isqrt 0.11.0

Efficient native Python implementation of the integer square root function.

Efficient Python implementation of the integer square root function.

Purpose

Given an arbitrarily large non-negative integer n, the integer square root function finds the largest integer r such that r**2 <= n and (r+1)**2 > n. The running time is linear in the bit length of the input integer.

Package Installation and Usage

The package is available on PyPI:

python -m pip install isqrt

The library can be imported in the usual way:

from isqrt import isqrt

The function isqrt is an efficient implementation of the integer square root algorithm:

>>> isqrt(4)
2
>>> isqrt(16)
4
>>> list(map(isqrt, range(16, 26)))
[4, 4, 4, 4, 4, 4, 4, 4, 4, 5]
>>> isqrt(2**30000) == 2**15000
True

Testing and Conventions

All unit tests are executed and their coverage is measured when using nose (see setup.cfg for configution details):

python -m pip install nose coverage
nosetests --cover-erase

Alternatively, all unit tests are included in the module itself and can be executed using doctest:

python isqrt/isqrt.py -v

Style conventions are enforced using Pylint:

python -m pip install pylint
pylint isqrt

Acknowledgments

The initial version of this function was posted on Stack Overflow. A more efficient version was implemented by Alexander Gosselin. The implementation in this package is adapted almost directly from these previous implementations.

Contributions

In order to contribute to the source code, open an issue or submit a pull request on the GitHub page for this library.

Versioning

Beginning with version 0.10.0, the version number format for this library and the changes to the library associated with version number increments conform with Semantic Versioning 2.0.0.