From b9aacd9c2fdc61721c8ca3e1b40ebc92daa3772e Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Wed, 5 Nov 2025 13:38:04 +0100
Subject: Reworking structure

---
 lib/core/c++/macroscopic.hpp | 92 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 lib/core/c++/macroscopic.hpp

(limited to 'lib/core/c++/macroscopic.hpp')

diff --git a/lib/core/c++/macroscopic.hpp b/lib/core/c++/macroscopic.hpp
new file mode 100644
index 0000000..51368e9
--- /dev/null
+++ b/lib/core/c++/macroscopic.hpp
@@ -0,0 +1,92 @@
+#pragma once
+
+#include "descriptor.hpp"
+
+namespace kel {
+namespace lbm {
+/**
+ * Calculate the macroscopic variables rho and u in Lattice Units.
+ */
+template<typename T, typename Desc>
+void compute_rho_u (
+		const saw::data<sch::Cell<T, Desc, 0, 0, 1>>& dfs,
+		typename saw::native_data_type<T>::type& rho,
+		std::array<typename saw::native_data_type<T>::type, 2>& vel
+	)
+{
+	using dfi = df_info<T, Desc>;
+
+	rho = 0;
+	std::fill(vel.begin(), vel.end(), 0);
+
+	for(size_t j = 0; j < Desc::Q; ++j){
+		rho += dfs(j).get();
+		for(size_t i = 0; i < Desc::D; ++i){
+			vel[i] += dfi::directions[j][i] * dfs(j).get();
+		}
+	}
+
+	for(size_t i = 0; i < Desc::D; ++i){
+		vel[i] /= rho;
+	}
+}
+
+/**
+ * Calculate the macroscopic variables rho and u in Lattice Units.
+ */
+template<typename T, typename Desc>
+void compute_rho_u (
+		const saw::data<sch::Cell<T, Desc, 0, 0, 1>>& dfs,
+		saw::ref<saw::data<T>> rho,
+		saw::ref<saw::data<sch::FixedArray<T,Desc::D>>> vel
+	)
+{
+	using dfi = df_info<T, Desc>;
+
+	rho().set(0);
+	for(uint64_t i = 0; i < Desc::D; ++i){
+		vel().at({i}).set(0);
+	}
+
+	for(size_t j = 0; j < Desc::Q; ++j){
+		rho() = rho() + dfs(j);
+		for(size_t i = 0; i < Desc::D; ++i){
+			vel().at({i}) = vel().at({i}) + saw::data<T>{static_cast<typename saw::native_data_type<T>::type>(dfi::directions[j][i])} * dfs(j);
+		}
+	}
+
+	for(size_t i = 0; i < Desc::D; ++i){
+		vel().at({i}) = vel().at({i}) / rho();
+	}
+}
+
+/**
+ * Calculate the macroscopic variables rho and u in Lattice Units.
+ */
+template<typename T, typename Desc>
+void compute_rho_u (
+		const saw::data<sch::Cell<T, Desc, 0, 0, 1>>& dfs,
+		saw::ref<saw::data<T>> rho,
+		saw::ref<saw::data<sch::Vector<T,Desc::D>>> vel
+	)
+{
+	using dfi = df_info<T, Desc>;
+
+	rho().set(0);
+	for(uint64_t i = 0; i < Desc::D; ++i){
+		vel().at({{i}}).set(0);
+	}
+
+	for(size_t j = 0; j < Desc::Q; ++j){
+		rho() = rho() + dfs(j);
+		for(size_t i = 0; i < Desc::D; ++i){
+			vel().at({{i}}) = vel().at({{i}}) + saw::data<T>{static_cast<typename saw::native_data_type<T>::type>(dfi::directions[j][i])} * dfs(j);
+		}
+	}
+
+	for(size_t i = 0; i < Desc::D; ++i){
+		vel().at({{i}}) = vel().at({{i}}) / rho();
+	}
+}
+}
+}
-- 
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