From d9c7b84f757c8e2935eddce74c095a8448b99c55 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Fri, 7 Nov 2025 15:45:14 +0100
Subject: Adding ptr based access

---
 lib/core/c++/boundary.hpp  | 22 ++++++++++++++++++++++
 lib/core/c++/collision.hpp | 22 ++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/lib/core/c++/boundary.hpp b/lib/core/c++/boundary.hpp
index c10784c..5549a80 100644
--- a/lib/core/c++/boundary.hpp
+++ b/lib/core/c++/boundary.hpp
@@ -62,6 +62,28 @@ public:
 			dfs_old({i}) = df_cpy({dfi::opposite_index.at(i)});
 		}
 	}
+	
+	template<typename CellStructSchema>
+	void apply(
+		saw::data<CellStructSchema, Encode>* field, 
+		const saw::data<sch::FixedArray<sch::UInt64,Descriptor::D>>& meta,
+		const saw::data<sch::FixedArray<sch::UInt64,Descriptor::D>>& index,
+		saw::data<sch::UInt64> time_step
+	){
+		bool is_even = ((time_step.get() % 2) == 0);
+		auto& cell = field[0u];
+		
+		auto& dfs_old = (is_even) ? cell.template get<"dfs_old">() : cell.template get<"dfs">();
+
+		saw::data<T> rho;
+		saw::data<sch::FixedArray<T,Descriptor::D>> vel;
+		compute_rho_u<T,Descriptor>(dfs_old,rho,vel);
+		auto eq = equilibrium<T,Descriptor>(rho,vel);
+
+		for(uint64_t i = 0u; i < Descriptor::Q; ++i){
+			dfs_old({i}) = dfs_old({i}) + frequency_ * (eq.at(i) - dfs_old({i}));
+		}
+	}
 };
 
 /**
diff --git a/lib/core/c++/collision.hpp b/lib/core/c++/collision.hpp
index 73e86ae..2f20601 100644
--- a/lib/core/c++/collision.hpp
+++ b/lib/core/c++/collision.hpp
@@ -62,6 +62,28 @@ public:
 			// dfs_old({i}).set(dfs_old({i}).get() + (1.0 / relaxation_) * (eq.at(i).get() - dfs_old({i}).get()));
 		}
 	}
+
+	template<typename CellStructSchema>
+	void apply(
+		saw::data<CellStructSchema, Encode>* field, 
+		const saw::data<sch::FixedArray<sch::UInt64,Descriptor::D>>& meta,
+		const saw::data<sch::FixedArray<sch::UInt64,Descriptor::D>>& index,
+		saw::data<sch::UInt64> time_step
+	){
+		bool is_even = ((time_step.get() % 2) == 0);
+		auto& cell = field[0u];
+		
+		auto& dfs_old = (is_even) ? cell.template get<"dfs_old">() : cell.template get<"dfs">();
+
+		saw::data<T> rho;
+		saw::data<sch::FixedArray<T,Descriptor::D>> vel;
+		compute_rho_u<T,Descriptor>(dfs_old,rho,vel);
+		auto eq = equilibrium<T,Descriptor>(rho,vel);
+
+		for(uint64_t i = 0u; i < Descriptor::Q; ++i){
+			dfs_old({i}) = dfs_old({i}) + frequency_ * (eq.at(i) - dfs_old({i}));
+		}
+	}
 };
 
 template<typename T, typename Descriptor, typename Encode>
-- 
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