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A COIN-OR Project

Projects such as this one are maintained by a small group of volunteers under the auspices of the non-profit COIN-OR Foundation and we need your help! Please consider sponsoring our activities or volunteering to help!

Latest Release

This file is auto-generated from config.yml using the generate_readme script. To make changes, please edit config.yml or the generation scripts here and here.

Osi (Open Solver Interface) provides an abstract base class to a generic linear programming (LP) solver, along with derived classes for specific solvers. Many applications may be able to use the Osi to insulate themselves from a specific LP solver. That is, programs written to the OSI standard may be linked to any solver with an OSI interface and should produce correct results. The OSI has been significantly extended compared to its first incarnation. Currently, the OSI supports linear programming solvers and has rudimentary support for integer programming. Among others the following operations are supported:

  • creating the LP formulation;
  • directly modifying the formulation by adding rows/columns;
  • modifying the formulation by adding cutting planes provided by CGL;
  • solving the formulation (and resolving after modifications);
  • extracting solution information;
  • invoking the underlying solver's branch-and-bound component.

The following is a list of derived Osi classes:

Solver Derived Class Note
Cbc OsiCbc unmaintained
Clp OsiClp
DyLP OsiDylp
GLPK OsiGlpk Glpk
Gurobi OsiGrb
SoPlex OsiSpx SoPlex < 4.0
Vol OsiVol

Each solver interface is in a separate directory of Osi or distributed with the solver itself.

Within COIN-OR, Osi is used by Cgl, Cbc, and Bcp, among others.

The main project managers are Lou Hafer (@LouHafer) and Matt Saltzmann (@mjsaltzman).

An incomplete list of recent changes to Osi are found in the CHANGELOG

Osi is written in C++ and is released as open source under the Eclipse Public License 2.0.

It is distributed under the auspices of the COIN-OR Foundation.

The Osi development site is


Code: DOI


Windows Builds

Linux and MacOS Builds


What follows is a quick start guide for obtaining or building Osi on common platforms. More detailed information is available here.

Docker image

There is a Docker image that provides Osi, as well as other projects in the COIN-OR Optimization Suite here


For newer releases, binaries will be made available as assets attached to releases in Github here. Older binaries are archived as part of Cbc here.

  • Linux (see for a complete listing):

    • arch:
      $ sudo pacman -S  coin-or-osi
    • Debian/Ubuntu:
      $ sudo apt-get install  coinor-osi coinor-libosi-dev
    • Fedora/Redhat/CentOS:
      $ sudo yum install  coin-or-Osi coin-or-Osi-devel
    • freebsd:
      $ sudo pkg install math/osi
    • linuxbrew:
      $ brew install osi
  • Windows: The easiest way to get Osi on Windows is to download an archive as described above.

  • Mac OS X: The easiest way to get Osi on Mac OS X is through Homebrew.

    $ brew tap coin-or-tools/coinor
    $ brew install coin-or-tools/coinor/osi
  • conda (cross-platform, no Windows for now):

    $ conda install coin-or-osi

Due to license incompatibilities, pre-compiled binaries lack some functionality. If binaries are not available for your platform for the latest version and you would like to request them to be built and posted, feel free to let us know on the mailing list.


Source code can be obtained either by

  • Downloading a snapshot of the source code for the latest release version of Osi from the releases page,
  • Cloning this repository from Github, or
  • Using the coinbrew script to get the project and all dependencies (recommended, see below).


Osi has a number of dependencies, which are detailed in config.yml. Dependencies on other COIN-OR projects are automatically downloaded when obtaining the source with coinbrew. For some of the remaining third-party dependencies, automatic download scripts and build wrappers are provided (and will also be automatically run for required and recommended dependencies), while other libraries that are aeasy to obtain must be installed using an appropriate package manager (or may come with your OS by default).

BUILDING from source

These quick start instructions assume you are in a bash shell.

Using coinbrew

To download and build Osi from source, execute the following on the command line.

chmod u+x coinbrew
./coinbrew fetch Osi@master
./coinbrew build Osi

For more detailed instructions on coinbrew, see The coinbrew script will fetch the additional projects specified in the Dependencies section of config.yml.

Without coinbrew (Expert users)

  • Download the source code, e.g., by cloning the git repo
  • Download and install the source code for the dependencies listed in config.yml
  • Build the code as follows (make sure to set PKG_CONFIG_PTH to install directory for dependencies).
./configure -C
make test
make install

Doxygen Documentation

If you have Doxygen available, you can build a HTML documentation by typing

make doxygen-docs

in the build directory. If Osi was built via coinbrew, then the build directory will be ./build/Osi/master by default. The doxygen documentation main file is found at <build-dir>/doxydoc/html/index.html.

If you don't have doxygen installed locally, you can use also find the documentation here.

Project Links

Dynamically loading commercial solver libraries

At build time

It is possible to create an osi build that supports cplex, gurobi and xpress even if you don't have (yet) any of these solvers on your machine using lazylpsolverlibs. To do so, follow these steps:

  1. Install lazylpsolverlibs (follow the instructions of the lazylpsolverlibs wiki)
  2. Use the following command line to configure Osi:
./configure --with-cplex-incdir="$(pkg-config --variable=includedir lazycplex)/lazylpsolverlibs/ilcplex" \
            --with-cplex-lib="$(pkg-config --libs lazycplex)" \ 
            --with-gurobi-incdir="$(pkg-config --variable=includedir lazygurobi)/lazylpsolverlibs" \
            --with-gurobi-lib="$(pkg-config --libs lazygurobi)" \
            --with-xpress-incdir="$(pkg-config --variable=includedir lazyxprs)/lazylpsolverlibs" \
            --with-xpress-lib="$(pkg-config --libs lazyxprs)"
  1. Then follow the normal installation process (make, make install)

At run time

Your build should now support cplex, gurobi and xpress, which means that if you install one of these solvers, osi will be able to use it. At run time, you just need to point one of the environment variables LAZYLPSOLVERLIBS_GUROBI_LIB, LAZYLPSOLVERLIBS_CPLEX_LIB or LAZYLPSOLVERLIBS_XPRS_LIB to the full path of the corresponding solver library. For example:

export LAZYLPSOLVERLIBS_CPLEX_LIB=/usr/ilog/cplex121/bin/x86_debian4.0_4.1/


If pkg-config reports errors during the configure step, try modifying the PKG_CONFIG_PATH variable. Most likely, you need to do:

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig