FLTSS (Fast Legendre Transform with Stable Sampling)

The original FLTSS site has been lost by disk crash. I could recover a part of the original site, specifically of the results of Williamson's shallow water test caes. Sorry that the software itself is not provided now.

FLTSS is a set of routines and data files of fast transform of associated Legendre expansion. It is assumed to be used as a part of fast spherical harmonics transform.

This software is FREE. Please cite our paper when you publish your work using this program or modified one:
R. Suda and M. Takami, "A Fast Spherical Harmonics Transform Algorithm", Math. Comp., Vol. 71, No. 238, Apr. 2002, pp. 703--715.

Results for the Williamson's shallow water test cases are provided.

Now UNavailable:
Language VersionRelease Date
fortran90 0.21 3 Apr. 2003.
FORTRAN77 0.22 8 Apr. 2003.

We are planning:

Do you think it is better to offer separate transform routines for even and odd parts? Or do you accept overwriting the input vector and/or removing the flt_add (add to the output vector) option? Do you think the size of work array is too large? Feel free to tell me your opinion.


The current implementation is basic, and we did not consider about performance tuning for cache, vector or parallel processing. Tuning will be done soon, since performance is essential for FAST transform.


Currently, the fortran program does not include the preprocessing routine, and it reads the preprocessed data from disk.

The preprocessing algorithm is not finished yet, and the preprocessing program will not be released soon. Perhaps it takes one or two years.


Our algorithm may be applicable to other function tranforms. If you have any requirements of large scale function transform, please let us know it.


E-mail: reiji@na.cse.nagoya-u.ac.jp