Introduce AutoDI wrapper type for DifferentiationInterface dispatch #140

Copilot · 2026-01-03T11:47:34Z

Original prompt

This section details on the original issue you should resolve

<issue_title>Introduce DI ADType</issue_title>
<issue_description>The ADType can wrap a different ADType and signifies that the DI implementation of the wrapper function for that ADType will be used rather than the native backend ADType

This would solve an important need where packages can't currently distinguish between an intention to directly call a corresponding ad tool vs the di wrapper for said tool. Having this would enable the ability to use, test, and consequently validate/benchmark the two (fixing issues with both usages).

cc @gdalle </issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes Introduce DI ADType #136

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Co-authored-by: wsmoses <[email protected]>

wsmoses · 2026-01-03T14:52:34Z

src/ADTypes.jl

 include("mode.jl")
 include("dense.jl")
 include("sparse.jl")
+include("di.jl")


@copilot move this inside of dense, similarly to AutoReactant

Moved AutoDI into dense.jl (commit 5180120). The separate di.jl file has been removed and all AutoDI definitions are now at the end of dense.jl, similar to how AutoReactant is structured.

wsmoses · 2026-01-03T14:53:18Z

src/ADTypes.jl

 include("mode.jl")
 include("dense.jl")
 include("sparse.jl")
+include("di.jl")


@copilot move this inside of dense, similarly to AutoReactant

This was already addressed in commit 5180120. The AutoDI code has been moved into dense.jl and the separate di.jl file has been removed.

Co-authored-by: wsmoses <[email protected]>

Copilot · 2026-01-03T15:01:31Z

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wsmoses · 2026-01-04T10:07:47Z

@gdalle @ChrisRackauckas any thoughts here?

gdalle · 2026-01-04T14:30:07Z

I'm not sure what the point is. Right now, the semantics of ADTypes objects for many packages out there is "call the backend package through DI". If you introduce AutoDI, then you're creating a world where AutoDI(AutoEnzyme()) and AutoEnzyme() are supposed to mean different things, but effectively mean the same for all the packages who didn't go to the trouble of implementing one extension per AD backend. The only way out of this would be a breaking release of DI which focuses all implementation on AutoDI, which would impact pretty much the entire ecosystem so I am not okay with that.
I recognize the problem that backend objects mean different things to different people. But adding this layer of indirection just increases the number of possible meanings and the resulting confusion. And it also seems like a way to make DI a special case, instead of the general case that it has pretty much become for "normal" users.

gdalle · 2026-01-04T14:46:36Z

Essentially I'd like to take a step back and ask what is best for the everyday users who already have code going through DI for AutoEnzyme and friends:

a new AutoDI wrapper
- with a breaking DI release (this is very tedious to update and people will probably add AutoDI everywhere if all backends are not implemented natively for their use case)
- without a breaking DI release (this might cause confusion and broken promises, as outlined above)
a new AutoNative wrapper which DI wouldn't touch (this seems slightly less disruptive to me)
yet another solution I haven't thought of (perhaps a common type parameters in all backends)

wsmoses · 2026-01-04T14:46:42Z

I mean the point is that AutoDI(AutoEnzyme()) and AutoEnzyme() do mean different things. See the Flux thread which I linked to here which cannot use DI from within Reactant, and thus cannot use DI as a fallback. However, if AutoEnzyme is overloaded to call into Enzyme directly it cannot call the DI implementation of Enzyme. So there needs to be something to distinguish the two.

There doesn't need to be a breaking release. Downstream packages that leverage ADTypes, however, can retain bindings for both DI and AD Tools directly. The downstream packages can (as they do already) choose the semantics.

gdalle · 2026-01-06T11:29:26Z

There doesn't need to be a breaking release. Downstream packages that leverage ADTypes, however, can retain bindings for both DI and AD Tools directly. The downstream packages can (as they do already) choose the semantics.

