Frequently Asked Questions (FAQ)

Why can't I build packages in Julia?

In order to build the packages of Julia, cmake must be installed on Unix systems. In addition, csh must be installed in order to open a MATLAB session. Both packages can be installed using system commands (must have sudo rights):

$ sudo apt-get install cmake csh

Why do the Julia instances on remote workers not start?

There can be several reasons, but majorly, you must ensure that the Julia configuration on all the nodes is the same than on the host node.

Make sure that the lib folder in ~/.julia is the same on the ALL the nodes (.ji files in /.julia/lib/v0.x). The exact (bitwise) same usr/lib/julia/* binaries, which requires copying them to each machine. In order to have the same .ji files on all nodes, it is recommended to copy them from a central storage space (or cloud) to the library folder on the node:

$ cp ~/centralStorage/CPLEX.ji ~/.julia/lib/v0.x/
$ cp ~/centralStorage/MathProgBase.ji ~/.julia/lib/v0.x/

Once all the .ji have been copied, do not use or build the modules on the nodes. In other words, do not type using CPLEX/MathProgBase at the REPL. Alternatively, you may set JULIA_PKGDIR to a cloud or common storage location.

Some workers are dying - how can I avoid this?

Set the enviornment variables explicity on the host in the .bashrc file or /etc/profile.d


I cannot access the SSH nodes. What am I doing wrong?

You must have configured your ssh keys in order to be able to access the nodes, or you must access the nodes without credentials.

My machine is a Windows machine, and everything is so slow. What can I do?

Some Windows users may have to wait a while when installing Julia. The performance of COBRA.jl is unaffected by this relatively long load time. However, you may try these avenues of fixing this:

Try setting the git parameters correctly (using git bash that you can download from here):

$ git config --global core.preloadindex true
$ git config --global core.fscache true
$ git config --global gc.auto 256

Make sure that you set the following environment variables correctly:

$ set JULIA_PKGDIR=C:\Users\<yourUsername>\.julia\vx.y.z
$ set HOME=C:\Users\<yourUsername>\AppData\Local\Julia-x.y.z

Make sure that the .julia folder is not located on a network. This slows the processes in Julia down dramatically.

How can I generate the documentation?

You can generate the documentation using Documenter.jl by typing in /docs:

$ julia --color=yes makeDoc.jl

How can I get the latest version of COBRA.jl

If you want to enjoy the latest untagged (but eventually unstable) features of COBRA.jl, do the following from within Julia:

julia> Pkg.checkout("COBRA", "develop")