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libsharp-wrapper

A Python wrapper for the libsharp library

Summary

Description

The libsharp-wrapper is a Python wrapper for the C-library libsharp. It is written in Cython and C++. The functional layout is inspired by healpy.

The wrapper provides access to the spherical harmonics transformation of the Gauss-Legendre pixelization. An extension to all pixelizations supported by libsharp would be feasible.

Features

  • Spherical harmonics transformations from and to the Gauss-Legendre pixelization:

    alm2map()          map2alm()
alm2map_f()        map2alm_f()

  • Support for NumPy arrays in double and float precision (functions operating on floats are suffixed by _f)

  • Power spectrum analysis and field synthesis (assuming statistically homogeneous and isotropic random fields):

    anaalm()           anafast()          synalm()          synfast()
anaalm_f()         anafast_f()        synalm_f()        synfast_f()

  • Smoothing with Gaussian kernel:

    smoothalm()        smoothmap()

  • Support functions for pixelization issues:

    bounds()           weight()
vol()              weight_f()

  • Support functions for geometrical quantities and indices:

    ang2pix()          ang2xyz()          pix2xyz()         lm2i()
pix2ang()          xyz2ang()          xyz2pix()         i2lm()
pix2nn()

  • Non-trivial scalar product in spherical harmonics basis:

    dotlm()            dotlm_f()

Installation

Requirements

... for libsharp

  • GNU make
  • GNU gcc (v4.x)
  • GNU autoconf
  • git

... for libsharp-wrapper

  • Cython (v0.1x)
  • Python (v2.7.x)
  • Python Development Tools
  • Numpy
  • Numpy Development Tools

Compilation

... of libsharp

git clone git://git.code.sf.net/p/libsharp/code libsharp-code
cd libsharp-code
autoconf
configure --enable-pic --disable-openmp
make
cd ..

... of libsharp-wrapper

git clone git://github.com/mselig/libsharp-wrapper.git libsharp-wrapper
cd libsharp-wrapper
python setup.py build_ext

Installation

python setup.py install

Alternatively, a private or user specific installation can be done by:

python setup.py install --user
python setup.py install --install-lib=/SOMEWHERE

Test

In Python run:

>>> import numpy as np
>>> import libsharp_wrapper_gl as gl
>>> gl.map2alm(np.ones(28), nlat=4, nlon=7, lmax=3, mmax=3)[0]**2 # == 4 pi
(12.566370614359174+0j)

Release Notes

The libsharp-wrapper is licensed under the GPLv2 and is distributed without any warranty.

The current version is tagged v0.2.0 and is available as a source package at https://github.com/mselig/libsharp-wrapper/tags.