From 7fd9bfd5946472230a3b74c52f88e19c15741faf Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Mon, 1 Jun 2026 17:21:44 +0200
Subject: I seem to have no clue what I'm doing

---
 lib/core/c++/collision.hpp      |  3 ++-
 lib/core/c++/math/n_closest.hpp | 18 ++++++++++++++----
 2 files changed, 16 insertions(+), 5 deletions(-)

(limited to 'lib')

diff --git a/lib/core/c++/collision.hpp b/lib/core/c++/collision.hpp
index 9c76c1a..023f61f 100644
--- a/lib/core/c++/collision.hpp
+++ b/lib/core/c++/collision.hpp
@@ -146,7 +146,8 @@ public:
 
 		saw::data<sch::Scalar<T>> half;
 		half.at({}).set(0.5);
-		saw::data<sch::Vector<T,Descriptor::D>> vel = vel_f.at(index) + total_force * ( half / rho );
+		auto& vel = vel_f.at(index);
+		vel = vel + total_force * ( half / rho );
 
 		compute_rho_u<T,Descriptor>(dfs_old_f.at(index),rho,vel);
 		auto eq = equilibrium<T,Descriptor>(rho,vel);
diff --git a/lib/core/c++/math/n_closest.hpp b/lib/core/c++/math/n_closest.hpp
index 13414e2..ac0fe2f 100644
--- a/lib/core/c++/math/n_closest.hpp
+++ b/lib/core/c++/math/n_closest.hpp
@@ -7,7 +7,7 @@ namespace kel {
 namespace lbm {
 
 template<typename FieldSchema, typename Encode, typename T, uint64_t D>
-saw::data<typename FieldSchema::InnerValueSchema> n_closest_read(const saw::data<sch::Ptr<FieldSchema>,Encode>& f, const saw::data<sch::Vector<T,D>>& frac_ind){
+saw::data<typename FieldSchema::StoredValueSchema> n_closest_read(const saw::data<sch::Ptr<FieldSchema>,Encode>& f, const saw::data<sch::Vector<T,D>>& frac_ind){
 
 	auto shift_frac_ind = frac_ind;
 	for(uint64_t i{0u}; i < D; ++i){
@@ -18,13 +18,16 @@ saw::data<typename FieldSchema::InnerValueSchema> n_closest_read(const saw::data
 		}
 	}
 
-	auto shift_ind = frac_ind.template cast_to<sch::UInt64>();
+	saw::data<sch::FixedArray<sch::UInt64,D>> shift_ind;
+	for(uint64_t i{0u}; i < D; ++i){
+		shift_ind.at({i}) = frac_ind.at({{i}}).template cast_to<sch::UInt64>();
+	}
 
 	return f.at(shift_ind);
 }
 
 template<typename FieldSchema, typename Encode, typename T, uint64_t D>
-void n_closest_add(saw::data<sch::Ptr<FieldSchema>,Encode>& f, const saw::data<sch::Vector<T,D>>& frac_ind, const saw::data<typename FieldSchema::InnerValueSchema>& val){
+void n_closest_add(const saw::data<sch::Ptr<FieldSchema>,Encode>& f, const saw::data<sch::Vector<T,D>>& frac_ind, const saw::data<typename FieldSchema::StoredValueSchema>& val){
 	auto shift_frac_ind = frac_ind;
 	for(uint64_t i{0u}; i < D; ++i){
 		
@@ -34,7 +37,14 @@ void n_closest_add(saw::data<sch::Ptr<FieldSchema>,Encode>& f, const saw::data<s
 		}
 	}
 
-	auto shift_ind = frac_ind.template cast_to<sch::UInt64>();
+	auto f_meta = f.meta();
+	saw::data<sch::FixedArray<sch::UInt64,D>> shift_ind;
+	for(uint64_t i{0u}; i < D; ++i){
+		shift_ind.at({i}) = frac_ind.at({{i}}).template cast_to<sch::UInt64>();
+		if(shift_ind.at({i}) < f_meta.at({i})){
+			shift_ind.at({i}) = f_meta.at({i}) - 1u;
+		}
+	}
 	auto& f_i = f.at(shift_ind);
 
 	f_i = f_i + val;
-- 
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