Final run

12 files changed, 185 insertions, 130 deletions

diff --git a/default.nix b/default.nix
index 02f9213..cc87f20 100644
--- a/default.nix
+++ b/default.nix
@@ -46,7 +46,7 @@ let
 
 		 src = builtins.fetchurl {
 			url = "https://git.keldu.de/forstio-forstio/snapshot/master.tar.gz";
-			sha256 = "sha256:15iqzmymza47jjx4wpc19mbg3zzwmkabpssf5y968f566n0fnb9a";
+			sha256 = "sha256:0jg8a057zqqniv4cmwq0v7xmh42bn5vsjwyvpswpf9r3p5fpgxhb";
 		 };
 
 		 phases = [ "unpackPhase" "installPhase" ];
diff --git a/examples/poiseulle_particles_2d_bgk_gpu/sim.cpp b/examples/poiseulle_particles_2d_bgk_gpu/sim.cpp
index 73964b7..ef4639e 100644
--- a/examples/poiseulle_particles_2d_bgk_gpu/sim.cpp
+++ b/examples/poiseulle_particles_2d_bgk_gpu/sim.cpp
@@ -171,7 +171,7 @@ saw::error_or<void> step(
 	// auto coll_ev = 
 	q.submit([&](acpp::sycl::handler& h){
 		// Need nicer things to handle the flow. I see improvement here
-		component<T,Desc,cmpt::BGK, encode::Sycl<saw::encode::Native>> collision{0.65};
+		component<T,Desc,cmpt::BGK, encode::Sycl<saw::encode::Native>> collision{0.8};
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
 
diff --git a/examples/poiseulle_particles_2d_fplbm_gpu/sim.cpp b/examples/poiseulle_particles_2d_fplbm_gpu/sim.cpp
index 93d4b46..3d16884 100644
--- a/examples/poiseulle_particles_2d_fplbm_gpu/sim.cpp
+++ b/examples/poiseulle_particles_2d_fplbm_gpu/sim.cpp
@@ -51,6 +51,7 @@ template<typename T, typename Desc>
 using MacroStruct = Struct<
 	Member<VelChunk<T,Desc>, "velocity">,
 	Member<RhoChunk<T>, "density">,
+	Member<VelChunk<T,Desc>, "force">,
 	Member<ScalarChunk<T,Desc>, "porosity">
 >;
 
@@ -144,6 +145,7 @@ saw::error_or<void> setup_initial_conditions(
 		{{1u,1u}}
 	);
 
+	/*
 	iterator<Desc::D>::apply(
 		[&](auto& index){
 			saw::data<sch::Vector<T,Desc::D>> middle, ind_vec;
@@ -162,6 +164,7 @@ saw::error_or<void> setup_initial_conditions(
 		{},// 0-index
 		df_f.get_dims()
 	);
+	*/
 
 	return saw::make_void();
 }
@@ -179,16 +182,20 @@ saw::error_or<void> step(
 
 	// auto coll_ev =
 	q.submit([&](acpp::sycl::handler& h){
-		component<T,Desc,cmpt::FpLbmOneParticleNoVelocity,encode::Sycl<saw::encode::Native>> collision{0.65};
+		component<T,Desc,cmpt::BGK, encode::Sycl<saw::encode::Native>> bgk{0.8};
+		component<T,Desc,cmpt::FpLbmOneParticleNoVelocity,encode::Sycl<saw::encode::Native>> collision{0.8};
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
-		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
-
-		saw::data<sch::Scalar<T>> rho_b;
-		rho_b.at({}) = 1.0;
-		saw::data<sch::Vector<T,Desc::D>> vel_b;
-		vel_b.at({{0u}}) = 0.015;
 
