The paper presents a performance model of a network of heterogeneous computers that takes account of the heterogeneity of memory structure and other architectural differences. Under this model, the speed of each processor is represented by a function of the size of the problem whereas standard models use single numbers to represent the speeds of the processors. We prove that this model is more realistic than the standard ones when the network includes computers with significantly different memory structure. We formulate a problem of partitioning of an nelement set over p heterogeneous processors using this advanced performance model and give its efficient solution of the complexity O(p2?log2n).