BlackBox Optimization: Multiple Cores (Workers) Rather than Threads

General Usage
, ,
5

By default, julia only runs single threaded. You need to set the number of julia threads you want to run by setting the JULIA_NUM_THREADS environment variable before launching julia. For example, on Linux you can do the following:

$ julia
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.4.1 (2020-04-14)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> Base.Threads.nthreads()
1

julia> exit()
$ JULIA_NUM_THREADS=4 julia
               _
   _       _ _(_)_     |  Documentation: https://docs.julialang.org
  (_)     | (_) (_)    |
   _ _   _| |_  __ _   |  Type "?" for help, "]?" for Pkg help.
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 1.4.1 (2020-04-14)
 _/ |\__'_|_|_|\__'_|  |  Official https://julialang.org/ release
|__/                   |

julia> Base.Threads.nthreads()
4

See the multithreading section of the julia manual for more info.

Personally I think it would be nice to be able to change the number of julia threads on the fly, programmatically, but right now that’s not the case.

2 Likes