Julia: call a parallel loop in another file

Question

Suppose I have these two files.

test_file.jl

using Distributed
function loop(N)
  @distributed for i in 1:N
          println(i)
  end
end

test_file_call.jl

include("test_file.jl")
loop(10)

If I run julia -p 2 test_file_call.jl, I expect the function loop executed on different processors, printing out 10 numbers in an arbitrary number. However, this command doesn't render anything.

I'm not sure what I did wrong? It's just a simple loop. Is it possible that I include a parallel loop in file A, write another file, B, that contains this loop, and call B to execute the parallel loop in file A? This two file structure is what I want. Is that doable?

Przemyslaw Szufel · Accepted Answer · 2021-07-24 00:02:59Z

3

The problem is that you forgot to @sync your loop so it exits before it actually has time to print anything.

Hence this should be:

function loop(N)
  @sync @distributed for i in 1:N
      println(i, " ",myid())
  end
end

answered Jul 24, 2021 at 0:02

Przemyslaw Szufel

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2 Comments

user1691278 Over a year ago

What does @sync do?

Przemyslaw Szufel Over a year ago

@sync waits until all lexically-enclosed uses of @async, @spawn, @spawnat and @distributed are complete. Have a look at docs.julialang.org/en/v1/manual/distributed-computing

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