NESTML: The NEST Modelling Language

NESTML is a domain-specific language that supports the specification of neuron models in a precise and concise syntax, based on the syntax of Python. Model equations can either be given as a simple string of mathematical notation or as an algorithm written in the built-in procedural language. The equations are analyzed by the associated toolchain, written in Python, to compute an exact solution if possible or use an appropriate numeric solver otherwise.

Directory structure

models - Example neuron models in NESTML format.

pynestml - The source code of the PyNESTML toolchain.

tests - A collection of tests for testing of the toolchain's behavior.

doc - The documentation of the modeling language NESTML as well as processing toolchain PyNESTML.

extras - Miscellaneous development tools, editor syntax highlighting rules, etc.

Installing NESTML

Please note that only Python 3 is supported. The instructions below assume that python is aliased to or refers to python3, and pip to pip3.

Installing the latest release from PyPI

The easiest way to install NESTML is to use the Python Package Index (PyPI). This requires the Python package management system pip to be installed. In Ubuntu, Mint and Debian Linux you can install pip as follows:

sudo apt install python3-pip

NESTML can then be installed into your local user directory via:

pip install nestml --user

Installing the latest development version from GitHub

To obtain the latest development version, clone directly from the master branch of the GitHub repository:

git clone https://github.com/nest/nestml

Install into your local user directory using:

cd nestml
python setup.py install --user

Testing

After installation, correct operation can be tested by:

python setup.py test

Running NESTML

After the installation, the toolchain can be executed by the following command.

nestml ARGUMENTS

where arguments are:

Command	Description
-h or --help	Print help message.
--input_path	Path to the source file or directory containing the model.
--target_path	(Optional) Path to target directory where generated code will be written into. Default is target, which will be created in the current working directory if it does not yet exist.
--target	(Optional) The name of the target platform to generate code for. Default is NEST.
--logging_level	(Optional) Sets the logging level, i.e., which level of messages should be printed. Default is ERROR, available are [INFO, WARNING, ERROR, NO]
--module_name	(Optional) Sets the name of the module which shall be generated. Default is the name of the directory containing the models. The name has to end in "module". Default is nestmlmodule.
--store_log	(Optional) Stores a log.txt containing all messages in JSON notation. Default is OFF.
--dev	(Optional) Enable development mode: code generation is attempted even for models that contain errors, and extra information is rendered in the generated code. Default is OFF.

Generated artifacts are copied to the selected target directory (default is target). In order to install the models into NEST, the following commands have to be executed from within the target directory:

cmake -Dwith-nest=<nest_install_dir>/bin/nest-config .
make all
make install

where <nest_install_dir> is the installation directory of NEST (e.g. /home/nest/work/nest-install). Subsequently, the module can either be linked into NEST (see Writing an extension module), or loaded dynamically using the Install API function. For example, to dynamically load a module with module_name = nestmlmodule in PyNEST:

nest.Install("nestmlmodule")

PyNESTML is also available as a component and can therefore be used from within other Python tools and scripts. After PyNESTML has been installed, the following modules have to be imported:

from pynestml.frontend.pynestml_frontend import to_nest, install_nest

Subsequently, it is possible to call PyNESTML from other Python tools and scripts via:

to_nest(input_path, target_path, logging_level, module_name, store_log, dev)    

This operation expects the same set of arguments as in the case of command line invocation. The following default values are used, corresponding to the command line defaults. Possible values for logging_level are the same as before ('INFO', 'WARNING', 'ERROR', 'NO'). Note that only the path argument is mandatory:

Argument	Type	Default
input_path	string	no default
target_path	string	None
logging_level	string	'ERROR'
module_name	string	nestmlmodule
store_log	boolean	False
dev	boolean	False

If no errors occur, the output will be generated into the specified target directory. In order to avoid an execution of all required module-installation routines by hand, PyNESTML features a function for an installation of NEST models directly into NEST:

install_nest(models_path, nest_path)

Here, models_path should be set to the target directory of to_nest(), and nest_path points to the directory where NEST is installed (e.g., /home/nest/work/nest-install).

A typical script, therefore, could look like the following. For this example, we assume that the name of the generated module is nestmlmodule.

from pynestml.frontend.pynestml_frontend import to_nest, install_nest

to_nest(input_path="/home/nest/work/pynestml/models", target_path="/home/nest/work/pynestml/target")

install_nest("/home/nest/work/pynestml/target", "/home/nest/work/nest-install")

nest.Install("nestmlmodule")
...
nest.Simulate(400.0)

Further reading

For an in-depth introduction to the underlying modeling language NESTML, please refer to the NESTML language documentation.

For those interested in the implementation of PyNESTML or the general structure of a DSL-processing toolchain, please refer to the PyNESTML documentation.

Publications

• Inga Blundell, Dimitri Plotnikov, Jochen Martin Eppler and Abigail Morrison (2018) Automatically selecting a suitable integration scheme for systems of differential equations in neuron models. Front. Neuroinform. doi:10.3389/fninf.2018.00050. Preprint available on Zenodo.

• Konstantin Perun, Bernhard Rumpe, Dimitri Plotnikov, Guido Trensch, Jochen Martin Eppler, Inga Blundell and Abigail Morrison (2018). Reengineering NestML with Python and MontiCore (Version 2.4). Zenodo. doi:10.5281/zenodo.1319653.

• Dimitri Plotnikov, Bernhard Rumpe, Inga Blundell, Tammo Ippen, Jochen Martin Eppler and Abigail Morrison (2016). NESTML: a modeling language for spiking neurons. In Modellierung 2016, March 2-4 2016, Karlsruhe, Germany. 93–108. doi:10.5281/zenodo.1412345.