Journal:Informatica
Volume 7, Issue 3 (1996), pp. 295–310
Abstract
In this paper we consider the problem of solving 3D diffusion problems on distributed memory computers. We present a parallel algorithm that is suitable for the number of processors less or equal 8. The pipelining method is used to enlarge the number of processors till 64. The computational grid decomposition method is proposed for heterogenous clusters of workstations which preserves the load balancing of computers. The numerical results for two clusters of workstations are given.
Journal:Informatica
Volume 7, Issue 3 (1996), pp. 281–294
Abstract
This paper deals with load balancing of parallel algorithms for distributed-memory computers. The parallel versions of BLAS subroutines for matrix-vector product and LU factorization are considered. Two task partitioning algorithms are investigated and speed-ups are calculated. The cases of homogeneous and heterogeneous collections of computers/processors are studied, and special partitioning algorithms for heterogeneous workstation clusters are presented.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 268–274
Abstract
Multidimensional scaling (MDS) is well known technique for analysis of multidimensional data. The most important part of implementation of MDS is minimization of STRESS function. The convergence rate of known local minimization algorithms of STRESS function is no better than superlinear. The regularization of the minimization problem is proposed which enables the minimization of STRESS by means of the conjugate gradient algorithm with quadratic rate of convergence.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 255–267
Abstract
Recurrent neural networks of binary stochastic units with a general distribution function are studied using Markov chains theory. Sufficient conditions for ergodicity are established and under some assumptions, the stationary distribution is determined. The relation between fixed points and absorbing states is studied both theoretically and through simulations. For numerical studies the notion of almost absorbing state is introduced.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 229–254
Abstract
This paper is devoted to the consideration of the evolution of the non-migrating limited panmiction population taking into account the size, sex and age structure, pregnancy and females restoration period after delivery. The unique solvability of this model and the condition for the population to vanishe is obtained.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 175–228
Abstract
The paper describes the use of adaptive and non-periodic sampling in different fields of System Theory and Control. The review is organized in a very comprehensive way and it presents results of the last thirty years about the problem of signal applications using as main tool adaptive sampling schemes including results is the improvement of the transient behaviors. Also, related results are presented about the use of non-periodic sampling in compensation as an alternative design to the well-known frequency domain methods and about the choice of the sampling points in order to improve the transmission of measuring and/or rounding errors towards the results when studying the properties of dynamic systems such as controllability, observability and identifiability.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 167–174
Abstract
We consider a stochastic algorithm of optimization in the presented paper. We deal here with the average results of a “mixture” of the deterministics heuristics algorithm and uniform random search. We define the optimal “mixture”.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 155–166
Abstract
Weak approximation methods for initial value problem for the parabolic equation are considered. We propose some simple tests to investigate the quality of RNG used in Monte-Carlo simulations. Numerical examples are given to illustrate the application of stochastic approximation methods.
Journal:Informatica
Volume 7, Issue 2 (1996), pp. 137–154
Abstract
There exist two principally different approaches to design the classification rule. In classical (parametric) approach one parametrizes conditional density functions of the pattern classes. In a second (nonparametric) approach one parametrizes a type of the discriminant function and minimizes an empirical classification error to find unknown coefficients of the discriminant function. There is a number of asymptotic expansions for an expected probability of misclassification of parametric classifiers. Error bounds exist for nonparametric classifiers so far. In this paper an exact analytical expression for the expected error EPN of nonparametric linear zero empirical error classifier is derived for a case when the distributions of pattern classes are spherically Gaussian. The asymptotic expansion of EPN is obtained for a case when both the number of learning patterns N and their, dimensionality p increase infinitely. The tables for exact and approximate expected errors as functions of N, dimensionality p and the distance δ between pattern classes are presented and compared with the expected error of the Fisher's linear classifier and indicate that the minimum empirical error classifier can be used even in cases where dimensionality exceeds the number of learning examples.
Journal:Informatica
Volume 7, Issue 1 (1996), pp. 97–130
Abstract
The goal of this work is to describe the underlying theoretical and algorithmic basis of a MATLAB-based software developed by the authors. The software is intended for investigation of time series (signals) which can be modeled as the sum of real-valued quasipolynomials plus white noise. With the help of the software described, one can compute the expressions of the Cramér-Rao lower bound on the covariance matrix of the estimation error of unbiased estimates of damping factors and frequencies of quasipolynomials and to obtain estimates of these parameters using three versions of Prony method. Using this software, one can generate various models of quasipolynomials, obtain plots of their poles with respect to the unit circle, compute and plot 2σ-bounds (where σ is given by the CRB formula) around each pole, and also pole estimates obtained in each realization. Results of numerical experiments are presented.