Conditional @threads macro causing @threads requires a for loop expression error

[FrancoisFEM]

Hello,

I frequently use @threads in my code, especially in personal packages. However, I often face tricky-to-debug errors when code is run "behind" a @threads macro. Because of that, I wanted to create a sort of overload or conditional version of @threads, something like @conditionalThreads(cond::Bool, loop).

I came up with this solution:
` using Base.Threads

macro Conditionalthreads(cond, loop)
if loop.head != :for error("@Conditionalthreads must be applied to a for loop.")
end quote
if $(esc(cond)) @threads $(esc(loop))
else $(esc(loop))
end end
` end

@Conditionalthreads !isinteractive() for i in 1:5 println("i = ", i)
` end

However, I get this error:

ERROR: LoadError: ArgumentError: @threads requires a forloop expressionStacktrace:
[1] var"@threads"(__source__::LineNumberNode, __module__::Module, args::Vararg{Any}) @ Base.Threads ./threadingconstructs.jl:400
[2] eval @ ./boot.jl:430 [inlined]
[3] include_string(mapexpr::typeof(identity), mod::Module, code::String, filename::String) @ Base ./loading.jl:2643
`in expression starting at /home/francois.roux/OPTILE/readnetcdf/testmaybe_thread.jl:9

While I understand the error (there is some kind of verification inside @threads), I do not know how to fix this problem. :(

If anyone has an idea...

[sgaure]

Note that this type of question is better suited for https://discourse.julialang.org/. There's much more activity than here in github Discussions.

You can do something like this, though there may be more intuitive ways.

macro Conditionalthreads(cond, loop)
    if loop.head != :for
        error("@Conditionalthreads must be applied to a for loop.")
    end
    thr = :(@threads)
    push!(thr.args, loop)
    Expr(:if, cond, thr, loop) |> esc
end

@Conditionalthreads !isinteractive() for i in 1:5 println("i = ", i) end

[FrancoisFEM]

Hi,
Thanks for the answers — that’s exactly what I was trying to achieve 🙂.
I just have one last adjustment: isinteractive() doesn’t seem to be the right control condition. The intention of this macro is to disable @threads when debug mode is activated. In my initial tests, isinteractive() looked like a good solution, but in practice I often run my code from bash, which isn’t interactive.
BR
François
PS : next time I will post on https://discourse.julialang.org/.