From 491fac222ce0b30780bdec1bfe75f097b176e5b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alonso=20Mart=C3=ADnez=20Cisneros?= <alonso.mtz99@gmail.com>
Date: Sat, 4 Oct 2025 17:24:40 +0200
Subject: [PATCH 1/2] Initial fixes to support Metal.jl

---
 Project.toml          | 11 +++++----
 ext/TullioCUDAExt.jl  |  4 ++++
 ext/TullioMetalExt.jl | 21 +++++++++++++++++
 src/macro.jl          | 14 +++++++++++
 test/group-2.jl       | 14 ++++++++++-
 test/metal.jl         | 54 +++++++++++++++++++++++++++++++++++++++++++
 6 files changed, 113 insertions(+), 5 deletions(-)
 create mode 100644 ext/TullioMetalExt.jl
 create mode 100644 test/metal.jl

diff --git a/Project.toml b/Project.toml
index e39acb4..993b63f 100644
--- a/Project.toml
+++ b/Project.toml
@@ -11,15 +11,17 @@ Requires = "ae029012-a4dd-5104-9daa-d747884805df"
 
 [weakdeps]
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
+Metal = "dde4c033-4e86-420c-a63e-0dd931031962"
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
 Tracker = "9f7883ad-71c0-57eb-9f7f-b5c9e6d3789c"
-ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 
 [extensions]
 TullioCUDAExt = "CUDA"
+TullioMetalExt = "Metal"
+TullioChainRulesCoreExt = "ChainRulesCore"
 TullioFillArraysExt = "FillArrays"
 TullioTrackerExt = "Tracker"
-TullioChainRulesCoreExt = "ChainRulesCore"
 
 [compat]
 CUDA = "4, 5"
@@ -29,6 +31,7 @@ FillArrays = "0.11, 0.12, 0.13, 1"
 ForwardDiff = "0.10, 1.0"
 KernelAbstractions = "0.9"
 LoopVectorization = "0.12.101"
+Metal = "1.8.1"
 NamedDims = "0.2, 1"
 OffsetArrays = "1"
 Requires = "1"
@@ -39,8 +42,8 @@ Zygote = "0.6.33, 0.7"
 julia = "1.10"  # note that this is the minimum Julia version, 1.11 & 1.12 etc. are allowed & should work.
 
 [extras]
-ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 CUDA = "052768ef-5323-5732-b1bb-66c8b64840ba"
+ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
 FillArrays = "1a297f60-69ca-5386-bcde-b61e274b549b"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 KernelAbstractions = "63c18a36-062a-441e-b654-da1e3ab1ce7c"
@@ -58,4 +61,4 @@ VectorizationBase = "3d5dd08c-fd9d-11e8-17fa-ed2836048c2f"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["Test", "CUDA", "FillArrays", "ForwardDiff", "KernelAbstractions", "LinearAlgebra", "LoopVectorization", "NamedDims", "OffsetArrays", "Pkg", "Printf", "Random", "TensorOperations", "Tracker", "VectorizationBase", "Zygote"]
+test = ["Test", "CUDA", "Metal", "FillArrays", "ForwardDiff", "KernelAbstractions", "LinearAlgebra", "LoopVectorization", "NamedDims", "OffsetArrays", "Pkg", "Printf", "Random", "TensorOperations", "Tracker", "VectorizationBase", "Zygote"]
diff --git a/ext/TullioCUDAExt.jl b/ext/TullioCUDAExt.jl
index 38b4b9b..76e8136 100644
--- a/ext/TullioCUDAExt.jl
+++ b/ext/TullioCUDAExt.jl
@@ -6,6 +6,10 @@ else
     using Tullio, CUDA
 end
 
