Benchmarks Description Jes´ us Gir´ aldez-Cru *1 and Jordi Levy † 1 1 Artificial Intelligence Research Institute (IIIA-CSIC), Spain Introduction It is accepted that random k-CNF and industrial SAT instances have a distinct na- ture. While random formulas can be easily generated on demand, the set of industrial instances, which encode real-world problems, is limited. The problem of generating real- istic pseudo-industrial random instances is stated in [9, 6, 4] as one of the most important challenges for the next few years. The main motivation of this challenge is improving the process of development and test of SAT solvers, and their possible specialization. Industrial SAT formulas exhibit a clear community structure (i.e. high modularity Q) [1]. This means that, representing formulas as graphs, we can find a partition of the formula into communities with many edges between nodes of the same community (i.e., many clauses relating variables of the same community), and few edges connecting distinct communities. This property is very characteristic in real-world problems in contrast to randomly generated instances, where modularity is very low. In the context of SAT, it has been shown that the community structure is correlated with the runtime of CDCL SAT solvers [8]. Moreover, it has also been used to improve the performance of some solvers [7, 10]. Community Attachment In [5], it is presented a method to generate realistic pseudo-industrial random SAT instances: the Community Attachment model. This generator is based on the com- munity structure, and it generates formulas for any given value of modularity. Therefore, for a high value of modularity, the resulting formula is more adequate to model indus- trial problems than classical random k-CNF. However, it also generates SAT instances similar to the random k-CNF when the value of the modularity is low. The Community Attachment model is parametric in a probability P and a partition C of the set of variables. In this model all variables of a clause belong to the same * jgiraldez@iiia.csic.es † levy@iiia.csic.es 1