The Wayback Machine - https://web.archive.org/web/20100623034953/http://www.math.ohiou.edu/~mjm/research/libftsh.html

$Ohio University$

libftsh: software for a fast transform for spherical harmonics

Algorithm and code by Martin J. Mohlenkamp.

Originally released October 2000.
University of Colorado APPM preprint number 474, October 2001.
Available at www.math.ohiou.edu/~mjm/libftsh.html.

This library of C routines implements a fast transform for spherical harmonics. It is free under the terms of the GNU General Public License.

Notes:

It is not a simple, user-friendly program for the spherical harmonic novice.
It is not for small sizes. Consider it only for degrees greater than 100.
It is an approximate algorithm, but can be tuned to the desired accuracy.
It is numerically stable, and can be used at large degrees/orders and at high precision.
It is not the full transform. It only does the hard part, which is the Associated Legendre Transform portion. By not doing the easy part, it allows the user greater flexibility.

Future Work

Implementation of the version of the algorithm that is asymptotically faster, but has a higher break-even point.
Addition of FORTRAN wrappers, so these routines can be incorporated into existing codes.
Allow initialization in double precision and then running in single precision, thereby allowing transforms that are effectively exact in single precision.

Download

The library is available in a Subversion repository. You can look at files via the web interface, but the best way is using subversion. The command is

svn checkout https://www.math.ohiou.edu/repos/libftsh/trunk/ libftsh

If you wish to be informed of bugs or future releases, or have any questions or comments, send email to mjm@math.ohiou.edu.

Martin J. Mohlenkamp

Last modified: Wed Jan 24 12:25:07 EST 2007

May	JUN	Jul
	23
2008	2010	2011