So in the meantime, I would just add a fallback to DI unwrapping AutoDI, and for all packages who don't bother to have custom implems, AutoDI(AutoEnzyme()) and AutoEnzyme() would keep doing the same thing?

wsmoses · 2026-01-06T22:22:26Z

There doesn't need to be a breaking release. Downstream packages that leverage ADTypes, however, can retain bindings for both DI and AD Tools directly. The downstream packages can (as they do already) choose the semantics.

So in the meantime, I would just add a fallback to DI unwrapping AutoDI, and for all packages who don't bother to have custom implems, AutoDI(AutoEnzyme()) and AutoEnzyme() would keep doing the same thing?

Yeah exactly

gdalle · 2026-01-09T18:09:43Z

I guess I could be okay with that, but I still would like to ask users on the Slack #autodiff channel what they prefer in terms of ergonomics. For instance, maybe an AutoNoDI would be better than an AutoDI. And maybe AutoDI should actually live in DI and not here. Do you want to poll them or should I?

wsmoses · 2026-01-30T22:08:39Z

okay @gdalle from the slack thread it doesn't seem like there's any oppositition to the current design here (which seems to be the only one which adheres to the current adtypes semantics).

Let me know if you have any final thoughts on this PR, and I'll go ahead and approve it

wsmoses · 2026-01-30T22:10:01Z

test/runtests.jl

               ReverseMode,
               SymbolicMode
 using ADTypes: dense_ad,
+               inner_ad,


@copilot fix the merge conflict

Fixed in commit 540c6d5. The merge conflict was due to formatting differences - the main branch switched from JuliaFormatter to Runic.jl formatting. Updated all files to match the new Runic style (4-space indentation, removed explicit returns, adjusted spacing).

…branch Co-authored-by: wsmoses <[email protected]>

gdalle · 2026-01-30T22:16:33Z

src/dense.jl

+"""
+    AutoDI{I<:AbstractADType}
+
+Wraps an AD type to signify that the DifferentiationInterface wrapper should be used instead of calling the backend directly.


I'm not sure about this formulation, because it seems to suggest that anything not wrapped in AutoDI will not use DI. However we agreed that the current behavior of packages who call, say, AutoEnzyme through DI should be preserved. Maybe add a word of caution specifying that "using an ADType directly instead of wrapping it inside AutoDI does not forbid the use of DI"?

gdalle · 2026-01-30T22:17:09Z

src/dense.jl

 end
+
+"""
+    AutoDI{I<:AbstractADType}


Should we call it AutoDifferentiationInterface? I know it is longer but it is more explicit, and coherent with other types in here. People can always define a shortcut if needed

gdalle · 2026-01-30T22:18:23Z

test/di.jl

+            @test mode(di_ad) isa ForwardOrReverseMode
+        elseif mode(ad) isa ReverseMode
+            @test mode(di_ad) isa ReverseMode
+        elseif mode(ad) isa SymbolicMode


This line is never hit

gdalle · 2026-01-30T22:19:05Z

test/di.jl

+    end
+
+    @testset "Nested wrapping" begin
+        # Test that we can wrap AutoDI with AutoSparse and vice versa


I'm not sure we want to support arbitrary wrappings like that. Shouldn't there be a proper way to wrap and an improper one?

Copilot · 2026-01-30T22:20:00Z

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Implement AutoDI wrapper type with tests

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Co-authored-by: wsmoses <[email protected]>

Address code review comments: improve documentation and fix whitespace

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Copilot AI changed the title ~~[WIP] Introduce DI ADType for enhanced wrapping functionality~~ Introduce AutoDI wrapper type for DifferentiationInterface dispatch Jan 3, 2026

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Move AutoDI definition into dense.jl and remove separate di.jl file

5180120

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wsmoses mentioned this pull request Jan 4, 2026

extend gradient to take an ADType argument FluxML/Flux.jl#2645

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Introduce AutoDI wrapper type for DifferentiationInterface dispatch #140

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