-		component<T,Desc,cmpt::Equilibrium,encode::Sycl<saw::encode::Native>> equi{rho_b,vel_b};
+		saw::data<sch::Scalar<T>> eps;
+		eps.at({}).set(1.5f);
+		saw::data<sch::Scalar<T>> rad;
+		rad.at({}).set(dim_y*0.1);
+		saw::data<sch::Vector<T,Desc::D>> p_pos;
+		{
+			p_pos.at({{0u}}) = dim_x * 0.25;
+			p_pos.at({{1u}}) = dim_y * 0.5;
+		}
+		component<T,Desc,cmpt::OneParticleAt,encode::Sycl<saw::encode::Native>> opa{p_pos,rad,eps};
 
 		component<T,Desc,cmpt::ZouHeHorizontal<true>,encode::Sycl<saw::encode::Native>> flow_in{
 			[&](){
@@ -217,17 +224,18 @@ saw::error_or<void> step(
 					bb.apply(fields,index,t_i);
 				break;
 				case 2u:
+					opa.apply(macros,index,t_i);
 					collision.apply(fields,macros,index,t_i);
 					break;
 				case 3u:
 					flow_in.apply(fields,index,t_i);
 					// equi.apply(fields,index,t_i);
-					collision.apply(fields,macros,index,t_i);
+					bgk.apply(fields,macros,index,t_i);
 					break;
 				case 4u:
 					flow_out.apply(fields,index,t_i);
 					// equi.apply(fields,index,t_i);
-					collision.apply(fields,macros,index,t_i);
+					bgk.apply(fields,macros,index,t_i);
 				break;
 				default:
 				break;
@@ -349,20 +357,7 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			}
 		}
 		sycl_q.wait();
-		if(i.get() % 32u == 0u){
-			{
-				auto eov = dev.copy_to_host(lbm_sycl_macro_data,*lbm_macro_data_ptr);
-				if(eov.is_error()){
-					return eov;
-				}
-			}
-			{
-				auto eov = write_csv_file(out_dir,"m",i.get(), *lbm_macro_data_ptr);
-				if(eov.is_error()){
-					return eov;
-				}
-			}
-		}
+
 		// Stream
 		sycl_q.submit([&](acpp::sycl::handler& h){
 			component<T,Desc,cmpt::Stream,encode::Sycl<saw::encode::Native>> stream;
@@ -402,6 +397,12 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			return eov;
 		}
 	}
+	{
+		auto eov = write_csv_file(out_dir,"m",time_steps.get(), *lbm_macro_data_ptr);
+		if(eov.is_error()){
+			return eov;
+		}
+	}
 
 	sycl_q.wait();
 	return saw::make_void();
diff --git a/examples/poiseulle_particles_2d_hlbm_gpu/sim.cpp b/examples/poiseulle_particles_2d_hlbm_gpu/sim.cpp
index b09aa64..b1bd37d 100644
--- a/examples/poiseulle_particles_2d_hlbm_gpu/sim.cpp
+++ b/examples/poiseulle_particles_2d_hlbm_gpu/sim.cpp
@@ -48,6 +48,7 @@ template<typename T, typename Desc>
 using MacroStruct = Struct<
 	Member<VelChunk<T,Desc>, "velocity">,
 	Member<RhoChunk<T>, "density">,
+	Member<VelChunk<T,Desc>, "force">,
 	Member<ScalarChunk<T,Desc>, "porosity">
 >;
 
@@ -140,7 +141,8 @@ saw::error_or<void> setup_initial_conditions(
 		df_f.get_dims(),
 		{{1u,1u}}
 	);
-	
+
+	/*
 	iterator<Desc::D>::apply(
 		[&](auto& index){
 			saw::data<sch::Vector<T,Desc::D>> middle, ind_vec;
@@ -159,6 +161,7 @@ saw::error_or<void> setup_initial_conditions(
 		{},// 0-index
 		df_f.get_dims()
 	);
+	*/
 
 	return saw::make_void();
 }
@@ -176,16 +179,23 @@ saw::error_or<void> step(
 
 	// auto coll_ev = 
 	q.submit([&](acpp::sycl::handler& h){
-		component<T,Desc,cmpt::Hlbm,encode::Sycl<saw::encode::Native>> collision{0.65};
+		component<T,Desc,cmpt::BGK, encode::Sycl<saw::encode::Native>> bgk{0.8};
+		component<T,Desc,cmpt::Hlbm,encode::Sycl<saw::encode::Native>> collision{0.8};
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
 
