GT4Py: GridTools for Python

Python library for generating high-performance implementations of stencil kernels for weather and climate modeling from a domain-specific language (DSL).

⚡️ Quick Start

GT4Py uses the standard Python packaging method, and can be installed using pip. It is not yet released on PyPI, so users have to point to the git repository to install it.

It is recommended to install the package in a virtual environment.

$ git clone https://github.com/GridTools/gt4py.git && cd gt4py
$ python -m venv venv
$ source venv/bin/activate
$ pip install --upgrade setuptools wheel pip
# For the CUDA backends add the '[cudaXXX]' optional dependency
$ pip install -e ./[cuda117]

There are notebooks in the examples/ directory that can be run using IPython notebooks on Jupyter.

$ pip install jupyterlab matplotlib
$ jupyter-lab

There are two options to run the unit and integration tests in tests/:

1. Use tox: pip install tox && tox -r -e py38-all-cpu.
2. Install the development requirements: pip install -r requirements-dev.txt, then pytest can execute the tests directly.

📖 Description

GT4Py is a Python library for expressing computational motifs as found in weather and climate applications. These computations are expressed in a domain specific language (GTScript) which is translated to high-performance implementations for CPUs and GPUs.

The DSL expresses computations on a 3-dimensional Cartesian grid. The horizontal axes (I, J) are always computed in parallel, while the vertical (K) can be iterated in sequential, forward or backward, order. Cartesian offsets are expressed relative to a center index.

In addition, GT4Py provides functions to allocate arrays with memory layout suited for a particular backend.

The following backends are supported:

• numpy: Pure-Python backend
• gt:cpu_ifirst: GridTools C++ CPU backend using I-first data ordering
• gt:cpu_kfirst: GridTools C++ CPU backend using K-first data ordering
• gt:gpu: GridTools backend for CUDA
• cuda: CUDA backend minimally using utilities from GridTools
• dace:cpu: Dace code-generated CPU backend
• dace:gpu: Dace code-generated GPU backend

🚜 Installation

For testing GT4Py with the numpy backend, all dependencies are included in the setup.cfg and are automatically installed. The performance backends require

1. GridTools which is automatically downloaded on first use,
2. Boost a dependency of GridTools, which needs to be installed by the user.

GridTools will automatically be downloaded when needed by the gt_src_manager.py module. To manually install or uninstall, run:

$ python -m gt4py.gt_src_manager {un}install

Options

If GridTools or Boost are not found in the compiler's standard include path, or a custom version is desired, then a couple configuration environment variables will allow the compiler to use them:

• GT_INCLUDE_PATH: Path to the GridTools installation.
• BOOST_ROOT: Path to a boost installation.

Other commonly used environment variables are:

• CUDA_ARCH: Set the compute capability of the NVIDIA GPU if it is not detected automatically by cupy.
• CXX: Set the C++ compiler.
• GT_CACHE_DIR_NAME: Name of the compiler's cache directory (defaults to .gt_cache)
• GT_CACHE_ROOT: Path to the compiler cache (defaults to ./)

More options and details in config.py.

Documentation

GT4Py uses Sphinx documentation. To build the documentation install the dependencies in requirements-dev.txt

$ pip install -r ./gt4py/requirements-dev.txt

and then build the docs with

$ cd gt4py/docs
$ make html  # run 'make help' for a list of targets

Development

For developing GT4Py we recommend to clone the repository and use an editable installation of GT4Py:

$ git clone https://github.com/gridtools/gt4py.git
$ pip install -e ./     # pip install -e ./[cudaXX] for GPU support
$ pip install -r requirements-dev.txt
$ pre-commit install-hooks

Dependencies for running tests locally and for linting and formatting source are listed in requirements-dev.txt.

⚠️ License

GT4Py is licensed under the terms of the GPLv3.