[en] Optimization processes leading to computer time savings may be divided into general which can be applied independently of the problem and specific which depend on the characteristics of the problem to be solved. Data files must be prepared and standardized such as to contain direct values used in the modelling algorithm to eliminate subsequent operations with data in the course of the actual computation. It may be favourable to sort data in descending sequence of energies. It is desirable to select an algorithm which in tabulated values should identify the sought value with the smallest number of steps. Considerable time savings may be achieved by the use of a general algorithm of generating random numbers with analytically or tabularly pre-defined distribution; the algorithm is based on approximation of the distribution function. An example is presented of specific optimization procedures for modelling spectra of energy deposited by primary photons in a homogeneous cylindrical detector by the method of grouped collisions. (M.D.)