-		saw::data<sch::Scalar<T>> rho_b;
-		rho_b.at({}) = 1.0;
-		saw::data<sch::Vector<T,Desc::D>> vel_b;
-		vel_b.at({{0u}}) = 0.015;
-
-		component<T,Desc,cmpt::Equilibrium,encode::Sycl<saw::encode::Native>> equi{rho_b,vel_b};
+		saw::data<sch::Scalar<T>> eps;
+		eps.at({}).set(1.5f);
+		saw::data<sch::Scalar<T>> rad;
+		rad.at({}).set(dim_y*0.1);
+		saw::data<sch::Vector<T,Desc::D>> p_pos;
+		{
+			p_pos.at({{0u}}) = dim_x * 0.25;
+			p_pos.at({{1u}}) = dim_y * 0.5;
+		}
+		component<T,Desc,cmpt::OneParticleAt,encode::Sycl<saw::encode::Native>> opa{p_pos,rad,eps};
+		
+		component<T,Desc,cmpt::ForceGather, encode::Sycl<saw::encode::Native>> fg;
 
 		component<T,Desc,cmpt::ZouHeHorizontal<true>,encode::Sycl<saw::encode::Native>> flow_in{
 			[&](){
@@ -214,32 +224,19 @@ saw::error_or<void> step(
 					bb.apply(fields,index,t_i);
 				break;
 				case 2u:
+					opa.apply(macros,index,t_i);
 					collision.apply(fields,macros,index,t_i);
-					{
-						saw::data<sch::Vector<T,Desc::D>> middle;
-						middle.at({{0u}}) = dim_x * 0.25;
-						middle.at({{1u}}) = dim_y * 0.5;
-
-						saw::data<sch::Vector<T,Desc::D>> ind_vec;
-						ind_vec.at({{0u}}) = index.at({{0u}}).template cast_to<T>();
-						ind_vec.at({{1u}}) = index.at({{1u}}).template cast_to<T>();
-
-						auto dist = middle - ind_vec;
-						auto dist_2 = saw::math::dot(dist,dist);
-						if(dist_2.at({}).get() < dim_y*dim_y*0.01){
-							porous_f.at(index).at({}) = 0.0;
-						}
-					}
+					fg.apply(fields,macros,index,t_i);
 					break;
 				case 3u:
 					flow_in.apply(fields,index,t_i);
 					// equi.apply(fields,index,t_i);
-					collision.apply(fields,macros,index,t_i);
+					bgk.apply(fields,macros,index,t_i);
 					break;
 				case 4u:
 					flow_out.apply(fields,index,t_i);
 					// equi.apply(fields,index,t_i);
-					collision.apply(fields,macros,index,t_i);
+					bgk.apply(fields,macros,index,t_i);
 				break;
 				default:
 				break;
diff --git a/examples/poiseulle_particles_2d_psm_gpu/sim.cpp b/examples/poiseulle_particles_2d_psm_gpu/sim.cpp
index b3ea7ae..7d3c6f5 100644
--- a/examples/poiseulle_particles_2d_psm_gpu/sim.cpp
+++ b/examples/poiseulle_particles_2d_psm_gpu/sim.cpp
@@ -49,6 +49,7 @@ template<typename T, typename Desc>
 using MacroStruct = Struct<
 	Member<VelChunk<T,Desc>, "velocity">,
 	Member<RhoChunk<T>, "density">,
+	Member<VelChunk<T,Desc>, "force">,
 	Member<ScalarChunk<T,Desc>, "porosity">
 >;
 
@@ -216,17 +217,9 @@ saw::error_or<void> step(
 	auto& porous_f = macros.template get<"porosity">();
 
 	q.submit([&](acpp::sycl::handler& h){
+		component<T,Desc,cmpt::BGK, encode::Sycl<saw::encode::Native>> bgk{0.8};
 		component<T,Desc,cmpt::PSM,encode::Sycl<saw::encode::Native>> collision{0.8};
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
-		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
-
-		saw::data<sch::Scalar<T>> rho_b;
-		rho_b.at({}) = 1.0;
-		saw::data<sch::Vector<T,Desc::D>> vel_b;
-		vel_b.at({{0u}}) = 0.015;
-
-		component<T,Desc,cmpt::Equilibrium,encode::Sycl<saw::encode::Native>> equi{rho_b,vel_b};
-
 
 		saw::data<sch::Scalar<T>> eps;
 		eps.at({}).set(1.5f);
@@ -250,6 +243,7 @@ saw::error_or<void> step(
 		};
 		component<T,Desc,cmpt::ZouHeHorizontal<false>,encode::Sycl<saw::encode::Native>> flow_out{1.0};
 
