fdint 1.0

A free, open-source python package for computing Fermi-Dirac integrals.

Fermi-Dirac Integrals (FDINT)

FDINT is a free, open-source python package that provides fast, double precision (64-bit floating point) approximations to the Fermi-Dirac integrals of integer and half integer order, based on the work by Prof. Fukushima [1].

[1]

T. Fukushima, “Precise and fast computation of Fermi-Dirac integral of integer and half integer order by piecewise minimax rational approximation,” Applied Mathematics and Computation, vol. 259, pp. 708-729, May 2015.

The source code and documentation (coming soon) are graciously hosted by GitHub.

Installation

In order to use FDINT, you must having a working Python distribution installed. Python 3 support has not yet been tested, so Python 2.7 is suggested. In order to achieve the highest performance, a Fortran 90 compiler, such as gfortran, is required.

From PyPi

This is the easiest method. Install from PyPi by running the following command:

pip install fdint

From Github

First, you will need to install the following prerequisite packages:

• Numpy

Additional functionality is provided by the following optional packages:

• Matplotlib

Once these are installed, download the latest release .zip or .tar.gz source package from the github page, extract its contents, and run python setup.py install from within the extracted directory.

Testing

Once installed, you can test the package by running the following command:

python -m fdint.tests

If you have Matplotlib installed, you can also plot a sample of the available functions by running the following command:

python -m fdint

Tutorial

First, start up an interactive python shell from the command line:

$ python

Next, import everything from the fdint package:

>>> from fdint import *

If you see the following warning, then the Fortran library failed to compile and/or install:

WARNING: Unable to import fortran module. Falling back to the slower python
module.

The same functionality is provided by the fall-back python module, but the python module is considerably slower. Either way, now you can access the Fermi-Dirac integral, fdk, and the derivative, dfdk, convenience functions:

>>> fdk(k=0.5,phi=-10)
4.0233994366893939e-05
>>> fdk(0.5,-10)
4.0233994366893939e-05
>>> fdk(k=0.5,phi=5)
7.837976057293096
>>> fdk(k=0.5,phi=50)
235.81861512588432
>>> dfdk(k=0.5,phi=-10,d=1)
4.0233348580568672e-05
>>> dfdk(k=0.5,phi=5,d=1)
2.1916282173557855
>>> dfdk(k=0.5,phi=50,d=1)
7.0699026455055112
>>> dfdk(k=0.5,phi=50,d=2)
0.07074571454521902

If you request an order or derivative that is not implemented, a NotImplementedError is raised:

>>> fdk(22,0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "fdint/fdint.py", line 68, in fdk
    raise NotImplementedError()
NotImplementedError
>>> dfdk(k=0.5,phi=50,d=10)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "fdint/fdint.py", line 99, in dfdk
    raise NotImplementedError()
NotImplementedError

If you prefer to call the low-level functions directly, you can access them from the _fd module:

>>> _fd.fd1h(-10)
4.0233994366893939e-05

Documentation

The documentation (coming soon) is graciously hosted by GitHub.