Section: Software

CADO-NFS

Participants : Cyril Bouvier, Jérémie Detrey, Alain Filbois, Pierrick Gaudry, Alexander Kruppa, Emmanuel Thomé [contact] , Paul Zimmermann.

Cado-nfs is a program to factor integers using the Number Field Sieve algorithm (NFS), originally developped in the context of the ANR-CADO project (November 2006 to January 2010).

NFS is a complex algorithm which contains a large number of sub-algorithms. The implementation of all of them is now complete, but still leaves some places to be improved. Compared to existing implementations, the Cado-nfs implementation is already a reasonable player. Several factorizations have been completed using our implementations.

Since 2009, the source repository of Cado-nfs is publicly available for download. No new release was made in 2012, but several improvements have been made in the development version, with the help of Alain Filbois (SED engineer) and of Alexander Kruppa, recruited in October for a 2-year engineer contract.

Alain Filbois improved the purge program for filtering, by gaining a factor of about 5 in the input-output routines. Together with P. Zimmermann, he also wrote a special-purpose clique removal code for huge factorizations requiring out-of-core computing; this code has been used for a new filtering experiment on the relations collected for RSA-768 (not yet finished at the time of writing).

The Objectif 1024 ADT started in 2012, with the recruitment of Alexander Kruppa as a engineer for 2 years. The four main objectives of this ADT are: (1) be able to use Cado-nfs routinely on clusters of 20 to 100 nodes, including on Amazon EC2; (2) develop precise tools to optimize parameters in the sieving phase; (3) develop more professional test mechanisms; (4) make two major releases of Cado-nfs , and advertize them on potential users.

Overall, Cado-nfs keeps improving its competitivity over alternative code bases. Improvements in Cado-nfs and new results obtained with Cado-nfs are described below.