From f772bd3c87688b73027327ab1eca97db27f41446 Mon Sep 17 00:00:00 2001
From: ChrisRackauckas <me@chrisrackauckas.com>
Date: Fri, 24 Oct 2025 09:42:13 -0400
Subject: [PATCH 1/9] Add OpenCL.jl backend support for CPU-based debugging
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This adds support for OpenCL.jl with pocl as a CPU-based backend for
debugging GPU issues without requiring actual GPU hardware. This is
particularly useful for debugging issues like #375 where complex nested
types fail with GPU kernels.

Changes:
- Add OpenCL to weakdeps and extensions in Project.toml
- Create OpenCLExt extension with CLBackend support
- Add OpenCL backend to test/utils.jl
- Add OpenCL test group to GitHub Actions CI
- Update README to document OpenCL backend

The OpenCL backend uses pocl_jll as a CPU target that behaves like GPU
targets, allowing developers to reproduce and debug GPU-specific issues
in CI or on systems without GPU hardware.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>
---
 .github/workflows/CI.yml |  1 +
 Project.toml             |  4 ++++
 README.md                |  1 +
 ext/OpenCLExt.jl         | 11 +++++++++++
 test/utils.jl            |  3 +++
 5 files changed, 20 insertions(+)
 create mode 100644 ext/OpenCLExt.jl

diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 99e14c44..9b5a46d6 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -34,6 +34,7 @@ jobs:
         group:
           - CPU
           - JLArrays
+          - OpenCL
     uses: "SciML/.github/.github/workflows/tests.yml@master"
     with:
       julia-version: "${{ matrix.version }}"
diff --git a/Project.toml b/Project.toml
index b5733067..cbe8d943 100644
--- a/Project.toml
+++ b/Project.toml
@@ -30,6 +30,7 @@ AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
+OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 
 [extensions]
@@ -37,6 +38,7 @@ AMDGPUExt = ["AMDGPU"]
 CUDAExt = ["CUDA"]
 JLArraysExt = ["JLArrays"]
 MetalExt = ["Metal"]
+OpenCLExt = ["OpenCL"]
 oneAPIExt = ["oneAPI"]
 
 [compat]
@@ -53,6 +55,7 @@ KernelAbstractions = "0.9"
 LinearSolve = "3"
 Metal = "1"
 MuladdMacro = "0.2"
+OpenCL = "0.9"
 Parameters = "0.12"
 RecursiveArrayTools = "3"
 SciMLBase = "2.92"
@@ -70,5 +73,6 @@ CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
 GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
+OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
diff --git a/README.md b/README.md
index cdf4e30a..e6a4ac90 100644
--- a/README.md
+++ b/README.md
@@ -36,6 +36,7 @@ SciML's GPU support extends to a wide array of hardware, including:
 | AMD              | ROCm                | [AMDGPU.jl](https://github.com/JuliaGPU/AMDGPU.jl) | `AMDGPU.ROCBackend()`    |
 | Intel            | OneAPI              | [OneAPI.jl](https://github.com/JuliaGPU/oneAPI.jl) | `oneAPI.oneAPIBackend()` |
 | Apple (M-Series) | Metal               | [Metal.jl](https://github.com/JuliaGPU/Metal.jl)   | `Metal.MetalBackend()`   |
+| CPU (for debugging) | OpenCL           | [OpenCL.jl](https://github.com/JuliaGPU/OpenCL.jl) | `OpenCL.CLBackend()`     |
 
 For this tutorial we will demonstrate the CUDA backend for NVIDIA GPUs, though any of the other GPUs can be
 used by simply swapping out the `backend` choice.
diff --git a/ext/OpenCLExt.jl b/ext/OpenCLExt.jl
new file mode 100644
index 00000000..fbfdf4c9
--- /dev/null
+++ b/ext/OpenCLExt.jl
@@ -0,0 +1,11 @@
+module OpenCLExt
+using OpenCL
+import DiffEqGPU
+
+using .OpenCL
+import .OpenCL: CLBackend
+
+DiffEqGPU.maxthreads(::CLBackend) = 256
+DiffEqGPU.maybe_prefer_blocks(::CLBackend) = CLBackend()
+
+end
diff --git a/test/utils.jl b/test/utils.jl
index a60bb9e0..58e4786f 100644
--- a/test/utils.jl
+++ b/test/utils.jl
@@ -11,6 +11,9 @@ elseif GROUP == "oneAPI"
 elseif GROUP == "Metal"
     using Metal
     Metal.MetalBackend()
+elseif GROUP == "OpenCL"
+    using OpenCL
+    OpenCL.CLBackend()
 elseif GROUP == "JLArrays"
     using JLArrays
     JLArrays.JLBackend()

From d93757022b785938846edcea48a5f6bbf411af2e Mon Sep 17 00:00:00 2001
From: ChrisRackauckas <me@chrisrackauckas.com>
Date: Fri, 24 Oct 2025 09:50:14 -0400
Subject: [PATCH 2/9] Remove OpenCL and pocl_jll from direct dependencies

