From eec5df246866a4a1008b37fef0a96d4be5fa9c79 Mon Sep 17 00:00:00 2001
From: "Claudius \"keldu\" Holeksa" <mail@keldu.de>
Date: Mon, 11 Aug 2025 18:21:59 +0200
Subject: End of day

---
 examples/poiseulle_particles_channel_2d.cpp | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/examples/poiseulle_particles_channel_2d.cpp b/examples/poiseulle_particles_channel_2d.cpp
index cfd4216..286b211 100644
--- a/examples/poiseulle_particles_channel_2d.cpp
+++ b/examples/poiseulle_particles_channel_2d.cpp
@@ -303,7 +303,7 @@ void add_particles(kel::lbm::particle_system<kel::lbm::sch::T,2u>& part_sys){
 		old_pos.at({{0u}}) = {32u};
 		old_pos.at({{1u}}) = {64u};
 
-		p_size = {4.0};
+		p_size = {1.0};
 	}
 
 	for(uint64_t i = 0; i < 60; ++i){
@@ -358,20 +358,34 @@ void couple_particles_to_lattice(
 				p_size * saw::data<sch::T>{std::cos(p_rot.get())}
 			}};
 
+			auto& p_mask_grid = p_mask.template get<"grid">();
+			// Get grid so we don't pull all the time
+			auto p_mask_grid_dims = p_mask_grid.dims();
+
+			saw::data<sch::Vector<sch::T,2u>> p_mask_grid_shift;
+			p_mask_grid_shift.at({{0u}}) = (p_mask_grid_dims.at({0u}).template cast_to<sch::T>() - 1.0) / 2.0;
+			p_mask_grid_shift.at({{1u}}) = (p_mask_grid_dims.at({1u}).template cast_to<sch::T>() - 1.0) / 2.0;
+
 			// Particle to Fluid Coupling
 			// Spread force to close fluid cells
 			iterate_over([&](const saw::data<sch::FixedArray<sch::UInt64,2u>>& index){
 				(void)index;
-			}, {{0u,0u}}, p_mask.template get<"grid">().dims());
+			}, {{0u,0u}}, p_mask_grid_dims);
 
 			// Fluid to Particle Coupling
 			// Prepare force sum
 			saw::data<sch::FixedArray<sch::T,2u>> forces;
 
 			iterate_over([&](const saw::data<sch::FixedArray<sch::UInt64,2u>>& index){
+
+				saw::data<sch::Vector<sch::T,2u>> index_shift;
+				index_shift.at({{0u}}) = index.at({0u}).template cast_to<sch::T>() - p_mask_grid_shift.at({{0u}});
+				index_shift.at({{1u}}) = index.at({0u}).template cast_to<sch::T>() - p_mask_grid_shift.at({{1u}});
+
+
 				saw::data<sch::Vector<sch::T,2u>> mask_shift;
-				mask_shift.at({{0u}}) = index.at({0u}).template cast_to<sch::T>() * x_dir.at({0u}) + index.at({1u}).template cast_to<sch::T>() * y_dir.at({0u});
-				mask_shift.at({{1u}}) = index.at({0u}).template cast_to<sch::T>() * x_dir.at({1u}) + index.at({1u}).template cast_to<sch::T>() * y_dir.at({1u});
+				mask_shift.at({{0u}}) = index_shift.at({{0u}}) * x_dir.at({0u}) + index_shift.at({{1u}}) * y_dir.at({0u});
+				mask_shift.at({{1u}}) = index_shift.at({{0u}}) * x_dir.at({1u}) + index_shift.at({{1u}}) * y_dir.at({1u});
 
 				auto p_pos_lie = p_pos + mask_shift;
 
@@ -407,7 +421,7 @@ void couple_particles_to_lattice(
 
 				// Add forces to push away from other particles
 
-			}, {{0u,0u}}, p_mask.template get<"grid">().dims());
+			}, {{0u,0u}}, p_mask_grid.dims());
 
 			p_acc.at({{0u}}).set(p_acc.at({{0u}}).get() / (p_mask.template get<"grid">().dims().at({{0u}}).get() *p_mask.template get<"grid">().dims().at({{1u}}).get() ));
 			p_acc.at({{1u}}).set(p_acc.at({{1u}}).get() / (p_mask.template get<"grid">().dims().at({{0u}}).get() *p_mask.template get<"grid">().dims().at({{1u}}).get() ));
@@ -427,7 +441,7 @@ void lbm_step(
 	*/
 	component<sch::T, sch::D2Q9, cmpt::BGK> coll{0.5384};
 	component<sch::T, sch::D2Q9, cmpt::BounceBack> bb;
-	component<sch::T, sch::D2Q9, cmpt::PressureBoundaryRestrictedVelocityTo<true>> inlet{1.01 * dfi::cs2};
+	component<sch::T, sch::D2Q9, cmpt::PressureBoundaryRestrictedVelocityTo<true>> inlet{1.1 * dfi::cs2 * 2.0 / 3.0};
 	component<sch::T, sch::D2Q9, cmpt::PressureBoundaryRestrictedVelocityTo<false>> outlet{1.0 * dfi::cs2 * 2.0 / 3.0};
 
 	auto meta = latt.meta();
@@ -559,7 +573,7 @@ int main(int argc, char** argv){
 
 	saw::data<sch::Array<sch::MacroStruct<sch::T,sch::D2Q9::D>,sch::D2Q9::D>> macros{dim};
 
-	for(uint64_t i = 0u; i < 1024u; ++i){
+	for(uint64_t i = 0u; i < 4096u*4u; ++i){
 		bool even_step = ((i % 2u) == 0u);
 
 		{
-- 
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