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.
Install system dependencies
MESSAGEix requires GAMS.
Download GAMS for your operating system; either the latest version or, for users not familiar with GAMS licenses, version 29 (see note below).
Run the installer.
Ensure that the
PATHenvironment 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 macOS, in the GAMS installer…
When prompted to specify the “Installation Type” (step 3 of the installation process), select “Customise”.
Check the box labeled “Add GAMS to PATH”.
If this option is not available see instructions below.
on other platforms (macOS or Linux), add the following line to a file such as
$ export PATH=$PATH:/path/to/gams-directory-with-gams-binary
MESSAGE-MACRO and MACRO require GAMS 24.8.1 or later (see
The latest version is recommended.
GAMS is proprietary software and requires a license to solve optimization problems.
To run both the
ixmp 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.
reporting.Reporter.visualize() uses Graphviz, a program for graph visualization.
Installing message_ix causes the python
graphviz 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 MESSAGEix 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.
After installing GAMS, we recommend that new users install Anaconda, and then use it to install MESSAGEix.
Advanced users may choose to install MESSAGEix using
pip, or from source code (next sections).
If you are not doing this, then skip those sections.
This section is also available as a narrated video on the IIASA YouTube channel. If you are a beginner, you may want to watch the video before attempting the installation yourself.
Install Python via either Miniconda or Anaconda.  We recommend the latest version; currently Python 3.10. 
Open a command prompt. Windows users should use the “Anaconda Prompt” to avoid issues with permissions and environment variables when installing and using MESSAGEix. This program is available in the Windows Start menu after installing Anaconda.
Configure conda to install
message_ixfrom the conda-forge channel :
$ conda config --prepend channels conda-forge
Create a new conda environment and activate it. This step is required if using Anaconda, but optional if using Miniconda. This example uses the name
message_env, but you can use any name of your choice:
$ conda create --name message_env $ conda activate message_env
message-ixpackage into the current environment (either e.g.
message_env, or another name from step 7) :
$ conda install message-ix
Again: at this point, installation is complete.
You do not need to complete the steps in “Using
pip” or “From source”.
Go to the section Check that installation was successful.
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.
pip is Python’s default package management system.
If you install Anaconda (step 4, above), then
pip is also usable.
pip can also be used when Python is installed directly, without using Anaconda.
pipis installed—with Anaconda, or according to the pip documentation.
Open a command prompt and run:
$ pip install message_ix
Install ixmp from source.
(Optional) If you intend to contribute changes to MESSAGEix, first register a Github account, and fork the message_ix repository. This will create a new repository
<user>/message_ix. (Please also see Contributing to development.)
Clone either the main repository, or your fork; using the Github Desktop client, or the command line:
$ git clone [email protected]:iiasa/message_ix.git # or: $ git clone [email protected]:USER/message_ix.git
Open a command prompt in the
message_ixdirectory and type:
$ pip install --editable .[docs,reporting,tests,tutorial]
--editableflag ensures that changes to the source code are picked up every time
import message_ixis used in Python code. The
[docs,reporting,tests,tutorial]extra requirements ensure additional dependencies are installed.
(Optional) If you will be using
MESSAGE_master.gmsoutside of Python
message_ixto run MESSAGEix, you will likely modify this file, but will not want to commit these changes to Git. Set the Git “assume unchanged” bit for this file:
$ git update-index --assume-unchanged message_ix/model/MESSAGE_master.gms
To unset the bit, use
--no-assume-unchanged. See the Git documentation for more details.
(Optional) If installed from source, run the built-in test suite to check that MESSAGEix functions correctly on your system:
Check that installation was successful
Verify that the version installed corresponds to the latest release by running the following commands on the command line:
# Show versions of message_ix, ixmp, and key dependencies $ message-ix show-versions # Show the list of modelling platforms that have been installed and the path to the database config file # By default, just the local database should appear in the list $ message-ix platform list
The above commands will work as of
message_ix 3.0 and in subsequent versions.
If an error occurs, this may mean that an older version has been installed and should be updated.
To check the current version:
# If installed using conda $ conda list message-ix # If installed using pip $ pip show message-ix
Install R and reticulate
You only need to install R if you want to use
ixmp from R, rather than from Python.
message_ix using one of the three methods above.
Ensure the the R version installed is either 32- or 64-bit (and >= 3.5.0), consistent with GAMS and Java. Having both 32- and 64-bit versions of R, or mixed 32- and 64-bit versions of different packages, can cause errors.
(Optional) Install IRkernel, which allows running R code in Jupyter notebooks (see the link for instructions).
See Usage in R via reticulate for further details.
If you installed
message_ixfrom source, check that the R interface works by using the built-in test suite to run the R tutorial notebooks:
$ pytest -m rmessageix
“No module named ‘pyam’”
The package pyam-iamc is one of the “reporting” extra dependencies of
These extra dependencies are not installed automatically, but can be installed using:
# If message_ix is installed using pip $ pip install message_ix[reporting] # or $ pip install pyam-iamc # If message_ix is installed using Anaconda (see note below) $ conda install pyam
Note that this package has the different name on conda-forge versus PyPI: pyam.
The package listed as pyam on PyPI (and not available via Anaconda) is unrelated to
message_ix, not compatible with it, and will produce other error messages.
If you installed this package accidentally, remove it using:
# If installed using pip $ pip uninstall pyam
Copy GAMS model files for editing
By default, the GAMS files containing the mathematical model core are installed
message_ix (e.g., in your Python
site-packages directory). Many
users will simply want to run MESSAGEix, or use the Python or R APIs to
manipulate data, parameters and scenarios. For these uses, direct editing of the
GAMS files is not necessary.
To edit the files directly—to change the mathematical formulation, such as adding new types of parameters, constraints, etc.—use the
message-ix command-line program to copy the model files in a directory of your choice:
$ message-ix copy-model /path/for/model/files
You can also set the
message model dir configuration key so that this copy of the files is used by default:
$ message-ix config set "message model dir" /path/for/model/files
…or do both in one step:
$ message-ix copy-model --set-default /path/for/model/files