# Writing a module using paralellization with @everywhere and @parallel

**URL:** https://discourse.julialang.org/t/writing-a-module-using-paralellization-with-everywhere-and-parallel/7334
**Category:** General Usage
**Tags:** parallel, module
**Created:** [November 27, 2017, 1:44pm UTC](https://discourse.julialang.org/t/writing-a-module-using-paralellization-with-everywhere-and-parallel/7334 "2017-11-27T13:44:54Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![tim](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tim/32/6848_2.png) [@tim](https://discourse.julialang.org/u/tim)
#### Post date: [November 27, 2017, 1:44pm UTC](https://discourse.julialang.org/t/writing-a-module-using-paralellization-with-everywhere-and-parallel/7334/1 "2017-11-27T13:44:54Z")

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Hi,  
I am rather new to julia and am trying to speed up some processes by using `@parallel` . But somehow I get confused with the correct way of including a (possible) parallelization in a module.

If I use `@everywhere` inside of a `module` environment, then it’s not found when including the module with `using`, see MWE2 below. (For reference, the code runs fine without the module environment and by simply including the module file.)

Next I understood I simply do not use `@everywhere` inside the module and instead using `@everywhere include("...")` and `@everywhere using ...` in the main script. While that seemingly works, I get a bunch of Warnings when including other modules, see MWE1 below`.

Hence, I probably did not understand the correct way of including parallelization in a module. Could somebody give me a short explanation on how to do that maybe using the examples here?

Best,  
Tim

PS: Yes, I do know there are more effective ways to double the value of an array, the examples below are just meant as illustration (:

**MWE1**  
_MyMain\_parallel.jl_

```julia
@everywhere include("MyModFile_parallel.jl")
println("included MyModFile_parallel.jl")

@everywhere using MyMod: double_it, MyType
println("loaded MyMod")

x_in = MyType[1 3; 5 7]
x_out = SharedArray{MyType}(size(x_in))

println(x_in)
println(x_out)
double_it(x_in, x_out)
println(x_out)

```

_MyMod\_parallel.jl_

```julia
println("inside MyModFile_parallel.jl")

module MyMod
using NearestNeighbors # just loading for testing reasons

MyType = Float64

function double_it_worker(x::MyType)
    2*x
end

function double_it(in_array::Array{MyType}, out_array::SharedArray{MyType})
    # do some random stuff with @parallel
    @assert size(in_array) == size(out_array)
    @sync @parallel for i = 1:length(in_array)
        out_array[i] = double_it_worker(in_array[i])
    end
end

end

```

**MWE2**  
_MyMain\_parallel2.jl_

```julia
include("MyModFile_parallel2.jl")
println("included MyModFile_parallel2.jl")

using MyMod: double_it, MyType
println("loaded MyMod")

x_in = MyType[1 3; 5 7]
x_out = SharedArray{MyType}(size(x_in))

println(x_in)
println(x_out)
double_it(x_in, x_out)
println(x_out)

```

_MyMod\_parallel2.jl_

```julia
println("inside MyModFile_parallel2.jl")

module MyMod
using NearestNeighbors # just loading for testing reasons

@everywhere MyType = Float64

@everywhere function double_it_worker(x::MyType)
    2*x
end

@everywhere function double_it(in_array::Array{MyType}, out_array::SharedArray{MyType})
    # do some random stuff with @parallel
    @assert size(in_array) == size(out_array)
    @sync @parallel for i = 1:length(in_array)
        out_array[i] = double_it_worker(in_array[i])
    end
end

end

```

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<div class="post-metadata">

### Author: ![tictaccat](https://avatars.discourse-cdn.com/v4/letter/t/9f8e36/32.png) [@tictaccat](https://discourse.julialang.org/u/tictaccat)
#### Post date: [October 13, 2021, 5:07pm UTC](https://discourse.julialang.org/t/writing-a-module-using-paralellization-with-everywhere-and-parallel/7334/2 "2021-10-13T17:07:45Z")

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I have the same question.