1 files changed, 39 insertions, 0 deletions
diff --git a/c++/equilibrium.hpp b/c++/equilibrium.hpp
new file mode 100644
index 0000000..8342ed4
--- /dev/null
+++ b/c++/equilibrium.hpp
@@ -0,0 +1,39 @@
+#pragma once
+
+#include "descriptor.hpp"
+
+namespace kel {
+namespace lbm {
+template<typename T, typename Descriptor>
+saw::data<sch::FixedArray<T, Descriptor::Q>> equilibrium(saw::data<sch::T> rho, saw::data<sch::FixedArray<T,Descriptor::D>> vel){
+	using dfi = df_info<T, Descriptor>;
+
+	saw::data<sch::FixedArray<T,Descriptor::Q>> eq;
+	saw::data<T> vel_vel{};
+	for(uint64_t j = 0u; j < Descriptor::D; ++j){
+		vel_vel = vel_vel + vel.at(j) * vel.at(j);
+	}
+
+	for(uint64_t i = 0u; i < eq.get_dim_size<0u>(); ++i){
+		saw::data<T> vel_c{};
+		for(uint64_t j = 0u; j < Descriptor::D; ++j){
+			vel_c = vel_c + (vel.at(j) * {dfi::directions[i][j]});
+		}
+
+		auto vel_c_cs2 = vel_c * {dfi::inv_cs2};
+
+		eq.at(i).set(
+			dfi::weights[i] * rho.get() * 
+			(
+			 1.0
+			 + vel_c_cs2
+			 - dfi::inv_cs2 * 0.5 * vel_vel.get()
+			 + vel_c_cs2 * vel_c_cs2 * 0.5
+			)
+		);
+
+		return eq;
+	}
+}
+}
+}