% Nivio: 29/jan/06 % Time-stamp: \vspace{-2mm} \subsection{The data and the experimental setup} \label{sec:data-exper-set} The algorithms were implemented in the C language and are available at \texttt{http://\-cmph.sf.net} under the GNU Lesser General Public License (LGPL). % free software licence. All experiments were carried out on a computer running the Linux operating system, version 2.6, with a 2.4 gigahertz processor and 1 gigabyte of main memory. In the experiments related to the new algorithm we limited the main memory in 500 megabytes. Our data consists of a collection of 1 billion URLs collected from the Web, each URL 64 characters long on average. The collection is stored on disk in 60.5 gigabytes.