Error when loading LoopVectorization after ForwardDiff with --compiled-modules=no

[mfsch]

I ran into this error when using OrdinaryDiffEq.jl with julia --compiled-modules=no:

┌ Warning: Error requiring `ForwardDiff` from `LoopVectorization`
│   exception =
│    LoadError: UndefVarError: Dual not defined
│    in expression starting at ~/.julia/packages/LoopVectorization/09Hhf/src/simdfunctionals/vmap_grad.jl:6
└ @ Requires ~/.julia/packages/Requires/7Ncym/src/require.jl:49

The most minimal case I managed to narrow it down to is having a new project with only ForwardDiff and LoopVectorization as dependencies, then starting Julia with --compiled-modules=no and first importing LoopVectorization, then ForwardDiff. When compiled modules are activated or when ForwardDiff is imported first, the error does not appear.

[chriselrod]

Requires bug?

What is your use case for --compiled-modules=no?

[mfsch]

I’ve reported it as JuliaPackaging/Requires.jl#105 – let’s see if the Requires people know why this is happening.

My use case for --compiled-modules=no is that the Julia precompilation mechanism doesn’t interact well with MPI, so if you’re running an MPI program you can get errors if multiple instances of Julia are trying to precompile a package simultaneously. Running without compiled modules avoids this issue and is recommended in the MPI.jl documentation.

[chriselrod]

On master:

# julia -q --startup=no --compiled-modules=no
julia> using LoopVectorization

julia> using ForwardDiff

julia>

Still a Requires bug, but we can work around it here, so it works on master.