;
+
+
     using Build = WFC<WorldT, VarT, VariableIDMapT, ConstrainerFunctionMapT, CallbacksT, RandomSelectorT>;
 };