Groups   181 of 99+      julia-users › Starting Julia with Julia -p 2 provides 1 worker 11 posts by 3 authors      Iacopo Poli    Apr 19   Hi,  I'm trying to start Julia with more than one worker, but if I type in the terminal for example  julia -p 2 , then in the REPL nworkers   returns 1. I have version 0.5.0-dev+3488 and a Intel Core i5  Macbook Pro Mid 2012 .    Running system_profiler:   system_profiler SPHardwareDataType Hardware:   Hardware Overview:          Model Name: MacBook Pro        Model Identifier: MacBookPro9,2        ...        Total Number of Cores: 2        ...     So I should be able to start Julia with two workers... Any guess why this isn't working?   This message has been deleted.    Greg Plowman    Apr 19     julia -p 2 will start Julia with 2 processes. nprocs   will return 2 nworkers   will return 1  1 less than nprocs     http:  docs.julialang.org en release-0.4 stdlib parallel ?highlight nworkers Base.nworkers       Andre Bieler    Apr 19   As Greg said, the total number of workers is one less than the number of available processes. There is always one master process  with id   1, and not considered a worker  and the remaining workers.  So for julia -p 3 you will get one master process and two workers.  The documentation may be misleading in this context, as it says: Starting with julia -p n provides n worker processes on the local machine.   But nworkers   is actually n-1. However, if you do a  everywhere, the expression will be executed on all n processes.     Iacopo Poli    Apr 19   All of this seems very reasonable... Except for the fact that also nprocs   is returning 1 after calling julia -p 2 :D  I call julia from terminal using export PATH in bash_profile, but the behavior is the same if I go in the directory and call . Julia -p 2  Plus, I think I saw n workers after a call at julia -p n in Julia 0.4 on another machine, but not sure about it...   btw the doc really is misleading, maybe should be restated in more clearly, but it's a minor issue       Andre Bieler    Apr 19   Huh.. I just tried julia -p 2 on version 0.4.5 and it actually starts with 3 processes and 2 workers. So the docs are correct.  Sorry i cant help with the 0.5 version..      Iacopo Poli    Apr 20   I downloaded version 0.4.5, again calling it with -p 2 returns 1 process and 1 worker... I really can't understand why      Greg Plowman    Apr 20   Sorry, I can't really help you with command line julia -p 2 But what happens when you call addprocs   from REPL? Also, what is the value of CPU_CORES  typed at REPL ?    This message has been deleted.    Iacopo Poli    Apr 21   Calling addprocs   from REPL with for example CPU_CORES as argument returns 5 procs and 4 workers as expected, CPU_CORES returns 4  physical cores are 2, but logical ones are 4 . Also rmprocs n  works fine, it lets me remove all procs but the first as I would expect.      Iacopo Poli    Apr 28   A friend on mine encounters the same problem with another Macbook Pro model and El Captain OS.  julia -p N  doesn't work from terminal but addprocs   works as a charm