From dc1c481df599550fd5717790d908a3879f62960a Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Fri, 20 Feb 2026 10:53:05 +0100
Subject: Fixing Guo forcing problems

---
 lib/core/c++/psm.hpp | 39 +++++++++++++++++++++++++++++++++++----
 1 file changed, 35 insertions(+), 4 deletions(-)

(limited to 'lib/core/c++/psm.hpp')

diff --git a/lib/core/c++/psm.hpp b/lib/core/c++/psm.hpp
index 8e151c3..94d5ccd 100644
--- a/lib/core/c++/psm.hpp
+++ b/lib/core/c++/psm.hpp
@@ -11,23 +11,54 @@ struct PSM {};
 }
 
 /**
- * HLBM collision operator for LBM
+ * PSM collision operator for LBM
  */
 template<typename T, typename Descriptor, typename Encode>
 class component<T, Descriptor, cmpt::PSM> {
 private:
+	saw::data<sch::Scalar<T>> relaxation_;
+	saw::data<sch::Scalar<T>> frequency_;
 public:
-	component() = default;
+	component(
+		saw::data<sch::Scalar<T>> relaxation__
+	):
+		relaxation_{relaxation__}
+	{
+		saw::data<sch::Scalar<T>> one;
+		frequency_ = one / relaxation_;
+	}
 
 	template<typename CellFieldSchema, typename MacroFieldSchema>
 	void apply(const saw::data<CellFieldSchema, Encode>& field, const saw::data<MacroFieldSchema,Encode>& macros, saw::data<sch::FixedArray<sch::UInt64,Descriptor::D>> index, saw::data<sch::UInt64> time_step) const {
-		
+	
+		using dfi = df_info<T,Descriptor>;
 		bool is_even = ((time_step.get() % 2) == 0);
 
 		auto& dfs_old_f = (is_even) ? field.template get<"dfs_old">() : field.template get<"dfs">();
 		auto& porous = field.template get<"porosity">();
 
-				
+		auto& rho_f = macros.template get<"density">();
+		auto& vel_f = macros.template get<"velocity">();
+	
+		saw::data<sch::Scalar<T>>& rho = rho_f.at(index);
+		saw::data<sch::Vector<T,Descriptor::D>>& vel = vel_f.at(index);
+
+		compute_rho_u<T,Descriptor>(dfs_old_f.at(index),rho,vel);
+		
+		auto eq = equilibrium<T,Descriptor>(rho,vel);
+
+		saw::data<sch::Scalar<T>> one;
+		one.at({}) = 1.0;
+		auto flip_porous = one - porous;
+
+		auto& dfs = dfs_old_f.at(index);
+
+		auto dfs_cpy = dfs;
+
+		for(uint64_t i = 0u; i < Descriptor::Q; ++i){
+			uint64_t i_opp = dfi::opposite_index[i];
+			dfs.at({i}) = dfs_cpy.at({i}) + frequency_ * (eq.at(i) - dfs_cpy.at({i})) * flip_porous + (dfs_cpy.at({i_opp}) - dfs_cpy.at({i}) ) * porous;
+		}
 	}
 };
 
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