+		component<T,Desc,cmpt::ForceGather, encode::Sycl<saw::encode::Native>> fg;
 
 		h.parallel_for(acpp::sycl::range<Desc::D>{dim_x,dim_y}, [=](acpp::sycl::id<Desc::D> idx){
 			saw::data<sch::FixedArray<sch::UInt64,Desc::D>> index;
@@ -268,16 +262,17 @@ saw::error_or<void> step(
 				case 2u:
 					opa.apply(macros,index,t_i);
 					collision.apply(fields,macros,index,t_i);
+					fg.apply(fields,macros,index,t_i);
 					break;
 				case 3u:
 					flow_in.apply(fields,index,t_i);
 					//equi.apply(fields,index,t_i);
-					collision.apply(fields,macros,index,t_i);
+					bgk.apply(fields,macros,index,t_i);
 					break;
 				case 4u:
 					flow_out.apply(fields,index,t_i);
 					// equi.apply(fields,index,t_i);
-					collision.apply(fields,macros,index,t_i);
+					bgk.apply(fields,macros,index,t_i);
 					break;
 				case 5u:
 					// Corners
diff --git a/examples/stokes_drag_particle_2d_hlbm_gpu/sim.cpp b/examples/stokes_drag_particle_2d_hlbm_gpu/sim.cpp
index a8ba21f..81498e2 100644
--- a/examples/stokes_drag_particle_2d_hlbm_gpu/sim.cpp
+++ b/examples/stokes_drag_particle_2d_hlbm_gpu/sim.cpp
@@ -13,7 +13,7 @@ namespace lbm {
 constexpr uint64_t dim_y = 1024ul;
 constexpr uint64_t dim_x = dim_y * 2ul;
 
-constexpr uint64_t particle_amount = 1ul;
+// constexpr uint64_t particle_amount = 1ul;
 
 namespace sch {
 using namespace saw::schema;
@@ -47,6 +47,7 @@ using RhoChunk = Chunk<Scalar<T>, 0u, dim_x, dim_y>;
 template<typename T, typename Desc>
 using MacroStruct = Struct<
 	Member<VelChunk<T,Desc>, "velocity">,
+	Member<VelChunk<T,Desc>, "force">,
 	Member<RhoChunk<T>, "density">,
 	Member<ScalarChunk<T,Desc>, "porosity">
 >;
@@ -158,25 +159,6 @@ saw::error_or<void> setup_initial_conditions(
 		{{1u,1u}}
 	);
 	
-	iterator<Desc::D>::apply(
-		[&](auto& index){
-			saw::data<sch::Vector<T,Desc::D>> middle, ind_vec;
-			middle.at({{0u}}) = dim_x * 0.5;
-			middle.at({{1u}}) = dim_y * 0.5;
-
-			ind_vec.at({{0u}}) = index.at({{0u}}).template cast_to<T>();
-			ind_vec.at({{1u}}) = index.at({{1u}}).template cast_to<T>();
-
-			auto dist = middle - ind_vec;
-			auto dist_2 = saw::math::dot(dist,dist);
-			if(dist_2.at({}).get() < dim_y*dim_y*0.01){
-				porous_f.at(index).at({}) = 0.0;
-			}
-		},
-		{},// 0-index
-		df_f.get_dims()
-	);
-
 	return saw::make_void();
 }
 
@@ -196,12 +178,16 @@ saw::error_or<void> step(
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
 
