Hi list In the context of a scientific project here we are building big matrices for later processing, mostly exporting to custom file formats for PLINK, HaploView, etc (bioinformatics tools). I've tested one of our scripts in both Pharo 1.1 (not CogVM) with the corresponding Python 2.6 implementation (without PyPy), and the performance in Python was superior, about 8x faster than ST. So I wonder if anyone knows the fastest (or a faster) implementation of Matrix than the included by default in Collections? Cheers, -- Hernán Morales Information Technology Manager, Institute of Veterinary Genetics. National Scientific and Technical Research Council (CONICET). La Plata (1900), Buenos Aires, Argentina. Telephone: +54 (0221) 421-1799. Internal: 422 Fax: 425-7980 or 421-1799.