From 24bf28a8fb9cc8c3a90b77de9b60728bece7885d Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Sat, 18 Oct 2025 18:01:14 +0200
Subject: Moving project structure for more less compilation

---
 lib/c++/collision.hpp | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 lib/c++/collision.hpp

(limited to 'lib/c++/collision.hpp')

diff --git a/lib/c++/collision.hpp b/lib/c++/collision.hpp
new file mode 100644
index 0000000..9ab542b
--- /dev/null
+++ b/lib/c++/collision.hpp
@@ -0,0 +1,129 @@
+#pragma once
+
+#include "macroscopic.hpp"
+#include "component.hpp"
+#include "equilibrium.hpp"
+
+namespace kel {
+namespace lbm {
+namespace cmpt {
+struct BGK {};
+struct BGKGuo {};
+}
+
+/**
+ * Standard BGK collision operator for LBM
+ */
+template<typename T, typename Descriptor, typename Encode>
+class component<T, Descriptor, cmpt::BGK, Encode> {
+private:
+	typename saw::native_data_type<T>::type relaxation_;
+	saw::data<T> frequency_;
+public:
+	component(typename saw::native_data_type<T>::type relaxation__):
+		relaxation_{relaxation__},
+		frequency_{typename saw::native_data_type<T>::type(1) / relaxation_}
+	{}
+
+	using Component = cmpt::BGK;
+
+	/**
+	 * Thoughts regarding automating order setup
+	 */
+	using access = cmpt::access_tuple<
+		cmpt::access<"dfs", 1, true, true, true>
+	>;
+
+	/**
+	 * Thoughts regarding automating order setup
+	 */
+	static constexpr saw::string_literal name = "collision";
+	static constexpr saw::string_literal after = "";
+	static constexpr saw::string_literal before = "streaming";
+
+	/**
+	 * Raw setup
+	 */
+	template<typename CellFieldSchema>
+	void apply(saw::data<CellFieldSchema, Encode>& field, saw::data<sch::FixedArray<sch::UInt64,Descriptor::D>> index, uint64_t time_step){
+		bool is_even = ((time_step % 2) == 0);
+		auto& cell = field(index);
+
+		auto& dfs_old = (is_even) ? cell.template get<"dfs_old">() : cell.template get<"dfs">();
+		// auto& dfs = (not is_even) ? cell.template get<"dfs_old">() : cell.template get<"dfs">();
+
+		saw::data<T> rho;
+		saw::data<sch::FixedArray<T,Descriptor::D>> vel;
+		compute_rho_u<T,Descriptor>(dfs_old,rho,vel);
+		auto eq = equilibrium<T,Descriptor>(rho,vel);
+
+		for(uint64_t i = 0u; i < Descriptor::Q; ++i){
+			dfs_old({i}) = dfs_old({i}) + frequency_ * (eq.at(i) - dfs_old({i}));
+			// dfs_old({i}).set(dfs_old({i}).get() + (1.0 / relaxation_) * (eq.at(i).get() - dfs_old({i}).get()));
+		}
+	}
+};
+
+template<typename T, typename Descriptor, typename Encode>
+class component<T, Descriptor, cmpt::BGKGuo, Encode> {
+private:
+	typename saw::native_data_type<T>::type relaxation_;
+	saw::data<T> frequency_;
+public:
+	component(typename saw::native_data_type<T>::type relaxation__):
+		relaxation_{relaxation__},
+		frequency_{typename saw::native_data_type<T>::type(1) / relaxation_}
+	{}
+
+	using Component = cmpt::BGKGuo;
+
+	using access = cmpt::access_tuple<
+		cmpt::access<"dfs", 1, true, true, true>,
+		cmpt::access<"force", 0, true, false>
+	>;
+
+	/**
+	 * Thoughts regarding automating order setup
+	 */
+	static constexpr saw::string_literal name = "collision";
+	static constexpr saw::string_literal after = "";
+	static constexpr saw::string_literal before = "streaming";
+
+	template<typename CellFieldSchema>
+	void apply(saw::data<CellFieldSchema, Encode>& field, saw::data<sch::FixedArray<sch::UInt64, Descriptor::D>> index, uint64_t time_step){
+		bool is_even = ((time_step % 2) == 0);
+		auto& cell = field(index);
+
+		auto& dfs_old = (is_even) ? cell.template get<"dfs_old">() : cell.template get<"dfs">();
+		// auto& dfs = (not is_even) ? cell.template get<"dfs_old">() : cell.template get<"dfs">();
+
+		saw::data<T> rho;
+		saw::data<sch::FixedArray<T,Descriptor::D>> vel;
+		compute_rho_u<T,Descriptor>(dfs_old,rho,vel);
+		auto eq = equilibrium<T,Descriptor>(rho,vel);
+
+		using dfi = df_info<T,Descriptor>;
+
+		auto& force = cell.template get<"force">();
+
+		for(uint64_t i = 0u; i < Descriptor::Q; ++i){
+			// saw::data<T> ci_min_u{0};
+			saw::data<T> ci_dot_u{0};
+			for(uint64_t d = 0u; d < Descriptor::D; ++d){
+				ci_dot_u = ci_dot_u + vel.at({d}) * saw::data<T>{static_cast<typename saw::native_data_type<T>::type>(dfi::directions[i][d])};
+			}
+			saw::data<T> F_i{0};// = saw::data<T>{dfi::weights[i]} * (ci_dot_F * dfi::inv_cs2 + ci_dot_u * ci_dot_F * (dfi::inv_cs2 * dfi::inv_cs2));
+
+			for(uint64_t d = 0u; d < Descriptor::D; ++d){
+				F_i = F_i +
+					saw::data<T>{dfi::weights[i]} * ((saw::data<T>{static_cast<typename saw::native_data_type<T>::type>(dfi::directions[i][d])}
+					- vel.at({d}) ) * dfi::inv_cs2 + ci_dot_u * saw::data<T>{static_cast<typename saw::native_data_type<T>::type>(dfi::directions[i][d])} * dfi::inv_cs2  * dfi::inv_cs2 ) * force({d});
+			}
+
+
+			dfs_old({i}) = dfs_old({i}) + frequency_ * (eq.at(i) - dfs_old({i}) ) + F_i * (saw::data<T>{1} - saw::data<T>{0.5f} * frequency_);
+		}
+	}
+};
+}
+}
-- 
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