-		saw::data<sch::Scalar<T>> rho_b;
-		rho_b.at({}) = 1.0;
-		saw::data<sch::Vector<T,Desc::D>> vel_b;
-		vel_b.at({{0u}}) = 0.015;
-
-		component<T,Desc,cmpt::Equilibrium,encode::Sycl<saw::encode::Native>> equi{rho_b,vel_b};
+		saw::data<sch::Scalar<T>> eps;
+		eps.at({}).set(1.5f);
+		saw::data<sch::Scalar<T>> rad;
+		rad.at({}).set(dim_y*0.1*0.25);
+		saw::data<sch::Vector<T,Desc::D>> p_pos;
+		{
+			p_pos.at({{0u}}) = dim_x * 0.5;
+			p_pos.at({{1u}}) = dim_y * 0.5;
+		}
+		component<T,Desc,cmpt::OneParticleAt,encode::Sycl<saw::encode::Native>> opa{p_pos,rad,eps};
 
 		component<T,Desc,cmpt::ZouHeHorizontal<true>,encode::Sycl<saw::encode::Native>> flow_in{
 			[&](){
@@ -230,6 +216,7 @@ saw::error_or<void> step(
 					abb.apply(fields,index,t_i);
 				break;
 				case 2u:
+					opa.apply(macros,index,t_i);
 					collision.apply(fields,macros,index,t_i);
 					break;
 				case 3u:
@@ -385,20 +372,7 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			}
 		}
 		*/
-		if(i.get() % 32u == 0u){
-			{
-				auto eov = dev.copy_to_host(lbm_sycl_macro_data,*lbm_macro_data_ptr);
-				if(eov.is_error()){
-					return eov;
-				}
-			}
-			{
-				auto eov = write_csv_file(out_dir,"m",i.get(), *lbm_macro_data_ptr);
-				if(eov.is_error()){
-					return eov;
-				}
-			}
-		}
+
 		// Stream
 		sycl_q.submit([&](acpp::sycl::handler& h){
 			component<T,Desc,cmpt::Stream,encode::Sycl<saw::encode::Native>> stream;
@@ -438,6 +412,12 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			return eov;
 		}
 	}
+	{
+		auto eov = write_csv_file(out_dir,"m",time_steps.get(), *lbm_macro_data_ptr);
+		if(eov.is_error()){
+			return eov;
+		}
+	}
 
 	sycl_q.wait();
 	return saw::make_void();
diff --git a/examples/stokes_drag_particle_2d_psm_gpu/sim.cpp b/examples/stokes_drag_particle_2d_psm_gpu/sim.cpp
index 0ff6e6b..6942cc7 100644
--- a/examples/stokes_drag_particle_2d_psm_gpu/sim.cpp
+++ b/examples/stokes_drag_particle_2d_psm_gpu/sim.cpp
@@ -48,6 +48,7 @@ template<typename T, typename Desc>
 using MacroStruct = Struct<
 	Member<VelChunk<T,Desc>, "velocity">,
 	Member<RhoChunk<T>, "density">,
+	Member<VelChunk<T,Desc>, "force">,
 	Member<ScalarChunk<T,Desc>, "porosity">
 >;
 
@@ -196,12 +197,16 @@ saw::error_or<void> step(
 		component<T,Desc,cmpt::BounceBack,encode::Sycl<saw::encode::Native>> bb;
 		component<T,Desc,cmpt::AntiBounceBack<0u>,encode::Sycl<saw::encode::Native>> abb;
 
-		saw::data<sch::Scalar<T>> rho_b;
-		rho_b.at({}) = 1.0;
-		saw::data<sch::Vector<T,Desc::D>> vel_b;
-		vel_b.at({{0u}}) = 0.015;
-
-		component<T,Desc,cmpt::Equilibrium,encode::Sycl<saw::encode::Native>> equi{rho_b,vel_b};
+		saw::data<sch::Scalar<T>> eps;
+		eps.at({}).set(1.5f);
+		saw::data<sch::Scalar<T>> rad;
+		rad.at({}).set(dim_y*0.1*0.25);
+		saw::data<sch::Vector<T,Desc::D>> p_pos;
+		{
+			p_pos.at({{0u}}) = dim_x * 0.5;
+			p_pos.at({{1u}}) = dim_y * 0.5;
+		}
+		component<T,Desc,cmpt::OneParticleAt,encode::Sycl<saw::encode::Native>> opa{p_pos,rad,eps};
 