They should only be in weakdeps and extras, not in the main deps section.
---
 Project.toml | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/Project.toml b/Project.toml
index cbe8d943..f0fd5754 100644
--- a/Project.toml
+++ b/Project.toml
@@ -30,7 +30,6 @@ AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
-OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 
 [extensions]
@@ -74,5 +73,5 @@ GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
 OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
-oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"

From 709b4298e78fda3562f11322485077607ac6529b Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Fri, 24 Oct 2025 09:54:01 -0400
Subject: [PATCH 3/9] Update README.md

---
 README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/README.md b/README.md
index e6a4ac90..8df6285b 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@ SciML's GPU support extends to a wide array of hardware, including:
 | AMD              | ROCm                | [AMDGPU.jl](https://github.com/JuliaGPU/AMDGPU.jl) | `AMDGPU.ROCBackend()`    |
 | Intel            | OneAPI              | [OneAPI.jl](https://github.com/JuliaGPU/oneAPI.jl) | `oneAPI.oneAPIBackend()` |
 | Apple (M-Series) | Metal               | [Metal.jl](https://github.com/JuliaGPU/Metal.jl)   | `Metal.MetalBackend()`   |
-| CPU (for debugging) | OpenCL           | [OpenCL.jl](https://github.com/JuliaGPU/OpenCL.jl) | `OpenCL.CLBackend()`     |
+| CPU (fast kernels) | OpenCL           | [OpenCL.jl](https://github.com/JuliaGPU/OpenCL.jl) | `OpenCL.CLBackend()`     |
 
 For this tutorial we will demonstrate the CUDA backend for NVIDIA GPUs, though any of the other GPUs can be
 used by simply swapping out the `backend` choice.

From f9bedc2b77c139108a043b770b11b5a6b849c2a7 Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Fri, 24 Oct 2025 10:00:48 -0400
Subject: [PATCH 4/9] Update Project.toml

---
 Project.toml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/Project.toml b/Project.toml
index f0fd5754..ef88c09c 100644
--- a/Project.toml
+++ b/Project.toml
@@ -30,6 +30,7 @@ AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
+OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 
 [extensions]

From 9a1ec018764d65063a56aa462131e5683f025343 Mon Sep 17 00:00:00 2001
From: Christopher Rackauckas <accounts@chrisrackauckas.com>
Date: Fri, 24 Oct 2025 10:22:36 -0400
Subject: [PATCH 5/9] Update Project.toml

---
 test/Project.toml | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test/Project.toml b/test/Project.toml
index 6e853ca2..afbed817 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -8,6 +8,7 @@ ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 GPUArraysCore = "46192b85-c4d5-4398-a991-12ede77f4527"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
+OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 Optimization = "7f7a1694-90dd-40f0-9382-eb1efda571ba"
 OptimizationOptimisers = "42dfb2eb-d2b4-4451-abcd-913932933ac1"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"

From 3fb876c34830fce9fc21cc6a39a7bae0be39913f Mon Sep 17 00:00:00 2001
From: ChrisRackauckas <me@chrisrackauckas.com>
Date: Sat, 25 Oct 2025 09:30:59 -0400
Subject: [PATCH 6/9] Fix backend type name: CLBackend -> OpenCLBackend

The correct backend type name in OpenCL.jl is OpenCLBackend, not CLBackend.
---
 ext/OpenCLExt.jl | 6 +++---
 test/utils.jl    | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/ext/OpenCLExt.jl b/ext/OpenCLExt.jl
index fbfdf4c9..c2a038bf 100644
--- a/ext/OpenCLExt.jl
+++ b/ext/OpenCLExt.jl
@@ -3,9 +3,9 @@ using OpenCL
 import DiffEqGPU
 
 using .OpenCL
-import .OpenCL: CLBackend
+import .OpenCL: OpenCLBackend
 
-DiffEqGPU.maxthreads(::CLBackend) = 256
-DiffEqGPU.maybe_prefer_blocks(::CLBackend) = CLBackend()
+DiffEqGPU.maxthreads(::OpenCLBackend) = 256
+DiffEqGPU.maybe_prefer_blocks(::OpenCLBackend) = OpenCLBackend()
 
 end
diff --git a/test/utils.jl b/test/utils.jl
index 58e4786f..730cd880 100644
--- a/test/utils.jl
+++ b/test/utils.jl
@@ -13,7 +13,7 @@ elseif GROUP == "Metal"
     Metal.MetalBackend()
 elseif GROUP == "OpenCL"
     using OpenCL
-    OpenCL.CLBackend()
+    OpenCL.OpenCLBackend()
 elseif GROUP == "JLArrays"
     using JLArrays
     JLArrays.JLBackend()

From 08ecdc925ed194db0e50b88892aa9b4445c1124a Mon Sep 17 00:00:00 2001
From: ChrisRackauckas <me@chrisrackauckas.com>
Date: Sat, 25 Oct 2025 09:39:31 -0400
Subject: [PATCH 7/9] Update to OpenCL v0.10 with KernelAbstractions backend
 support

