Improve AD module

Project.toml

@@ -26,7 +26,7 @@ ParallelStencil_MetalExt = "Metal"
 AMDGPU = "0.6, 0.7, 0.8, 0.9, 1"
 CUDA = "3.12, 4, 5"
 CellArrays = "0.3"
-Enzyme = "0.11, 0.12, 0.13"
+Enzyme = "0.12, 0.13"
 MacroTools = "0.5"
 Metal = "1.2"
 Polyester = "0.7"

src/AD.jl

@@ -7,8 +7,8 @@ Provides GPU-compatible wrappers for automatic differentiation functions of the
     import ParallelStencil.AD
 
 # Functions
-- `autodiff_deferred!`: wraps function `autodiff_deferred`.
-- `autodiff_deferred_thunk!`: wraps function `autodiff_deferred_thunk`.
+- `autodiff_deferred!`: wraps function `autodiff_deferred`, promoting all arguments that are not Enzyme.Annotations to Enzyme.Const.
+- `autodiff_deferred_thunk!`: wraps function `autodiff_deferred_thunk`, promoting all arguments that are not Enzyme.Annotations to Enzyme.Const.
 
 # Examples
     const USE_GPU = true
@@ -43,9 +43,6 @@ Provides GPU-compatible wrappers for automatic differentiation functions of the
 
     main()
 
-!!! note "Enzyme runtime activity default"
-    If ParallelStencil is initialized with Threads, then `Enzyme.API.runtimeActivity!(true)` is called to ensure correct behavior of Enzyme. If you want to disable this behavior, then call `Enzyme.API.runtimeActivity!(false)` after loading ParallelStencil.
-
 To see a description of a function type `?<functionname>`.
 """
 module AD

src/ParallelKernel/EnzymeExt/AD.jl

@@ -7,11 +7,8 @@ Provides GPU-compatible wrappers for automatic differentiation functions of the
     import ParallelKernel.AD
 
 # Functions
-- `autodiff_deferred!`: wraps function `autodiff_deferred`.
-- `autodiff_deferred_thunk!`: wraps function `autodiff_deferred_thunk`.
-
-!!! note "Enzyme runtime activity default"
-    If ParallelKernel is initialized with Threads, then `Enzyme.API.runtimeActivity!(true)` is called to ensure correct behavior of Enzyme. If you want to disable this behavior, then call `Enzyme.API.runtimeActivity!(false)` after loading ParallelStencil.
+- `autodiff_deferred!`: wraps function `autodiff_deferred`, promoting all arguments that are not Enzyme.Annotations to Enzyme.Const.
+- `autodiff_deferred_thunk!`: wraps function `autodiff_deferred_thunk`, promoting all arguments that are not Enzyme.Annotations to Enzyme.Const.
 
 To see a description of a function type `?<functionname>`.
 """

src/ParallelKernel/EnzymeExt/autodiff_gpu.jl

@@ -2,16 +2,17 @@ import ParallelStencil
 import ParallelStencil: PKG_THREADS, PKG_POLYESTER
 import Enzyme
 
+# NOTE: package specific initialization of Enzyme could be done as follows (not needed in the currently supported versions of Enzyme)
 # function ParallelStencil.ParallelKernel.AD.init_AD(package::Symbol)
 #     if iscpu(package)
 #         Enzyme.API.runtimeActivity!(true) # NOTE: this is currently required for Enzyme to work correctly with threads
 #     end
 # end
 
-# ParallelStencil injects a configuration parameter at the end, for Enzyme we need to wrap that parameter as a Annotation
-# for all purposes this ought to be Const. This is not ideal since we might accidentially wrap other parameters the user
-# provided as well. This is needed to support @parallel autodiff_deferred(...)
- function promote_to_const(args::Vararg{Any,N}) where N
+# NOTE: @parallel injects four parameters at the end, which need to be wrapped as Annotations. The current solution is to wrap all
+# arguments which are not already Annotations (all the other arguments must be Annotations). Should this change, then one could 
+# explicitly wrap just the injected parameters.
+function promote_to_const(args::Vararg{Any,N}) where N
     ntuple(Val(N)) do i
         @inline
         if !(args[i] isa Enzyme.Annotation ||

test/ParallelKernel/test_parallel.jl

@@ -133,8 +133,8 @@ eval(:(
                         end
                         return
                     end
-                    @parallel configcall=f!(A, B, a) AD.autodiff_deferred!(Enzyme.Reverse, Const(f!), Const, DuplicatedNoNeed(A, Ā), DuplicatedNoNeed(B, B̄), Const(a))
-                    Enzyme.autodiff_deferred(Enzyme.Reverse, Const(g!),Const, DuplicatedNoNeed(A_ref, Ā_ref), DuplicatedNoNeed(B_ref, B̄_ref), Const(a))
+                    @parallel configcall=f!(A, B, a) AD.autodiff_deferred!(Enzyme.Reverse, f!, Const, DuplicatedNoNeed(A, Ā), DuplicatedNoNeed(B, B̄), Const(a)) # NOTE: f! is automatically promoted to Const.
+                    Enzyme.autodiff_deferred(Enzyme.Reverse, Const(g!), Const, DuplicatedNoNeed(A_ref, Ā_ref), DuplicatedNoNeed(B_ref, B̄_ref), Const(a))
                     @test Array(Ā) ≈ Ā_ref
                     @test Array(B̄) ≈ B̄_ref
                 end