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Modeling and Analysis of Information Systems

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Vol 29, No 1 (2022)
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Algorithms

6-19 571
Abstract
An algorithm of angular superresolution based on the Cholesky decomposition, which is a modification of the Capon algorithm, is proposed. It is shown that the proposed algorithm makes it possible to abandon the inversion of the covariance matrix of input signals. The proposed algorithm is compared with the Capon algorithm by the number of operations. It is established that the proposed algorithm, with a large dimension of the problem, provides some gain both when implemented on a single-threaded and multithreaded computer. Numerical estimates of the performance of the proposed and original algorithm using parallel computing technology CUDA NVidia are obtained. It is established that the proposed algorithm saves GPU computing resources and is able to solve the problem of constructing a spatial spectrum with an increase in the dimension of the covariance matrix of input signals by almost two times.

Discrete Mathematics in Relation to Computer Science

20-29 494
Abstract

Numerical study of various processes leads to the need of clarification (extensions) of the limits of applicability of computational constructs and modeling tools. For dynamical systems, this question may be related with a generalization of the concept of a derivative, which keeps the used constructions relevant. In this article we introduce the concept of weak local differentiability in a space of Lebesgue integrable functions and consider the consistency of this concept with such fundamental computational constructions as the Taylor expansion and finite differences, as well as properties of functions with a given type of differentiability on a segment. The function f from L₁[a; b] is called S-differentiable at the point x₀ from (a; b), if there are coefficients c and q, for which fx₀x₀+h (f (x) - c - q·(x-x₀)) dx = o(h²). Formulas are found for calculating the coefficients c and q, coefficients c and q, which are conveniently denoted fₛ(x₀) and fₛ ˊ(x₀) respectively. It is shown that if the function f belongs to W₁ⁿ⁻¹[a; b], n is greater than 1, and the function f⁽ⁿ⁻¹⁾ is S-differentiable at the point xₒ from (a; b), then f is approximated by a Taylor polynomial with accuracy o((x-xₒ)ⁿ), and the ratio of Δⁿₕ(f, xₒ) to hⁿ tends to fₛ⁽ⁿ⁾(xₒ) as h tends to 0. Based on the quotient Δⁿₕ (f, ·) and hⁿ, a sequence is built {Ʌₘⁿ [f]} piecewise constant functions subordinate to partitions segment [a; b] into m equal parts. It is shown that for the function f from W₁ⁿ⁻¹[a; b], for which the value is defined f ₛ⁽ⁿ⁾(xₒ), { Ʌₘⁿ [f] (xₒ)} converges to f ⁽ⁿ⁾(xₒ) as m tends to infinity, and for f from Wₚⁿ[a; b] the sequence { Ʌₘⁿ [f] } converges to f⁽ⁿ⁾ in the norm of the space Lₚ [I]. The place of S-differentiability in practical and theoretical terms is determined by its bilateral relations with ordinary differentiability. It is proved that if f belongs to W₁ⁿ⁻¹[I] and the function f⁽ⁿ⁻¹⁾ is uniformly S-differentiable on I, then f belongs to Cⁿ[f]. The constructions are algorithmic in nature and can be applied in numerically computer research of various relevant models.

Software

30-43 509
Abstract
The paper proposes a parallel algorithm for solving the Graph-Subgraph Isomorphism Problem and makes an experimental study of its efficiency. The problem is one of the most famous NP-complete problems. Its solution may be required when solving many practical problems associated with the study of complex structures. We solve the problem in a formulation that requires finding all existing isomorphic substitutions or proving their absence. In view of the high complexity of the problem, it is natural to want to speed up its solution by parallelizing the algorithm.We used the RPM ParLib library, developed by the author, as the main tool to program the algorithm. This library allows us to develop effective applications for parallel computing on a local network under the control of the runtime environment .NET Framework. Thanks to this library, applications have the ability to generate parallel branches of computation directly during program execution and dynamically redistribute work between computing modules. Any language with support of the .NET Framework can be used as a programming language in conjunction with this library. For the numerical experiment, an open database from the Internet was used, which was specially developed to study algorithms for searching for isomorphic substitutions. Also, the author has developed a special application in C# for generating additional sets of initial data with specified characteristics. The aim of the experiment was to study the speedup achieved due to the recursively parallel organization of computations. The paper provides a detailed description of the proposed algorithm, as well as the results obtained during the experiment.

Theory of Computing

44-59 509
Abstract
The article revises the results of the work devoted to the problem of representing the behaviour of a program system as a set of formulas of the linear temporal logic LTL, followed by the use of this representation to verify the satisfiability of the program system properties through the procedure of proving the validity of logical inferences, expressed in terms of the LTL logic. The LTL logic is applied to bounded Minsky counter machines that are considered as program systems of which we need to get the specification of its behaviour. Earlier, when working with the temporal logic LTL as a program logic, a special pseudo-operator was actually introduced to refer to the previous values of variables involved in elementary propositions. Despite the fact that this pseudo-operator is easily implemented in the Cadence SMV verifier when proving the validity of logical LTL-inferences, the classical definition of the LTL logic does not imply its presence. In this article, only binary variables will be used to build an LTL-specification for the behaviour of a bounded counter machine, and tracking of previous values of these variables will be carried out exclusively within the LTL logic itself through the appropriate formulas.
60-72 558
Abstract
In this paper methods for increasing the efficiency of VLSI development based on the method of architecture-independent design are proposed. The route of high-level VLSI synthesis is considered. The principle of constructing a VLSI hardware model based on the functional-flow programming paradigm is stated.The results of the development of methods and algorithms for transformation functional-parallel programs into programs in HDL languages that support the design process of digital chips are presented. The principles of assessment are considered and the classes of resources required for the analysis of design solutions are identified. Reduction coefficients and methods of their calculation for each resource class have been introduced. An algorithm for calculating the reduction coefficients and estimating the required resources is proposed. An algorithm for converting parallelism is proposed, taking into account the specified constraints of the target platform. A mechanism for the exchange of metrics with an architecture-dependent level has been developed. Examples of parallelism reduction for the FPGA platform and practical implementation of FFT algorithms in the Virtex® UltraScale FPGA basis are given. The developed methods and algorithms make it possible to use the method of architecture-independent synthesis for transferring VLSI projects to various architectures by changing the parallelism of the circuit and equivalent transformations of parallel programs. The proposed approach provides many options for hardware solutions for implementation on various target platforms.


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ISSN 1818-1015 (Print)
ISSN 2313-5417 (Online)