- Update compat to allow OpenCL v0.9 and v0.10
- Add OpenCL back to weakdeps (it was accidentally removed)
- Tested with OpenCL v0.10.6 which includes OpenCLBackend type
- OpenCLExt now compiles and works correctly with OpenCL v0.10
---
 Project.toml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Project.toml b/Project.toml
index ef88c09c..d4d1eb4d 100644
--- a/Project.toml
+++ b/Project.toml
@@ -15,6 +15,7 @@ KernelAbstractions = "63c18a36-062a-441e-b654-da1e3ab1ce7c"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 LinearSolve = "7ed4a6bd-45f5-4d41-b270-4a48e9bafcae"
 MuladdMacro = "46d2c3a1-f734-5fdb-9937-b9b9aeba4221"
+OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 Parameters = "d96e819e-fc66-5662-9728-84c9c7592b0a"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 RecursiveArrayTools = "731186ca-8d62-57ce-b412-fbd966d074cd"
@@ -30,7 +31,6 @@ AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
-OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 
 [extensions]
@@ -55,7 +55,7 @@ KernelAbstractions = "0.9"
 LinearSolve = "3"
 Metal = "1"
 MuladdMacro = "0.2"
-OpenCL = "0.9"
+OpenCL = "0.9, 0.10"
 Parameters = "0.12"
 RecursiveArrayTools = "3"
 SciMLBase = "2.92"

From 2db573657737a2aceaffd300cc24809d16691e44 Mon Sep 17 00:00:00 2001
From: ChrisRackauckas <me@chrisrackauckas.com>
Date: Sat, 25 Oct 2025 10:01:45 -0400
Subject: [PATCH 8/9] Add pocl_jll for CPU-based OpenCL testing

- Add pocl_jll to extras for testing
- Update test/utils.jl to load pocl_jll when GROUP=OpenCL
- OpenCL backend requires pocl_jll to provide CPU-based OpenCL drivers
- Without pocl_jll, OpenCL has no platforms/devices available
---
 Project.toml  | 3 ++-
 test/utils.jl | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/Project.toml b/Project.toml
index d4d1eb4d..8efec9ea 100644
--- a/Project.toml
+++ b/Project.toml
@@ -15,7 +15,6 @@ KernelAbstractions = "63c18a36-062a-441e-b654-da1e3ab1ce7c"
 LinearAlgebra = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"
 LinearSolve = "7ed4a6bd-45f5-4d41-b270-4a48e9bafcae"
 MuladdMacro = "46d2c3a1-f734-5fdb-9937-b9b9aeba4221"
-OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 Parameters = "d96e819e-fc66-5662-9728-84c9c7592b0a"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 RecursiveArrayTools = "731186ca-8d62-57ce-b412-fbd966d074cd"
@@ -31,6 +30,7 @@ AMDGPU = "21141c5a-9bdb-4563-92ae-f87d6854732e"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
 JLArrays = "27aeb0d3-9eb9-45fb-866b-73c2ecf80fcb"
 Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
+OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
 
 [extensions]
@@ -76,3 +76,4 @@ Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
 OpenCL = "08131aa3-fb12-5dee-8b74-c09406e224a2"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 oneAPI = "8f75cd03-7ff8-4ecb-9b8f-daf728133b1b"
+pocl_jll = "627d6b7a-bbe6-5189-83e7-98cc0a5aeadd"
diff --git a/test/utils.jl b/test/utils.jl
index 730cd880..b89b9d16 100644
--- a/test/utils.jl
+++ b/test/utils.jl
@@ -12,7 +12,7 @@ elseif GROUP == "Metal"
     using Metal
     Metal.MetalBackend()
 elseif GROUP == "OpenCL"
-    using OpenCL
+    using OpenCL, pocl_jll
     OpenCL.OpenCLBackend()
 elseif GROUP == "JLArrays"
     using JLArrays

From 9629e9c3c982b2caefb1ccc82290a3cbd5819f43 Mon Sep 17 00:00:00 2001
From: ChrisRackauckas <me@chrisrackauckas.com>
Date: Sat, 25 Oct 2025 11:29:27 -0400
Subject: [PATCH 9/9] Add pocl_jll to test/Project.toml

CI tests need pocl_jll in the test environment dependencies.
---
 test/Project.toml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/test/Project.toml b/test/Project.toml
index afbed817..6c2c0ed1 100644
--- a/test/Project.toml
+++ b/test/Project.toml
@@ -14,10 +14,11 @@ OptimizationOptimisers = "42dfb2eb-d2b4-4451-abcd-913932933ac1"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
 SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
+SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 StochasticDiffEq = "789caeaf-c7a9-5a7d-9973-96adeb23e2a0"
-SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
+pocl_jll = "627d6b7a-bbe6-5189-83e7-98cc0a5aeadd"