DummyParticles with ContinuityDensity on GPU is broken (#870)

* Bug not GPU compatible setter

* add test

* format

* Update dam_break_2d_gpu.jl

Author: svchb

examples/fluid/dam_break_2d_gpu.jl

@@ -40,4 +40,5 @@ trixi_include(@__MODULE__,
               density_diffusion=density_diffusion,
               boundary_layers=boundary_layers, spacing_ratio=spacing_ratio,
               boundary_model=boundary_model,
-              parallelization_backend=PolyesterBackend())
+              parallelization_backend=PolyesterBackend(),
+              boundary_density_calculator=boundary_density_calculator)

src/schemes/boundary/system.jl

@@ -384,10 +384,7 @@ function write_v0!(v0,
     (; cache) = system.boundary_model
     (; initial_density) = cache
 
-    for particle in eachparticle(system)
-        # Set particle densities
-        v0[1, particle] = initial_density[particle]
-    end
+    v0[1, :] = initial_density
 
     return v0
 end

test/examples/gpu.jl

@@ -87,6 +87,23 @@ end
             end
         end
 
+        @trixi_testset "fluid/dam_break_2d_gpu.jl Float32 with ContinuityDensity boundary density" begin
+            @trixi_test_nowarn trixi_include_changeprecision(Float32, @__MODULE__,
+                                                             joinpath(examples_dir(),
+                                                                      "fluid",
+                                                                      "dam_break_2d_gpu.jl");
+                                                             tspan=(0.0f0, 0.1f0),
+                                                             parallelization_backend=Main.parallelization_backend,
+                                                             boundary_density_calculator=ContinuityDensity()) [
+                r"┌ Info: The desired tank length in y-direction .*\n",
+                r"└ New tank length in y-direction.*\n"
+            ]
+            @test semi.neighborhood_searches[1][1].cell_list isa FullGridCellList
+            @test sol.retcode == ReturnCode.Success
+            backend = TrixiParticles.KernelAbstractions.get_backend(sol.u[end].x[1])
+            @test backend == Main.parallelization_backend
+        end
+
         @trixi_testset "fluid/dam_break_2d_gpu.jl Float32 BoundaryModelMonaghanKajtar" begin
             # Import variables into scope
             trixi_include_changeprecision(Float32, @__MODULE__,