Setting Number of Threads at startup for VS Code

New to Julia
1

Hello,

I am trying to set the number of threads (such as 4) in Julia by using the command:
JULIA_NUM_THREADS=4
in CMD in window before launching Julia, which works.

However, I need to set this issue inside “.jl” file by typing the command:
$ JULIA_NUM_THREADS=4 ./julia
at the beginning but it seems not working when I check the threads number by “Threads.threadid()” in the opened REPL.
By the way, I am using VS code to run the “.jl” file.

Thanks!
Amro

2
3

Thanks for the reply! I tried and it works.

However, can we define the number of threads from inside the “.jl” file rather set it manually?

4

no, because it’s defined when the Julia process starts, which is before anything inside a .jl file is read. Same reason you can’t change number of threads on the fly

5

Thanks, I got it except the term “on the fly”.

Can we create a file (not .jl) which sets the number of threads and also calls my .jl file?

6

you open up a Julia REPL, Threads.nthreads() shows a number, there’s no way to change this value within the same session (“on the fly”, as this Julia process is running).

yeah just use a bash or powershell steering script, or even a julia script :slight_smile:

7

yeah just use a bash or powershell steering script, or even a julia script :slight_smile:
[/quote]
Can you please give me an example using the julia script?

8

well this is super backwards because you could have just called Julia on your original script… but here we go:

akako@ThinkX /tmp> cat t.jl
run(`julia -t $(ARGS[1]) myscript.jl`)
akako@ThinkX /tmp> cat myscript.jl 
println(Threads.nthreads())
akako@ThinkX /tmp> julia t.jl 1
1
akako@ThinkX /tmp> julia t.jl 3
3

by any chance you are just looking for the -t? Multi-Threading · The Julia Language

9

I am not sure if I made it right.
1- I opened VS code
2- I created a new .jl file and I put in it
akako@ThinkX /tmp> cat t.jl

run(julia -t $(ARGS[5]) Test1.jl)

akako@ThinkX /tmp> cat Test1.jl

println(Threads.nthreads())
akako@ThinkX /tmp> julia t.jl 5

(Test1 is my .jl file and the number of the threads is 5).
3- Then click “Julia: Excute file in REPL”

10

what’s your end goal

11

Create a file that (1- defines the number of threads; 2- and executes some calculations in julia script).
I need to open this file by VScode and run it

12

what’s wrong with using VSCode’s terminal to run julia -t <num> yourscriipt.jl?

13

I just want to make it more automatic, rather than typing the above line.
However, while I typing the above line I got the following error"

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