From f3dde8285baf87a89d2a9b79ac719573c47538ff Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Sat, 2 Sep 2023 18:04:18 +0200
Subject: c++: Generating example layouts

---
 c++/collide_and_stream.h   |  3 ---
 c++/descriptor.h           | 24 +++++++++----------
 c++/examples/cavity_2d.cpp | 57 +++++++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 68 insertions(+), 16 deletions(-)

diff --git a/c++/collide_and_stream.h b/c++/collide_and_stream.h
index 5682437..5cbb551 100644
--- a/c++/collide_and_stream.h
+++ b/c++/collide_and_stream.h
@@ -2,8 +2,5 @@
 
 namespace kel {
 namespace lbm {
-class bgk_dynamics {
-
-};
 }
 }
diff --git a/c++/descriptor.h b/c++/descriptor.h
index 4d29831..33fef9b 100644
--- a/c++/descriptor.h
+++ b/c++/descriptor.h
@@ -1,6 +1,6 @@
 #pragma once
 
-#include <forstio/codec/schema.h>
+#include <forstio/codec/data.h>
 
 namespace kel {
 namespace lbm {
@@ -32,24 +32,24 @@ template<typename T>
 class df_info{};
 
 template<typename T>
-class df_info<Descriptor<T, 2, 5>> {
-	static constexpr std::array<std::array<int32_t, 2>, 5> directions = {
+class df_info<schema::Descriptor<T, 2, 5>> {
+	static constexpr std::array<std::array<int32_t, 2>, 5> directions = {{
 		{ 0, 0},
 		{-1, 0},
 		{ 0,-1},
 		{ 0, 1},
 		{ 1, 0}
+	}};
+
+	static constexpr std::array<typename saw::native_data_type<T>::type,5> weights = {
+		1./3.,
+		1./6.,
+		1./6.,
+		1./6.,
+		1./6.
 	};
 
-	static constexpr std::array<std::ratio<int32_t>,5> weights = {
-		{1,3},
-		{1,6},
-		{1,6},
-		{1,6},
-		{1,6}
-	};
-
-	static constexpr std::ratio<int32_t> cs2 = {1,3};
+	static constexpr typename saw::native_data_type<T>::type cs2 = 1./3.;
 };
 }
 }
diff --git a/c++/examples/cavity_2d.cpp b/c++/examples/cavity_2d.cpp
index e06ba2d..88e53fe 100644
--- a/c++/examples/cavity_2d.cpp
+++ b/c++/examples/cavity_2d.cpp
@@ -17,7 +17,8 @@ namespace schema {
  * D factor
  * Q factor
  */
-using DfCell2DType = CellType<Float32, 2, 5, 0, 0, 1>;
+using T = Float32;
+using DfCell2DType = CellType<T, 2, 5, 0, 0, 1>;
 
 using CellInfo2DType = CellType<UInt8, 2, 5, 1, 0, 0>;
 
@@ -30,9 +31,59 @@ using Cell = CellData<
 >;
 
 }
+
+template<size_t D, size_t Q>
+class collision {
+public:
+	typename saw::native_data_type<schema::T>::type relaxation_;
+public:
+	std::array<typename saw::native_data_type<schema::T>::type,Q> equilibrium(
+		typename saw::native_data_type<schema::T>::type rho,
+		std::array<typename saw::native_data_type<schema::T>::type, D> vel
+	){
+		using dfi = df_info<schema::Descriptor<schema::T, D, Q>>;
+
+		typename std::array<saw::native_data_type<schema::T>::type,Q> eq;
+
+		for(std::size_t i = 0; i < eq.size(); ++i){
+			auto vel_c = (vel[0]*dfi::directions[i][0] + vel[1]*dfi::directions[i][1]);
+			auto vel_c_cs2 = vel_c / dfi::cs2;
+			eq[i] = dfi::weights[i] * rho * (
+				1
+				+ vel_c_cs2
+				+ vel_c_cs2 * vel_c_cs2
+				- ( vel[0] * vel[0] + vel[1] * vel[1] ) / ( 2. * dfi::cs2 )
+			);
+		}
+
+		return eq;
+		
+	}
+
+	void compute_rho_u(
+		saw::data<schema::DfCell2DType>& dfs,
+		typename saw::native_data_type<schema::T>::type& rho,
+		std::array<typename saw::native_data_type<schema::T>::type, 2>& vel
+	){
+		using dfi = df_info<schema::Descriptor<schema::T, D, Q>>;
+
+		rho = 0;
+		std::fill(vel.begin(), vel.end(), 0);
+
+		for(size_t i = 0; i < Q; ++i){
+			rho += dfs[i];
+			vel[0] += dfi::directions[i][0] * dfs.at(i).get();
+			vel[1] += dfi::directions[i][1] * dfs.at(i).get();
+		}
+
+		vel[0] /= rho;
+		vel[1] /= rho;
+	}
+};
 }
 }
 
+constexpr size_t dim_size = 2;
 constexpr size_t dim_x = 32;
 constexpr size_t dim_y = 32;
 
@@ -95,6 +146,10 @@ int main(){
 	 */
 	set_initial_conditions(lattice);
 
+	/**
+	 * Timeloop
+	 */
+
 	/**
 	 * Print basic setup info
 	 */
-- 
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