 		component<T,Desc,cmpt::ZouHeHorizontal<true>,encode::Sycl<saw::encode::Native>> flow_in{
 			[&](){
@@ -230,6 +235,7 @@ saw::error_or<void> step(
 					abb.apply(fields,index,t_i);
 				break;
 				case 2u:
+					opa.apply(macros,index,t_i);
 					collision.apply(fields,macros,index,t_i);
 					break;
 				case 3u:
@@ -385,20 +391,6 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			}
 		}
 		*/
-		if(i.get() % 32u == 0u){
-			{
-				auto eov = dev.copy_to_host(lbm_sycl_macro_data,*lbm_macro_data_ptr);
-				if(eov.is_error()){
-					return eov;
-				}
-			}
-			{
-				auto eov = write_csv_file(out_dir,"m",i.get(), *lbm_macro_data_ptr);
-				if(eov.is_error()){
-					return eov;
-				}
-			}
-		}
 		// Stream
 		sycl_q.submit([&](acpp::sycl::handler& h){
 			component<T,Desc,cmpt::Stream,encode::Sycl<saw::encode::Native>> stream;
@@ -438,7 +430,12 @@ saw::error_or<void> lbm_main(int argc, char** argv){
 			return eov;
 		}
 	}
-
+	{
+		auto eov = write_csv_file(out_dir,"m",time_steps.get(), *lbm_macro_data_ptr);
+		if(eov.is_error()){
+			return eov;
+		}
+	}
 	sycl_q.wait();
 	return saw::make_void();
 }
diff --git a/lib/core/c++/fplbm.hpp b/lib/core/c++/fplbm.hpp
index 61def6b..c974472 100644
--- a/lib/core/c++/fplbm.hpp
+++ b/lib/core/c++/fplbm.hpp
@@ -114,6 +114,19 @@ public:
 		auto& vel_f = macros.template get<"velocity">();
 		auto& por_f = macros.template get<"porosity">();
 
+		// Temporary find a better way
+		auto& force_f = macros.template get<"force">();
+
+
+		/**
+		 * The other methods all work with a flipped porosity.
+		 * For compat reasons this is also flipped
+		 */
+		auto porosity = por_f.at(index);
+		saw::data<sch::Scalar<T>> one;
+		one.at({}) = 1.0;
+		auto flip_porosity = one - porosity;
+
 		saw::data<sch::Scalar<T>>& rho = rho_f.at(index);
 
 		saw::data<sch::Scalar<T>> half;
@@ -128,12 +141,13 @@ public:
 		saw::data<sch::Scalar<T>> min_two;
 		min_two.at({}).set(-2);
 
-		auto force = vel * rho * min_two * por_f.at(index);
+		// Maybe ? 
+		auto& force = force_f.at(index);
+		force = vel * rho * min_two * flip_porosity;
 
 		saw::data<sch::Scalar<T>> dfi_inv_cs2;
 		dfi_inv_cs2.at({}).set(dfi::inv_cs2);
 
-
 		// auto vel = vel_f.at(index);
 
