From 87ec9407f9282f8dec04d2e1191c1d779c5c98a2 Mon Sep 17 00:00:00 2001
From: CarloLucibello <carlo.lucibello@gmail.com>
Date: Mon, 12 Jan 2026 18:13:51 +0100
Subject: [PATCH] revert 648

---
 ext/NNlibCUDAExt/scatter.jl | 34 ++++++++++++++++++++++------------
 test/ext_cuda/scatter.jl    |  4 ++--
 2 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/ext/NNlibCUDAExt/scatter.jl b/ext/NNlibCUDAExt/scatter.jl
index 9b323d504..cec16e34d 100644
--- a/ext/NNlibCUDAExt/scatter.jl
+++ b/ext/NNlibCUDAExt/scatter.jl
@@ -1,5 +1,15 @@
 # supported op: +, -, *, /, max, min, &, |, mean
-import CUDA.CUSPARSE: AbstractCuSparseArray
+
+## TODO support sparse dst/src/idx
+## See issue https://github.com/FluxML/NNlib.jl/issues/647
+# import CUDA.CUSPARSE: AbstractCuSparseMatrix, CuSparseMatrixCSC, CuSparseMatrixCSR, CuSparseMatrixCOO, AnyCuSparseVector
+# const AnyCuSparseMatrix{Tv,Ti} = Union{
+#     AbstractCuSparseMatrix{Tv,Ti},
+#     CUDA.CuSparseMatrixCSC{Tv,Ti}, # these types do not inherit from AbstractCuSparseMatrix
+#     CUDA.CuSparseMatrixCSR{Tv,Ti}, # but from GPUArrays.AbstractGPUSparseMatrixXXX
+#     CUDA.CuSparseMatrixCOO{Tv,Ti},
+#     }
+# const AnyCuSparseArray{Tv,Ti} = Union{AnyCuSparseVector{Tv,Ti},AnyCuSparseMatrix{Tv,Ti}}
 
 function scatter_kernel!(op::OP, dst, src, idx) where OP
     index = threadIdx().x + (blockIdx().x - 1) * blockDim().x
@@ -45,9 +55,9 @@ function scatter_kernel!(op::OP, dst, src, idx::CUDA.CuDeviceArray{<:CartesianIn
 end
 
 
-function NNlib.scatter!(op::OP, dst::Union{AnyCuArray,AbstractCuSparseArray},
-    src::Union{AnyCuArray,AbstractCuSparseArray},
-    idx::Union{AnyCuArray,AbstractCuSparseArray}) where OP
+function NNlib.scatter!(op::OP, dst::AnyCuArray,
+        src::AnyCuArray,
+        idx::AnyCuArray) where OP
     dims = NNlib.scatter_dims(dst, src, idx)
     args = if dims == 0
         max_idx = length(idx)
@@ -67,9 +77,9 @@ function NNlib.scatter!(op::OP, dst::Union{AnyCuArray,AbstractCuSparseArray},
     return dst
 end
 
-function NNlib.scatter!(op::typeof(mean), dst::Union{AnyCuArray,AbstractCuSparseArray},
-        src::Union{AnyCuArray,AbstractCuSparseArray},
-        idx::Union{AnyCuArray,AbstractCuSparseArray})
+function NNlib.scatter!(op::typeof(mean), dst::AnyCuArray,
+        src::AnyCuArray,
+        idx::AnyCuArray)
     Ns = NNlib.scatter!(+, zero(dst), one.(src), idx)
     dst_ = NNlib.scatter!(+, zero(dst), src, idx)
     dst .+= NNlib.safe_div.(dst_, Ns)
@@ -166,21 +176,21 @@ function ∇scatter_src_kernel!(op::OP, Δsrc, src, idx::CUDA.CuDeviceArray{<:Ca
 end
 
 function NNlib.∇scatter_src(op::Union{typeof(*),typeof(/)}, Δ, dst,
-    src::Union{AnyCuArray{Tsrc,Nsrc},AbstractCuSparseArray},
-    idx::Union{AnyCuArray{Tidx,Nidx},AbstractCuSparseArray}) where {Tsrc,Tidx,Nsrc,Nidx}
-    dims = Nsrc - Nidx
+    src::AnyCuArray,
+    idx::AnyCuArray)
+    dims = ndims(src) - ndims(idx)
     Δsrc = NNlib.modify_src(op, NNlib.gather(Δ, idx), src)
     rev_idx = NNlib.reverse_indices(idx)
     rev_idx = CuArray(map(CUDA.cudaconvert, rev_idx))
 
     if dims == 0
         max_idx = length(idx)
-        args = op, Δsrc, src, idx, rev_idx, max_idx, Tsrc
+        args = op, Δsrc, src, idx, rev_idx, max_idx, eltype(src)
     else
         pre_cart_idx = CartesianIndices(axes(src)[1:dims])
         max_dims_idx = length(pre_cart_idx)
         max_idx = max_dims_idx * length(idx)
-        args = op, Δsrc, src, idx, rev_idx, pre_cart_idx, max_dims_idx, max_idx, Tsrc
+        args = op, Δsrc, src, idx, rev_idx, pre_cart_idx, max_dims_idx, max_idx, eltype(src)
     end
 
     kernel = @cuda launch=false ∇scatter_src_kernel!(args...)
diff --git a/test/ext_cuda/scatter.jl b/test/ext_cuda/scatter.jl
index 10b660e40..a4977f285 100644
--- a/test/ext_cuda/scatter.jl
+++ b/test/ext_cuda/scatter.jl
@@ -21,7 +21,7 @@ idxs = [
         (3,) (5,) (5,) (3,)])),  # CartesianIndex index
 ]
 
-types = [CuArray{Int32}, CuArray{Int64}, CuArray{Float32}, CuArray{Float64}, CuSparseMatrixCSC{Float32}, CuSparseMatrixCSR{Float32}, CuSparseMatrixCOO{Float32}]
+types = [CuArray{Int32}, CuArray{Int64}, CuArray{Float32}, CuArray{Float64}]
 
 
 @testset "scatter" begin
@@ -70,7 +70,7 @@ types = [CuArray{Int32}, CuArray{Int64}, CuArray{Float32}, CuArray{Float64}, CuS
     end
 
 
-    for T = [CuArray{Float32}, CuArray{Float64}, Sparse, CuSparseMatrixCSC{Float32}, CuSparseMatrixCSR{Float32}, CuSparseMatrixCOO{Float32}]
+    for T = [CuArray{Float32}, CuArray{Float64}]
         @testset "$(T)" begin
             @testset "*" begin
                 for idx = idxs, dims = [0, 1]