# What topology is used when julia is launched with the -p option

**URL:** <https://discourse.julialang.org/t/what-topology-is-used-when-julia-is-launched-with-the-p-option/4187>\
**Category:** New to Julia\
**Created:** [June 9, 2017, 7:04pm UTC](https://discourse.julialang.org/t/what-topology-is-used-when-julia-is-launched-with-the-p-option/4187 "2017-06-09T19:04:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Jackels](https://avatars.discourse-cdn.com/v4/letter/j/7c8e57/32.png) [@Jackels](https://discourse.julialang.org/u/Jackels)\
**Post date:** [June 9, 2017, 7:04pm UTC](https://discourse.julialang.org/t/what-topology-is-used-when-julia-is-launched-with-the-p-option/4187/1 "2017-06-09T19:04:15Z")

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What topology is used when julia is launched with the -p option.  
E. g. “julia somescript.jl -p 100” Is it all to all or master-slave?  
In case it is not master-slave, is there a way to make it master-slave?

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**Author:** ![anon61610682](https://avatars.discourse-cdn.com/v4/letter/a/ad7895/32.png) [@anon61610682](https://discourse.julialang.org/u/anon61610682)\
**Post date:** [June 20, 2017, 8:05am UTC](https://discourse.julialang.org/t/what-topology-is-used-when-julia-is-launched-with-the-p-option/4187/2 "2017-06-20T08:05:45Z")

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> [@Jackels](#):
>
> What topology is used when julia is launched with the -p option.  
> E. g. “julia somescript.jl -p 100” Is it all to all or master-slave?

It is `:all_to_all`, by default [[ref](https://docs.julialang.org/en/release-0.6/manual/parallel-computing/#Specifying-Network-Topology-(Experimental)-1)].

> [@Jackels](#):
>
> In case it is not master-slave, is there a way to make it master-slave?

Yes, you can make it `:master_slave` [[ref](https://docs.julialang.org/en/release-0.6/manual/parallel-computing/#Specifying-Network-Topology-(Experimental)-1)].

Sure, you need to change slightly the way you run your code. You simply start `julia`, and instide your `somescript.jl`, you `addprocs` with the corresponding topology.