cache construction is no longer type stable

[avik-pal]

I will generate a MWE but the DI extras is not type stable, atleast in the bruss case I tested.

[gdalle]

That is unfortunately expected, as preparation implies dynamically choosing a chunk/batch size B and then putting seeds in batches with type NTuple{B}. It is a bit similar to ForwardDiff's preparation in that sense. I have opened gdalle/DifferentiationInterface.jl#534 to keep track and brainstorm

[avik-pal]

In this case I was testing with a concrete chunksize specified. Without chunksize our code was type-unstable as well.

[gdalle]

On my way to fixing it in gdalle/DifferentiationInterface.jl#535

[gdalle]

Can you confirm that cache construction only used to be type-stable for sparse Jacobians? For dense Jacobians with ForwardDiff I don't see a way to get past ForwardDiff.Chunk(x), which is type-unstable

[avik-pal]

For dense it used to be type stable if AutoForwardDiff had chunksize specified, else it would be type-unstable.

[gdalle]

Okay I need to look at how you achieved type stability in the dense case. Can you point me to where that code lived?
nevermind, I figured it out

[gdalle]

Wait no I still don't have it, how do you statically set a chunk size while ensuring it always remains smaller than the vector length? Do you just let it error if the chunk is too big?

[avik-pal]

I think that case should be an error

[gdalle]

Alright I hadn't understood it that way.

[gdalle]

This issue should be fixed by DI v0.6.5, wanna check?