JuliaLang / JuliaLang/Distributed.jl
World age problems when using @everywhere in a function
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- Dominant language
- Julia
- Stars
- 55
- Forks
- 19
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Description
I have a julia (1.12) file that is structured something like this:
using Distributed
function main()
@everywhere variable = [0, 1, 2, 3, 4, 5]
for x in variable
println(x^2)
end
end
main()
From my understanding @everywhere should define the variable on every worker, including the main process.
But when I run the code, it give me this error:
UndefVarError: `variable` not defined in `Main` The binding may be too new: running in world age 38716, while current world is 38717.
In a jupyter notebook, I can run main() again a second time, and then it works, since I assume then the world age matches...
Can someone explain what is going on and if there is some way to circumvent this problem? I can fix it by defining it again in the main process variable = [0, 1, 2, 3, 4, 5], or by taking the code out of the main() function but to me that doesn't feel intended.
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the minimal Julia 1.12 reproducer in issue #156, focusing on @everywhere inside main() and the second invocation behavior. Compare execution from a script with the Jupyter notebook case. Done should mean the world-age behavior is explained and a supported way to avoid the failure is identified or documented.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- julia
- Domain
- distributed-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100