
NFFT-Lanczos-Example Version 1.0, 15.08.2018

NNFT-Lanczos-Example is a collection of MATLAB code that exemplarily implements 
the "NFFT-Lanczos" method from [1] based on the NFFT3 toolbox, which has to be 
installed separately. It consists of the following files:

README
 - this file.
COPYING
 - A copy of the GPL v2 license.
fastsumAdjacencySetup.m
 - MATLAB code to setup fast evaluation of matrix-vector products with the graph
   adjacency matrix or its normalized version using the NFFT3 toolbox.
fastsumAdjacencyEigs.m
 - MATLAB code to approximate the largest eigenvalues of a graph adjacency matrix
   based on fastsumAdjacencySetup.m and MATLAB's EIGS function.
MinimalExample.m
 - A short MATLAB script that creates a simple data set and performs clustering
   based on the Fiedler vector.

For all MATLAB source files, please refer to the descriptions inside the files
for further information.


REFERENCE
 [1] - D. Alfke, D. Potts, M. Stoll, T. Volkmer - NFFT meets Krylov methods: Fast 
       matrix-vector products for the graph Laplacian of fully connected networks
       (2018). Preprint available at https://arxiv.org/abs/1808.04580

PREREQUISITES
 - This software has been tested in MATLAB R2018a, but it should run in older 
   versions as well.
 - The NFFT3 toolbox with MATLAB access must be available on your system and the
   folder %NFFT-MAIN%/matlab/fastsum must be on your MATLAB path.
   Installation instructions:
   - Download and unpack the toolbox from 
       https://www-user.tu-chemnitz.de/~potts/nfft/
   - Run the 'configure' script with option
       --with-matlab=/PATH/TO/MATLAB/HOME/FOLDER.
     Other useful options are --enable-openmp (for multicore support) and
     possibly --enable-all (only if you plan to use the toolbox for other
     applications besides NFFT-Lanczos).
   - Run 'make' and optionally 'make check'.
   - Add the folder %NFFT-MAIN%/matlab/fastsum to your MATLAB path every time
     before you run MATLAB code from this example.

LICENSE
 - This software is distributed under the GNU General Public License v2. See 
   COPYING for the full license text. If that file is not available, see 
   <http://www.gnu.org/licenses/>.


AUTHORS
 - Dominik Alfke, TU Chemnitz, dominik.alfke(at)mathematik.tu-chemnitz.de
 - Toni Volkmer, TU Chemnitz, toni.volkmer(at)mathematik.tu-chemnitz.de
