Foam: a general purpose Monte Carlo cellular approach

A self-adapting, general-purpose Monte Carlo (MC) algorithm implemented in the program Foam is described. The high efficiency of the MC, that is small maximum weight or variance of the MC weight is achieved by means of dividing the integration domain into small cells. The cells can be n-dimensional simplices, hyperrectangles or a Cartesian product of them. Cells are produced in the process of the binary split of the cells. The algorithm is able to deal, in principle, with an arbitrary pattern of the singularities in the distribution.