Software Corner Genetic Algorithm File Fitter (GAFFitter) Douglas A. Augusto, daaugusto@gmail.com Genetic Algorithm File Fitter, GAFFitter for short, is a tool based on a genetic algorithm (GA) that tries to t a collection of items into as few volumes of speci c size as possible. For example, the items might be les and the volumes might be CDs or DVDs. GAFFitter was created with the intent to minimize the number of CDs or DVDs used to store a set of les whose total size is greater than the medium capacity. It was further extended to work directly with any set of items, whether it is composed of les/directories or not. GAFFitter is characterized by ve main features, namely: The global search based on a genetic algorithm. The lter-oriented design, that is, a versatile interface suitable for integration with other tools and front-ends. The possibility to use lenames as the input and to directly read a list of items and their sizes. The great ‚exibility provided by the input arguments, which controls the behaviour of GAFFitter, including many genetic algorithm parameters. The fact that it is a free software, which makes it possible for the users to study, change and redistribute GAFFitter. The current development version of GAFFitter is based on the Falkenauer ™s Hybrid Grouping Genetic Algorithm (HGGA) [1], which is probably one of the best GA approaches for bin packing problems. In the HGGA, the genes represent each one a group of items, i.e., each gene is treated as a bin and their items act as an unit, a building block; therefore, the crossover operator does not mixes items on an individual basis, but, rather, it combines groups of bins. Besides, HGGA uses a local optimizer inspired on the Dominance Criterion of Martello and Toth [1], which basically tries iteratively to replace a few items of a certain bin by fewer items that t better in. This procedure not only optimizes the bin, but also eases the reallocation of the replaced items, since smaller items are easier to t. GAFFitter is written in C++ and is currently available as a command-line program for POSIX-compliant systems (GNU/Linux, BSD derivatives and so on). The simplest way to run GAFFitter is as follows: gaffitter -t 700m * This command will arrange the les and subdirectories of the current directory into sets of at most 700 megabytes (a typical CD), in such a way that the number of sets is minimized. In other words, GAFFitter will try to t the given les and directories into as few as possible volumes of 700MB. A comprehensive description of GAFFitter ™s options and parameters, several usage examples, and instructions on how to get its source code can be found on GAFFitter ™s website at http://gaf tter.sf.net Bibliography [1] E. Falkenauer. A Hybrid Grouping Genetic Algorithm for Bin Packing, 1996. The development version can be fetched from the GAFFitter ™s Subversion repository (see the website). Be aware, however, that the development versions are usually unstable, non-optimized and prone to bugs. SIGEVOlution Spring 2008, Volume 3, Issue 1

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