 		for(uint64_t i = 0u; i < Descriptor::Q; ++i){
diff --git a/lib/core/c++/lbm.hpp b/lib/core/c++/lbm.hpp
index b34ec10..23d30b1 100644
--- a/lib/core/c++/lbm.hpp
+++ b/lib/core/c++/lbm.hpp
@@ -16,6 +16,7 @@
 #include "iterator.hpp"
 #include "hlbm.hpp"
 #include "macroscopic.hpp"
+#include "momentum_gather.hpp"
 #include "memory.hpp"
 #include "psm.hpp"
 #include "stream.hpp"
diff --git a/lib/core/c++/momentum_gather.hpp b/lib/core/c++/momentum_gather.hpp
new file mode 100644
index 0000000..7b1fc96
--- /dev/null
+++ b/lib/core/c++/momentum_gather.hpp
@@ -0,0 +1,54 @@
+#pragma once
+
+#include "common.hpp"
+#include "macroscopic.hpp"
+#include "component.hpp"
+#include "equilibrium.hpp"
+
+namespace kel {
+namespace lbm {
+namespace cmpt {
+// Gather the force, Luke!
+struct ForceGather {};
+}
+
+template<typename T, typename Descriptor, typename Encode>
+class component<T,Descriptor,cmpt::ForceGather, Encode> {
+private:
+public:
+	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_f = macros.template get<"porosity">();
+		auto& porous = porous_f.at(index);
+
+		auto& force_f = macros.template get<"force">();
+		auto& force = force_f.at(index);
+
+		for(uint64_t k{0u}; k < Descriptor::D; ++k){
+			force.at({{k}}).set(0);
+		}
+
+		auto& dfs = dfs_old_f.at(index);
+		for(uint64_t i{0u}; i < Descriptor::Q; ++i){
+			uint64_t i_opp = dfi::opposite_index[i];
+			auto dfs_diff = dfs.at({i}) - dfs.at({i_opp});
+			for(uint64_t k{0u}; k < Descriptor::D; ++k){
+				force.at({{k}}) = force.at({{k}}) + dfs_diff * saw::data<T>{dfi::directions[i][k]};
+			}
+		}
+
+		saw::data<sch::Scalar<T>> one;
+		one.at({}) = 1.0;
+		auto flip_porous = one - porous;
+		force = force * flip_porous;
+	}
+};
+}
+}
diff --git a/lib/core/c++/particle/porosity.hpp b/lib/core/c++/particle/porosity.hpp
index 11185c5..2f39d2e 100644
--- a/lib/core/c++/particle/porosity.hpp
+++ b/lib/core/c++/particle/porosity.hpp
@@ -48,17 +48,17 @@ public:
 		auto rad_high = rad + eps_h;
 
 		if(s_dist.at({}) <= rad_low.at({})){
-			por.at({}).set(1);
+			por.at({}).set(0);
 			return por;
 		}
 		if(s_dist.at({}) >= rad_high.at({})){
-			por.at({}).set(0);
+			por.at({}).set(1);
 			return por;
 		}
 
 		{
-			typename saw::native_data_type<T>::type inner = (std::numbers::pi / ( eps.at({}).get() )) * (s_dist - rad_low).at({}).get();
-			auto cos_inner = std::cos(inner);
+			typename saw::native_data_type<T>::type inner = (std::numbers::pi / ( 2 * eps.at({}).get() )) * (s_dist - rad_low).at({}).get();
+			auto cos_inner = std::sin(inner);
 			auto cos_i_2 = cos_inner * cos_inner;
 			por.at({}).set(cos_i_2);
 		}
diff --git a/lib/core/c++/psm.hpp b/lib/core/c++/psm.hpp
index 3bd3520..6dc146f 100644
--- a/lib/core/c++/psm.hpp
+++ b/lib/core/c++/psm.hpp
@@ -40,7 +40,7 @@ public:
 
 		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);
 
@@ -60,6 +60,22 @@ public:
 			uint64_t i_opp = dfi::opposite_index[i];
 			dfs.at({i}) = dfs_cpy.at({i}) + frequency_ * (eq.at(i) - dfs_cpy.at({i})) * porous.at({}) + (dfs_cpy.at({i_opp}) - dfs_cpy.at({i}) ) * flip_porous;
 		}
+
+		auto& force_f = macros.template get<"force">();
+		auto& force = force_f.at(index);
+		for(uint64_t k{0u}; k < Descriptor::D; ++k){
+			force.at({{k}}).set(0);
+		}
+
+		for(uint64_t i{0u}; i < Descriptor::Q; ++i){
+			uint64_t i_opp = dfi::opposite_index[i];
+			auto dfs_diff = dfs.at({i}) - dfs.at({i_opp});
+			for(uint64_t k{0u}; k < Descriptor::D; ++k){
+				force.at({{k}}) = force.at({{k}}) + dfs_diff;
+			}
+		}
+
+		force = force * porous;
 	}
 };