Armando Palafox Eng. CINVESTAV   Av. Instituto Politécnico Nacional 2508 Col. San Pedro Zacatenco Mexico, DF 07360 México   apalafox@computacion.cs.cinvestav.mx   http://www.cs.cinvestav.mx/Gen2011.html           JEL Areas: C6 : Mathematical Methods and Programming: General C8 : Data Collection and Data Estimation Methodology; Computer Programs: General