+if isdefined(@__MODULE__, :Metal) && isdefined(@__MODULE__, :MtlArray)
+    @warn "Loading multiple GPU backends can lead to unexpected bugs"
+end
+
 Tullio.threader(fun!::F, ::Type{T},
     Z::AbstractArray, As::Tuple, Is::Tuple, Js::Tuple,
     redfun, block=0, keep=nothing) where {F<:Function, T<:CUDA.CuArray} =
diff --git a/ext/TullioMetalExt.jl b/ext/TullioMetalExt.jl
new file mode 100644
index 0000000..235f167
--- /dev/null
+++ b/ext/TullioMetalExt.jl
@@ -0,0 +1,21 @@
+module TullioMetalExt
+if !isdefined(Base, :get_extension)
+    using ..Tullio, ..Metal
+else
+    using Tullio, Metal
+end
+
+if isdefined(@__MODULE__, :CUDA) && isdefined(@__MODULE__, :CuArray)
+    @warn "Loading multiple GPU backends can lead to unexpected bugs"
+end
+
+Tullio.threader(fun!::F, ::Type{T},
+    Z::AbstractArray, As::Tuple, Is::Tuple, Js::Tuple,
+    redfun, block=0, keep=nothing) where {F<:Function, T<:Metal.MtlArray} =
+    fun!(T, Z, As..., Is..., Js..., keep)
+
+Tullio.∇threader(fun!::F, ::Type{T},
+    As::Tuple, Is::Tuple, Js::Tuple, block=0) where {F<:Function, T<:Metal.MtlArray} =
+    fun!(T, As..., Is..., Js...,)
+
+end
diff --git a/src/macro.jl b/src/macro.jl
index b8173d7..93446a8 100644
--- a/src/macro.jl
+++ b/src/macro.jl
@@ -1175,6 +1175,20 @@ function make_many_actors(act!, args, ex1, outer::Vector, ex3, inner::Vector, ex
                 end
                 store.verbose==2 && @info "=====KA===== KernelAbstractions CUDA actor $note" verbosetidy(kex2)
                 push!(store.outpre, kex2)
+            elseif isdefined(store.mod, :Metal) && isdefined(store.mod, :MtlArray)
+                info2 = store.verbose>0 ? :(@info "running KernelAbstractions + Metal actor $($note)" maxlog=3 _id=$(hash(store))) : nothing
+                kex2 = quote
+
+                    local @inline function $act!(::Type{<:MtlArray}, $(args...), $KEEP=nothing, $FINAL=true) where {$TYP}
+                        $info2
+                        mtl_kern! = $kernel(MetalBackend())
+                        $(asserts...)
+                        $ACC = mtl_kern!($(args...), $KEEP, $FINAL; ndrange=tuple($(sizes...)), workgroupsize=$workgroupsize)
+                    end
+
+                end
+                store.verbose==2 && @info "=====KA===== KernelAbstractions Metal actor $note" verbosetidy(kex2)
+                push!(store.outpre, kex2)
             end
             info3 = store.verbose>0 ? :(@info "running KernelAbstractions CPU actor $($note)" maxlog=3 _id=$(hash(store))) : nothing
             kex3 = quote
diff --git a/test/group-2.jl b/test/group-2.jl
index 6381206..d09e0f5 100644
--- a/test/group-2.jl
+++ b/test/group-2.jl
@@ -11,7 +11,7 @@ _gradient(x...) = Tracker.gradient(x...)
 @testset "KernelAbstractions + gradients" begin
     A = (rand(3,4));
     B = (rand(4,5));
-    @tullio C[i,k] := A[i,j] * B[j,k]  threads=false  # verbose=2
+    @tullio C[i,k] := A[i,j] * B[j,k]  threads=false # verbose=2
     @test C ≈ A * B
 
     @tullio threads=false # else KernelAbstractions CPU kernels not used
@@ -23,6 +23,16 @@ _gradient(x...) = Tracker.gradient(x...)
     end
 end
 
+try # Load Metal before CUDA to avoid Kernel generation problems
+    using Metal
+    vi = Metal.versioninfo();
+    @info "===== found an Apple GPU, starting Metal tests ====="
+    @testset "===== Metal tests on GPU =====" begin
+        include("metal.jl")
+    end
+catch
+end
+
 using CUDA
 
 if is_buildkite
@@ -37,6 +47,8 @@ if CUDA.has_cuda_gpu()
     end
 end
 
+
+
 @info @sprintf("KernelAbstractions tests took %.1f seconds", time()-t4)
 
