CPLEX.jl is an interface to the IBM® ILOG® CPLEX® Optimization Studio. It provides an interface to the low-level C API, as well as an implementation of the solver-independent MathProgBase and MathOptInterface API's.

You cannot use CPLEX.jl without having purchased and installed a copy of CPLEX Optimization Studio from IBM. However, CPLEX is available for free to academics and students.

This package is available free of charge and in no way replaces or alters any functionality of IBM's CPLEX Optimization Studio product.

Note: This wrapper is maintained by the JuliaOpt community and is not officially supported by IBM. However, we thank IBM for providing us with a CPLEX license to test CPLEX.jl on Travis. If you are a commercial customer interested in official support for CPLEX in Julia, let them know!.

1. First, you must obtain a copy of the CPLEX software and a license; trial versions and academic licenses are available here.

2. Once CPLEX is installed on your machine, point the LD_LIBRARY_PATH variable to the directory containing the CPLEX library by adding, for example, export LD_LIBRARY_PATH="/path/to/cplex/bin/x86-64_linux":$LD_LIBRARY_PATH to your start-up file (e.g. .bash_profile, [adding library path on Ubuntu](http://stackoverflow.com/questions/13428910/how-to-set-the-environmental-variable-ld-library-path-in-linux for a)). On linux, make sure this directory contains libcplexXXX.so where XXX is stands for the version number; on OS-X the file should be named libcplexXXX.dylib. Alternatively, you can also use the CPLEX_STUDIO_BINARIES environment variable as follows:

$ CPLEX_STUDIO_BINARIES=/path/to/cplex/bin/x86-64_linux julia -e 'import Pkg; Pkg.add("CPLEX"); Pkg.build("CPLEX")'

3. At the Julia prompt, run

julia> Pkg.add("CPLEX")

(or manually clone this module to your .julia directory).

4. Check that your version is included in deps/build.jl in the aliases for the library dependency; if not, open an issue.

Currently, CPLEX.jl is compatible only with 64-bit CPLEX and 64-bit Julia on Windows. CPLEX.jl attempts to automatically find the CPLEX library based on the CPLEX_STUDIO_BINARIESXXX environmental variable set by the CPLEX installer where XXX is the CPLEX version. For example:

julia> ENV["CPLEX_STUDIO_BINARIES128"] = "C:/IBM/CPLEX_Studio128/cplex/bin/x64_win64"

julia> Pkg.build("CPLEX")

Which version of CPLEX are you trying to install? Currently, CPLEX.jl only supports 1280 and 1290 given recent changes the API. If your CPLEX version is < 1280, you can add the last supported version of CPLEX.jl via julia> ] add [email protected]. However, we recommend that you upgrade your version of CPLEX. If you want to support newer versions of CPLEX not listed above, file an issue with the version number you'd like to support. Some steps need to be taken (like checking for new or renamed parameters) before CPLEX.jl can support new versions.

The most common problem is not setting LD_LIBRARY_PATH correctly. Open a terminal and check the output of

echo $LD_LIBRARY_PATH

is the path to the CPLEX installation. If it's not, did you follow step 2 above?

Hint: on OS X the path should probably be something like /Users/[username]/Applications/IBM/ILOG/CPLEX_Studio[version number]/cplex/bin/x86-64_osx/

The most common problem is not setting CPLEX_STUDIO_BINARIES correctly. Open a Julia prompt and check that the output of

julia> ENV["CPLEX_STUDIO_BINARIES"]

is the path to the CPLEX installation. If you get a key "CPLEX_STUDIO_BINARIES" not found error, make sure the environment variable is set correctly, or just set it from within the Julia prompt

julia> ENV["CPLEX_STUDIO_BINARIES"] = "path/to/cplex/installation"
julia> Pkg.build("CPLEX")

Another alternative is to run

CPLEX_STUDIO_BINARIES="path/to/cplex/installation" julia -e 'Pkg.build("CPLEX")'

The environment variable needs to be CPLEX_STUDIO_BINARIESXXX where XXX is the version of CPLEX.

Solver parameters can be passed through the CplexSolver() object, e.g., CplexSolver(CPX_PARAM_EPINT=1e-8). Parameters match those of the CPLEX documentation. Additionally, the mipstart_effortlevel parameter can be used to tell CPLEX how much effort to put into turning warmstarts into feasible solutions, with possible values CPLEX.CPX_MIPSTART_AUTO, CPLEX.CPX_MIPSTART_CHECKFEAS, CPLEX.CPX_MIPSTART_SOLVEFIXED, CPLEX.CPX_MIPSTART_SOLVEMIP, CPLEX.CPX_MIPSTART_REPAIR, and CPLEX.CPX_MIPSTART_NOCHECK.