From 4b05e3909a7922d11d0697075932dabc7b98ee54 Mon Sep 17 00:00:00 2001
From: Charles Kawczynski <kawczynski.charles@gmail.com>
Date: Tue, 15 Oct 2024 14:50:59 -0400
Subject: [PATCH] Reduce number of specialized methods in stencil kernels

---
 src/Operators/finitedifference.jl | 44 +++++++++++--------------------
 1 file changed, 16 insertions(+), 28 deletions(-)

diff --git a/src/Operators/finitedifference.jl b/src/Operators/finitedifference.jl
index 12740e2b28..51744cfce2 100644
--- a/src/Operators/finitedifference.jl
+++ b/src/Operators/finitedifference.jl
@@ -3327,30 +3327,6 @@ function Base.similar(
     return Field(Eltype, sp)
 end
 
-function _serial_copyto!(field_out::Field, bc, Ni::Int, Nj::Int, Nh::Int)
-    space = axes(field_out)
-    bounds = window_bounds(space, bc)
-    bcs = bc # strip_space(bc, space)
-    @inbounds for h in 1:Nh, j in 1:Nj, i in 1:Ni
-        apply_stencil!(space, field_out, bcs, (i, j, h), bounds)
-    end
-    return field_out
-end
-
-function _threaded_copyto!(field_out::Field, bc, Ni::Int, Nj::Int, Nh::Int)
-    space = axes(field_out)
-    bounds = window_bounds(space, bc)
-    bcs = bc # strip_space(bc, space)
-    @inbounds begin
-        Threads.@threads for h in 1:Nh
-            for j in 1:Nj, i in 1:Ni
-                apply_stencil!(space, field_out, bcs, (i, j, h), bounds)
-            end
-        end
-    end
-    return field_out
-end
-
 function strip_space(bc::StencilBroadcasted{Style}, parent_space) where {Style}
     current_space = axes(bc)
     new_space = placeholder_space(current_space, parent_space)
@@ -3368,15 +3344,27 @@ function Base.copyto!(
         Broadcasted{ColumnStencilStyle},
     },
 )
-    space = axes(bc)
+    space = axes(field_out)
     local_geometry = Spaces.local_geometry_data(space)
     (Ni, Nj, _, _, Nh) = size(local_geometry)
-    context = ClimaComms.context(axes(field_out))
+    context = ClimaComms.context(space)
     device = ClimaComms.device(context)
+    bounds = window_bounds(space, bc)
+    bcs = strip_space(bc, space)
     if (device isa ClimaComms.CPUMultiThreaded) && Nh > 1
-        return _threaded_copyto!(field_out, bc, Ni, Nj, Nh)
+        @inbounds begin
+            Threads.@threads for h in 1:Nh
+                for j in 1:Nj, i in 1:Ni
+                    apply_stencil!(space, field_out, bcs, (i, j, h), bounds)
+                end
+            end
+        end
+    else
+        @inbounds for h in 1:Nh, j in 1:Nj, i in 1:Ni
+            apply_stencil!(space, field_out, bcs, (i, j, h), bounds)
+        end
     end
-    return _serial_copyto!(field_out, bc, Ni, Nj, Nh)
+    return field_out
 end
 
 function window_bounds(space, bc)