From 4a291705f46086d5adcf68de6d6d1441c4b9e4f9 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Thu, 8 May 2025 14:37:06 +0200
Subject: Built a working vtk file writer. Would prefer a lambda writer tbh

---
 c++/macroscopic.hpp | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

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

diff --git a/c++/macroscopic.hpp b/c++/macroscopic.hpp
index 43c727b..e126bbe 100644
--- a/c++/macroscopic.hpp
+++ b/c++/macroscopic.hpp
@@ -9,7 +9,7 @@ namespace lbm {
  */
 template<typename T, typename Desc>
 void compute_rho_u (
-		saw::data<sch::Cell<T, Desc, 0, 0, 1>>& dfs,
+		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
 	)
@@ -30,5 +30,34 @@ void compute_rho_u (
 		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[i] = vel[i] + saw::data<T>{dfi::directions[j][i]} * dfs(j);
+		}
+	}
+
+	for(size_t i = 0; i < Desc::D; ++i){
+		vel[i] = vel[i] / rho;
+	}
+}
 }
 }
-- 
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