 @tullio cuda=false
diff --git a/test/metal.jl b/test/metal.jl
new file mode 100644
index 0000000..7c9df6a
--- /dev/null
+++ b/test/metal.jl
@@ -0,0 +1,54 @@
+using Tullio, Test
+using Metal, KernelAbstractions
+using Tracker, ForwardDiff
+@tullio grad=Base
+
+# matmul
+mul(A, B) = @tullio C[i,k] := A[i,j] * B[j,k]
+
+A = rand(3,40); B = rand(40,500);
+@test A * B ≈ mul(A, B)
+@test mtl(A * B) ≈ mul(mtl(A), mtl(B))
+
+# gradient
+# FIXME: Broken I think
+ΔA = Tracker.gradient((A,B) -> sum(mul(A, B)), A, B)[1]
+@test ΔA ≈ ones(3,500) * B'
+@test mtl(ΔA) ≈ Tracker.gradient((A,B) -> sum(mul(A, B)), mtl(A), mtl(B))[1]
+
+# shifts
+@tullio D[i,j] := A[i,j+k]  k in 0:10
+@test axes(D) == (1:3, 1:30)
+@tullio D_dev[i,j] := mtl(A)[i,j+k]  k in 0:10
+@test D_dev isa MtlArray
+@test D_dev ≈ mtl(D)
+
+# product
+@tullio (*) F[j] := A[i,j]
+@test F ≈ vec(prod(A, dims=1))
+@tullio (*) F_dev[j] := mtl(A)[i,j]
+@test F_dev ≈ mtl(F)
+
+# maximum
+g(A) = @tullio (max) G[j] := A[i,j]
+@test g(A) == vec(maximum(A, dims=1))
+A0 = zero(A);
+A0[findmax(A, dims=1)[2]] .= 1
+@test A0 ≈ Tracker.gradient(sum∘g, A)[1]
+@test g(mtl(A)) isa MtlArray
+@test g(mtl(A)) ≈ mtl(g(A))
+@test mtl(A0) ≈ Tracker.gradient(sum∘g, mtl(A))[1]
+
+# functions
+h(A) = @tullio H[j] := exp(A[i,j]) / log(A[i,j])
+@test h(mtl(A)) isa MtlArray
+@test h(mtl(A)) ≈ mtl(h(A))
+A1 = Tracker.gradient(sum∘h, A)[1]
+@test mtl(A1) ≈ Tracker.gradient(sum∘h, mtl(A))[1]
+
+A, B, C = Metal.rand(2, 2, 2), Metal.rand(2, 2), Metal.rand(2, 2, 2);
+@tullio A[k,i,a] = tanh(B[i,a] + C[k,i,a])
+A2 = similar(A)
+struct Bee{T}; B::T; end
+B2 = Bee(B)
+@test A ≈ @tullio A2[k,i,a] = tanh(B2.B[i,a] + C[k,i,a])

From 8feb9215dc6bc524badf87173dff758e3ed95193 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alonso=20Mart=C3=ADnez=20Cisneros?= <alonso.mtz99@gmail.com>
Date: Sun, 5 Oct 2025 10:42:41 +0200
Subject: [PATCH 2/2] CI updates

---
 .buildkite/pipeline.yml  | 4 ++--
 .github/workflows/ci.yml | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/.buildkite/pipeline.yml b/.buildkite/pipeline.yml
index e8baa59..149ca82 100644
--- a/.buildkite/pipeline.yml
+++ b/.buildkite/pipeline.yml
@@ -3,10 +3,10 @@ env:
   # SECRET_CODECOV_TOKEN: "..."
 
 steps:
-  - label: "Julia 1.8"
+  - label: "Julia 1.11"
     plugins:
       - JuliaCI/julia#v0.5:
-          version: "1.8"
+          version: "1.11"
       - JuliaCI/julia-test#v0.3: ~
       # - JuliaCI/julia-coverage#v0.3:
       #     codecov: true
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c022019..33947b4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -30,12 +30,12 @@ jobs:
           - '1' # automatically expands to the latest stable 1.x release of Julia
           # - 'nightly'
     steps:
-      - uses: actions/checkout@v2
-      - uses: julia-actions/setup-julia@v1
+      - uses: actions/checkout@v5
+      - uses: julia-actions/setup-julia@v2
         with:
           version: ${{ matrix.version }}
           arch: ${{ matrix.arch }}
-      - uses: actions/cache@v1
+      - uses: actions/cache@v4
         env:
           cache-name: cache-artifacts
         with: