NIFTy - Numerical Information Field Theory

NIFTy project homepage: http://ift.pages.mpcdf.de/nifty

Summary

Description

NIFTy, "Numerical Information Field Theory", is a versatile library designed to enable the development of signal inference algorithms that operate regardless of the underlying grids (spatial, spectral, temporal, …) and their resolutions. Its object-oriented framework is written in Python, although it accesses libraries written in C++ and C for efficiency.

NIFTy offers a toolkit that abstracts discretized representations of continuous spaces, fields in these spaces, and operators acting on these fields into classes. This allows for an abstract formulation and programming of inference algorithms, including those derived within information field theory. NIFTy's interface is designed to resemble IFT formulae in the sense that the user implements algorithms in NIFTy independent of the topology of the underlying spaces and the discretization scheme. Thus, the user can develop algorithms on subsets of problems and on spaces where the detailed performance of the algorithm can be properly evaluated and then easily generalize them to other, more complex spaces and the full problem, respectively.

The set of spaces on which NIFTy operates comprises point sets, n-dimensional regular grids, spherical spaces, their harmonic counterparts, and product spaces constructed as combinations of those. NIFTy takes care of numerical subtleties like the normalization of operations on fields and the numerical representation of model components, allowing the user to focus on formulating the abstract inference procedures and process-specific model properties.

Installation

Requirements

• Python 3 (3.5.x or later)
• SciPy

Optional dependencies:

• pyHealpix (for harmonic transforms involving domains on the sphere)
• nifty_gridder (for radio interferometry responses)
• mpi4py (for MPI-parallel execution)
• matplotlib (for field plotting)
• pypocketfft (for faster FFTs)

Sources

The current version of NIFTy6 can be obtained by cloning the repository and switching to the NIFTy_6 branch:

git clone https://gitlab.mpcdf.mpg.de/ift/nifty.git

Installation

In the following, we assume a Debian-based distribution. For other distributions, the "apt" lines will need slight changes.

NIFTy6 and its mandatory dependencies can be installed via:

sudo apt-get install git python3 python3-pip python3-dev
pip3 install --user git+https://gitlab.mpcdf.mpg.de/ift/nifty.git@NIFTy_6

Plotting support is added via:

sudo apt-get install python3-matplotlib

Support for spherical harmonic transforms is added via:

pip3 install --user git+https://gitlab.mpcdf.mpg.de/ift/pyHealpix.git

Support for the radio interferometry gridder is added via:

pip3 install --user git+https://gitlab.mpcdf.mpg.de/ift/nifty_gridder.git

MPI support is added via:

sudo apt-get install python3-mpi4py

Pypocketfft is added via: pip3 install --user git+https://gitlab.mpcdf.mpg.de/mtr/pypocketfft

If this library is present, NIFTy will detect it automatically and prefer it over SciPy's FFT. The underlying code is actually the same, but pypocketfft is compiled with optimizations for the host CPU and can provide significantly faster transforms.

Running the tests

To run the tests, additional packages are required:

sudo apt-get install python3-pytest-cov

Afterwards the tests (including a coverage report) can be run using the following command in the repository root:

pytest-3 --cov=nifty6 test

First Steps

For a quick start, you can browse through the informal introduction or dive into NIFTy by running one of the demonstrations, e.g.:

python3 demos/getting_started_1.py

Building the documentation from source

To build the documentation from source, install sphinx and the Read The Docs Sphinx Theme on your system and run

sh docs/generate.sh

Acknowledgements

Please acknowledge the use of NIFTy in your publication(s) by using a phrase such as the following:

"Some of the results in this publication have been derived using the NIFTy package (https://gitlab.mpcdf.mpg.de/ift/NIFTy)"

and a citation to one of the publications.

Licensing terms

The NIFTy package is licensed under the terms of the GPLv3 and is distributed without any warranty.