UndefVarError: backend not defined in GPUArrays

[CarloLucibello]

We are seeing in Flux's cuda CI runs a UndefVarError: backend not defined in GPUArrays error
https://buildkite.com/julialang/flux-dot-jl/builds/5197#0193677c-c51b-46fe-b985-d393adee576f/375-655
Possibly it is a GPUArrays v10.3 problem, but posting here since I think current CUDA.jl release is blocking the upgrade to GPUArrays v11. Can we tag a new CUDA.jl release?

[maleadt]

Can we tag a new CUDA.jl release?

Not right now, no. It will take a couple of weeks, or longer, to iron out the performance issues resulting from the move to KA.jl.

UndefVarError: backend not defined in GPUArrays

The backend function was removed from GPUArrays v11 / GPUArraysCore v0.2. How did you end up with these versions installed? The latest CUDA.jl does explicitly not support this version:

CUDA.jl/Project.toml

Line 63 in a1db081

GPUArrays = "10.0.1"

[CarloLucibello]

This is actually a problem with the way in which tests in Flux work, adding CUDA after the environment is loaded
https://github.com/FluxML/Flux.jl/blob/cb76e9d9c56f9ba7695b62a7505db010dbcf4961/test/runtests.jl#L73
which ends up installing incompatible versions of packages.
I will patch this by adding the compact bound GPUArraysCore=0.1.