# Setting JULIA\_NUM\_THREADS in an IJulia kernel

**URL:** <https://discourse.julialang.org/t/setting-julia-num-threads-in-an-ijulia-kernel/8301>\
**Category:** General Usage\
**Tags:** jupyter\
**Created:** [January 12, 2018, 4:38am UTC](https://discourse.julialang.org/t/setting-julia-num-threads-in-an-ijulia-kernel/8301 "2018-01-12T04:38:32Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![mohamed82008](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mohamed82008/32/18171_2.png) [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Post date:** [January 12, 2018, 4:38am UTC](https://discourse.julialang.org/t/setting-julia-num-threads-in-an-ijulia-kernel/8301/1 "2018-01-12T04:38:32Z")

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Is there a way to set the JULIA\_NUM\_THREADS environment variable for the IJulia session or kernel?

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**Author:** ![kristoffer.carlsson](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kristoffer.carlsson/32/22_2.png) [@kristoffer.carlsson](https://discourse.julialang.org/u/kristoffer.carlsson)\
**Post date:** [January 12, 2018, 9:29am UTC](https://discourse.julialang.org/t/setting-julia-num-threads-in-an-ijulia-kernel/8301/2 "2018-01-12T09:29:10Z")

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Just set `ENV["JULIA_NUM_THREADS"] = 4` and start the notebook server.

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**Author:** ![oxinabox](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oxinabox/32/206603_2.png) [@oxinabox](https://discourse.julialang.org/u/oxinabox)\
**Post date:** [January 12, 2018, 9:30am UTC](https://discourse.julialang.org/t/setting-julia-num-threads-in-an-ijulia-kernel/8301/3 "2018-01-12T09:30:26Z")

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To my knowledge it is not possible without restarting `jupyter`

What i normally do is

```julia
sh> export JULIA_NUM_THREADS=4
sh> jupyter notebook

```

I guess if you start IJulia from the REPL you can set it in ENV, since it will start a new julia process for the kernal

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<div class="post-metadata">

**Author:** ![mohamed82008](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mohamed82008/32/18171_2.png) [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Post date:** [January 12, 2018, 10:45am UTC](https://discourse.julialang.org/t/setting-julia-num-threads-in-an-ijulia-kernel/8301/4 "2018-01-12T10:45:21Z")

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@kristoffer.carlsson and @oxinabox: both of these work, and make so much sense, thank you! It’s a mystery to me how I didn’t even try any of them before asking I was almost sure I tried them all, but it was only in my head! Thanks a lot.