From 0ba2bc42e7ffaf71983dc9a8a1c59853c50a2cc2 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Mon, 14 Aug 2023 03:55:48 +0200
Subject: c++: Going into the area of simple BGK Dynamics

---
 c++/collide_and_stream.h   |  9 ++++++
 c++/descriptor.h           | 24 ++++++++++++++
 c++/examples/cavity_2d.cpp | 80 ++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 110 insertions(+), 3 deletions(-)
 create mode 100644 c++/collide_and_stream.h

diff --git a/c++/collide_and_stream.h b/c++/collide_and_stream.h
new file mode 100644
index 0000000..5682437
--- /dev/null
+++ b/c++/collide_and_stream.h
@@ -0,0 +1,9 @@
+#pragma once
+
+namespace kel {
+namespace lbm {
+class bgk_dynamics {
+
+};
+}
+}
diff --git a/c++/descriptor.h b/c++/descriptor.h
index c09b312..4d29831 100644
--- a/c++/descriptor.h
+++ b/c++/descriptor.h
@@ -27,5 +27,29 @@ using CellData = Struct<
 template<typename T, size_t D>
 using Lattice = Array<T, D>;
 }
+
+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 = {
+		{ 0, 0},
+		{-1, 0},
+		{ 0,-1},
+		{ 0, 1},
+		{ 1, 0}
+	};
+
+	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};
+};
 }
 }
diff --git a/c++/examples/cavity_2d.cpp b/c++/examples/cavity_2d.cpp
index 0f96a65..e06ba2d 100644
--- a/c++/examples/cavity_2d.cpp
+++ b/c++/examples/cavity_2d.cpp
@@ -2,6 +2,8 @@
 
 #include <forstio/codec/data.h>
 
+#include <iostream>
+
 namespace kel {
 namespace lbm {
 namespace schema {
@@ -31,8 +33,23 @@ using Cell = CellData<
 }
 }
 
+constexpr size_t dim_x = 32;
+constexpr size_t dim_y = 32;
+
+struct rectangle {
+	std::array<size_t,4> data_;
+
+	rectangle(size_t x, size_t y, size_t w, size_t h):
+		data_{x,y,w,h}
+	{}
+
+	bool inside(size_t i, size_t j) const {
+		return !(i < data_[0] || i > (data_[0]+data_[2]) || j < data_[1] || j > (data_[1] +data_[3]));
+	}
+};
+
 template<typename Func, typename Schema, size_t Dim>
-void apply_for_cells(Func&& func, saw::data<saw::schema::Array<Schema, Dim>, saw::encode::Native>& dat ){
+void apply_for_cells(Func&& func, saw::data<saw::schema::Array<Schema, Dim>>& dat){
 	for(std::size_t i = 0; i < dat.get_dim_size(0); ++i){
 		for(std::size_t j = 0; j < dat.get_dim_size(1); ++j){
 			func(dat.at(i,j), i, j);
@@ -40,14 +57,71 @@ void apply_for_cells(Func&& func, saw::data<saw::schema::Array<Schema, Dim>, saw
 	}
 }
 
+void set_geometry(saw::data<kel::lbm::schema::Lattice<kel::lbm::schema::Cell,2>>& latt){
+	using namespace kel::lbm;
+	apply_for_cells([](auto& cell, std::size_t i, std::size_t j){
+		uint8_t val = 0;
+		if(i == 1){
+			val = 2;
+		}
+		if(j == 1 || (i+2) == dim_x || (j+2) == dim_y){
+			val = 3;
+		}
+		if(i == 0 || j == 0 || (i+1) == dim_x || (j+1) == dim_y){
+			val = 1;
+		}
+		cell.template get<"info">().at(0).set(val);
+	}, latt);
+}
+
+void set_initial_conditions(saw::data<kel::lbm::schema::Lattice<kel::lbm::schema::Cell,2>>& latt){
+	using namespace kel::lbm;
+	apply_for_cells([](auto& cell, std::size_t i, std::size_t j){
+		cell.template get<"dfs">().at(0).set(1.0);
+	}, latt);
+}
+
 int main(){
 	using namespace kel::lbm;
 
-	saw::data<schema::Lattice<kel::lbm::schema::Cell,2>, saw::encode::Native> lattice{512, 512};
+	saw::data<schema::Lattice<kel::lbm::schema::Cell,2>, saw::encode::Native> lattice{dim_x, dim_y};
+
+	/**
+	 * Set meta information describing what this cell is
+	 */
+	set_geometry(lattice);
+	/**
+	 * 
+	 */
+	set_initial_conditions(lattice);
 
+	/**
+	 * Print basic setup info
+	 */
 	apply_for_cells([](auto& cell, std::size_t i, std::size_t j){
-		// cell.get<"info">();
+			// Not needed
+			(void) i;
+			std::cout<<static_cast<uint32_t>(cell.template get<"info">().at(0).get());
+			if( (j+1) < dim_y){
+				std::cout<<" ";
+			}else{
+				std::cout<<"\n";
+			}
 	}, lattice);
+	
+	std::cout<<"\n";
+	apply_for_cells([](auto& cell, std::size_t i, std::size_t j){
+			// Not needed
+			(void) i;
+			std::cout<<cell.template get<"dfs">().at(0).get();
+			if( (j+1) < dim_y){
+				std::cout<<" ";
+			}else{
+				std::cout<<"\n";
+			}
+	}, lattice);
+
+	std::cout<<std::endl;
 
 	return 0;
 }
-- 
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