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

---
 lib/core/c++/boundary.hpp   |  7 ++++---
 lib/core/c++/descriptor.hpp | 18 +++++++++---------
 2 files changed, 13 insertions(+), 12 deletions(-)

(limited to 'lib/core')

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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