Most users will have ixmp installed automatically when installing MESSAGEix. The sections below cover other use cases.

Ensure you have first read the prerequisites for understanding and using MESSAGEix. These include specific points of knowledge that are necessary to understand these instructions and choose among different installation options.

To use ixmp from R, see Install R and reticulate in the MESSAGEix documentation.

Use cases for installing ixmp directly include:


Install system dependencies


Python version 3.8 or later is required.

GAMS (required)

ixmp requires GAMS.

  1. Download GAMS for your operating system; either the latest version or, for users not familiar with GAMS licenses, version 29 (see note below).

  2. Run the installer.

  3. Ensure that the PATH environment variable on your system includes the path to the GAMS program:

    • on Windows, in the GAMS installer…

      • Check the box labeled “Use advanced installation mode.”

      • Check the box labeled “Add GAMS directory to PATH environment variable” on the Advanced Options page.

    • on other platforms (macOS or Linux), add the following line to a file such as ~/.bash_profile (macOS), ~/.bashrc, or ~/.profile:

      export PATH=$PATH:/path/to/gams-directory-with-gams-binary


message_ix requires GAMS version 24.8; ixmp has no minimum requirement per se. The latest version is recommended.

GAMS is proprietary software and requires a license to solve optimization problems. To run both the ixmp and message_ix tutorials and test suites, a “free demonstration” license is required; the free license is suitable for these small models. Versions of GAMS up to version 29 include such a license with the installer; since version 30, the free demo license is no longer included, but may be requested via the GAMS website.


If you only have a license for an older version of GAMS, install both the older and the latest versions.

Graphviz (optional)

ixmp.Reporter.visualize uses Graphviz, a program for graph visualization. Installing ixmp causes the graphviz Python package to be installed. If you want to use visualize() or run the test suite, the Graphviz program itself must also be installed; otherwise it is optional.

If you install ixmp using Anaconda, Graphviz is installed automatically via its conda-forge package. For other methods of installation, see the Graphviz download page for downloads and instructions for your system.

Install ixmp

Using Anaconda

After installing GAMS, we recommend that new users install Anaconda, and then use it to install ixmp. Advanced users may choose to install ixmp from source code (next section).

  1. Install Python via either Miniconda or Anaconda. [1] We recommend the latest version; currently Python 3.10. [2]

  2. Open a command prompt. We recommend Windows users use the “Anaconda Prompt” to avoid issues with permissions and environment variables when installing and using ixmp. This program is available in the Windows Start menu after installing Anaconda.

  3. Configure conda to install ixmp from the conda-forge channel [3]:

    $ conda config --prepend channels conda-forge
  4. Create a new conda enviroment. This step is required if using Anaconda, but optional if using Miniconda. This example uses the name ixmp_env, but you can use any name of your choice:

    $ conda create --name ixmp_env
    $ conda activate ixmp_env
  1. Install the ixmp package into the current environment (either base, or another name from step 7, e.g. ixmp_env):

    $ conda install -c conda-forge ixmp


When using Anaconda (not Miniconda), steps (5) through (8) can also be performed using the graphical Anaconda Navigator. See the Anaconda Navigator documentation for how to perform the various steps.

From source

  1. (Optional) If you intend to contribute changes to ixmp, first register a Github account, and fork the ixmp repository. This will create a new repository <user>/ixmp. (Please also see Contributing to development.)

  2. Clone either the main repository, or your fork; using the Github Desktop client, or the command line:

    $ git clone [email protected]:iiasa/ixmp.git
    # or:
    $ git clone [email protected]:USER/ixmp.git
  3. Open a command prompt in the ixmp/ directory that is created, and type:

    $ pip install --editable .[docs,tests,tutorial]

    The --editable flag ensures that changes to the source code are picked up every time import ixmp is used in Python code. The [docs,tests,tutorial] extra dependencies ensure additional dependencies are installed.

  4. (Optional) Run the built-in test suite to check that ixmp functions correctly on your system:

    $ pytest


Run ixmp show-versions on the command line to check that you have all dependencies installed, or when reporting issues.

For Anaconda users experiencing problems during installation of ixmp, check that the following paths are part of the PATH environment variable, and add them if missing:

C:\[YOUR ANACONDA LOCATION]\Anaconda3\Scripts;
C:\[YOUR ANACONDA LOCATION]\Anaconda3\Library\bin;

Install development tools

Developers making changes to the ixmp source may need one or more of the following tools. Users developing models using existing functionality should not need these tools.


Use one of:

Java Development Kit (JDK)
  • Install the Java Development Kit (JDK) for Java SE version 8 from


    At this point, ixmp is not compatible with JAVA SE 9.

  • Follow the JDK website instructions to set the JAVA_HOME environment variable; if JAVA_HOME does not exist, add it as a new system variable.

  • Update your PATH environment variable to point to the JRE binaries and server installation (e.g., C:\Program Files\Java\jdk[YOUR JDK VERSION]\jre\bin\, C:\Program Files\Java\jdk[YOUR JDK VERSION]\jre\bin\server).


    Do not overwrite the existing PATH environment variable, but add to the list of existing paths.