Volume 42, Nº 1 (2016)

Algebraic models of programs with procedures extend algebraic models of programs that are free of procedures (simple models of programs). A specific feature of both types of models is that they are built for some formalization of software programs. Models of programs are intended for studying functional equivalence of formalized programs and constructing wide sets of equivalent transformations of programs. Two basic problems in the theory of algebraic models of programs are the equivalence problem and the problem of building complete systems of equivalent transformations. An increasing interest in models of programs with procedures is due to the abundance of results obtained for simple models of programs. The most suitable model of programs with procedures is a gateway model. A remarkable feature of these models is that every such model is induced by some simple model of programs. This paper gives a survey of the latest results obtained for gateway models of programs.

One of the important classes of computational problems is problem-oriented workflow applications executed in distributed computing environment. A problem-oriented workflow application can be represented by a directed graph whose vertices are tasks and arcs are data flows. For a problem-oriented workflow application, we can get a priori estimates of the task execution time and the amount of data to be transferred between the tasks. A distributed computing environment designed for the execution of such tasks in a certain subject domain is called problem-oriented environment. To efficiently use resources of the distributed computing environment, special scheduling algorithms are applied. Nowadays, a great number of such algorithms have been proposed. Some of them (like the DSC algorithm) take into account specific features of problem-oriented workflow applications. Others (like Min–Min algorithm) take into account many-core structure of nodes of the computational network. However, none of them takes into account both factors. In this paper, a mathematical model of problem-oriented computing environment is constructed, and a new problem-oriented scheduling (POS) algorithm is proposed. The POS algorithm takes into account both specifics of the problem-oriented jobs and multi-core structure of the computing system nodes. Results of computational experiments comparing the POS algorithm with other known scheduling algorithms are presented.

Optimizing compilers increase the resulting code performance by carrying out a number of code optimization techniques. Profile information assistance for code optimizations gives an opportunity to greatly increase the code performance in some cases. However, the impossibility to provide a representative training execution often leads to the decline in efficiency of profile-dependent code optimizations. This paper investigates the main causes of the performance loss for the one-stage optimization as compared to the profileguided optimization (PGO) and introduces some alternative compilation techniques to reduce this loss. The effectiveness of these techniques is evaluated for a VLIW-architecture Elbrus compiler.

A tool for the static analysis of programs that can detect entities in C and C++ programs, their metrics, and relations between them is considered. The program entities are files, functions, classes, methods, etc., and relations are calls, inheritance, read/write operations of global variables, file inclusion, and aggregation. Methods for the development of such a tool based on the open compiler infrastructure LLVM [1], including the necessary modifications in the Clang compiler [2], and the developed analyzer are described. Results of the tool testing on the Android code are presented.