From 0d3c1a0f68792a04129dc8da8e9b9b113f76e3ec Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Mon, 23 Mar 2026 16:41:32 +0100
Subject: Found wrong zou he boundary issue. Preparing for fix

---
 examples/poiseulle_particles_2d_psm_gpu/sim.cpp | 20 +++++++++-----------
 lib/core/c++/boundary.hpp                       |  7 ++++---
 lib/core/c++/descriptor.hpp                     | 18 +++++++++---------
 3 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/examples/poiseulle_particles_2d_psm_gpu/sim.cpp b/examples/poiseulle_particles_2d_psm_gpu/sim.cpp
index a8aeabb..0d356dd 100644
--- a/examples/poiseulle_particles_2d_psm_gpu/sim.cpp
+++ b/examples/poiseulle_particles_2d_psm_gpu/sim.cpp
@@ -202,7 +202,7 @@ saw::error_or<void> step(
 
 
 	q.submit([&](acpp::sycl::handler& h){
-		component<T,Desc,cmpt::PSM,encode::Sycl<saw::encode::Native>> collision{0.65};
+		component<T,Desc,cmpt::PSM,encode::Sycl<saw::encode::Native>> collision{0.8};
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
 
@@ -243,13 +243,13 @@ saw::error_or<void> step(
 					collision.apply(fields,macros,index,t_i);
 					break;
 				case 3u:
-					//flow_in.apply(fields,index,t_i);
-					equi.apply(fields,index,t_i);
+					flow_in.apply(fields,index,t_i);
+					//equi.apply(fields,index,t_i);
 					collision.apply(fields,macros,index,t_i);
 					break;
 				case 4u:
-					// flow_out.apply(fields,index,t_i);
-					equi.apply(fields,index,t_i);
+					flow_out.apply(fields,index,t_i);
+					// equi.apply(fields,index,t_i);
 					collision.apply(fields,macros,index,t_i);
 				break;
 				default:
@@ -295,12 +295,12 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 
 	converter<T> conv {
 		// delta_x
-		{{1.0}},
+		{{1e-3}},
 		// delta_t
-		{{1.0}}
+		{{1e-06}}
 	};
 	
-	print_lbm_meta<T,Desc>(conv,{0.05},{0.01},{0.4 * dim_y});
+	print_lbm_meta<T,Desc>(conv,{0.1},{1e-2},{0.4 * dim_y *1e-3});
 
 	// saw::data<sch::FixedArray<sch::UInt64,Desc::D>> meta{{dim_x,dim_y}};
 	auto lbm_data_ptr = saw::heap<saw::data<sch::ChunkStruct<T,Desc>>>();
@@ -382,8 +382,7 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			}
 		}
 		sycl_q.wait();
-		/*
-		{
+		if(i.get() %  1 == 0u){
 			{
 				auto eov = dev.copy_to_host(lbm_sycl_macro_data,*lbm_macro_data_ptr);
 				if(eov.is_error()){
@@ -397,7 +396,6 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 				}
 			}
 		}
-		*/
 		/*
 		{
 			{
diff --git a/lib/core/c++/boundary.hpp b/lib/core/c++/boundary.hpp
index adb473d..bb8eed9 100644
--- a/lib/core/c++/boundary.hpp
+++ b/lib/core/c++/boundary.hpp
@@ -206,16 +206,17 @@ public:
 		/**
 		 * Get the sum of the unknown dfs and precalculate the direction
 		 */
-		auto sum_unknown_dfs = (rho_setting_ - sum_df) * saw::data<FP>{known_dir};
+		auto sum_unknown_dfs = (rho_setting_ - sum_df);
+		auto unknown_dfs_dir = sum_unknown_dfs * saw::data<FP>{known_dir};
 
 		for(saw::data<sch::UInt64> k{0u}; k < saw::data<sch::UInt64>{Descriptor::Q}; ++k){
 			auto c_k = dfi::directions[k.get()];
 			if(c_k[0u]*known_dir < 0){
-				sum_unknown_dfs += dfs_old.at({k}) * c_k[0u];
+				unknown_dfs_dir += dfs_old.at({k}) * c_k[0u];
 			}
 		}
 
-		auto vel_x = sum_unknown_dfs / rho_setting_;
+		auto vel_x = unknown_dfs_dir / rho_setting_;
 
 		static_assert(Descriptor::D == 2u and Descriptor::Q == 9u, "Some parts are hard coded sadly");
 
diff --git a/lib/core/c++/descriptor.hpp b/lib/core/c++/descriptor.hpp
index 73f0cce..9f7399a 100644
--- a/lib/core/c++/descriptor.hpp
+++ b/lib/core/c++/descriptor.hpp
@@ -146,15 +146,15 @@ public:
 	static constexpr uint64_t Q = 9u;
 
 	static constexpr std::array<std::array<int32_t, D>, Q> directions = {{
-		{ 0, 0},
-		{-1, 0},
-		{ 1, 0},
-		{ 0,-1},
-		{ 0, 1},
-		{-1,-1},
-		{ 1, 1},
-		{-1, 1},
-		{ 1,-1}
+		{ 0, 0}, // 0
+		{-1, 0}, // 1
+		{ 1, 0}, // 2
+		{ 0,-1}, // 3
+		{ 0, 1}, // 4
+		{-1,-1}, // 5
+		{ 1, 1}, // 6
+		{-1, 1}, // 7
+		{ 1,-1}  // 8
 	}};
 
 	static constexpr std::array<typename saw::native_data_type<T>::type,Q> weights = {
-- 
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