Statistical models to accelerate software development by means of iterative compilation

Minimization of data-processing time and reduction of software-development time are important practical problems to be tackled by modern computer science.This paper presents the authors' proposal of a family of statistical models for the estimation of program execution time, which is an approach focused on both of the above problems at the same time. The family consists of a general model and specific models and has been elaborated based on empirical data collected for pattern-program loops representing some arbitrarily selected features related to the program structure and the specificity of a program-execution environment.The paper presents steps to elaborate the aforementioned family as well as the results of the carried-out experimental research. The paper demonstrates how the elaborated models can be applied in iterative compilation for optimization purposes, allowing us to reduce the time of software development and produce code with minimal execution time

Dynamic Tile Free Scheduling for Code with Acyclic Inter-Tile Dependence Graphs

Free scheduling is a task ordering technique under which instructions are executedas soon as their operands become available. Coarsening the grain ofcomputations under the free schedule, by means of using groups of loop neststatement instances (tiles) in place of single statement instances, increases thelocality of data accesses and reduces the number of synchronization events, andas a consequence improves program performance. The paper presents an approachfor code generation allowing for the free schedule for tiles of arbitrarilynested affine loops at run-time. The scope of the applicability of the introducedalgorithms is limited to tiled loop nests whose inter-tile dependence graphs arecycle-free. The approach is based on the Polyhedral Model. Results of experimentswith the PolyBench benchmark suite, demonstrating significant tiledcode speed-up, are discussed

Państwo i społeczeństwo wobec chaosu przestrzennego - źródła i działania: Dyskusja redakcyjna

The following debate took place on March 22, 2019 at the Warsaw School of Economics. The content of the Study on Spatial Chaos report provided the framework for the discussion. Its authors estimated the cost of spatial chaos at PLN 84.3 billion per year. They indicated the main mechanisms leading to the occurrence of this phenomenon

Parallel Tiled Code for Computing General Linear Recurrence Equations

In this article, we present a technique that allows us to generate parallel tiled code to calculate general linear recursion equations (GLRE). That code deals with multidimensional data and it is computing-intensive. We demonstrate that data dependencies available in an original code computing GLREs do not allow us to generate any parallel code because there is only one solution to the time partition constraints built for that program. We show how to transform the original code to another one that exposes dependencies such that there are two linear distinct solutions to the time partition restrictions derived from these dependencies. This allows us to generate parallel 2D tiled code computing GLREs. The wavefront technique is used to achieve parallelism, and the generated code conforms to the OpenMP C/C++ standard. The experiments that we conducted with the resulting parallel 2D tiled code show that this code is much more efficient than the original serial code computing GLREs. Code performance improvement is achieved by allowing parallelism and better locality of the target code

Application of Statistical Models to Select Tile Size Minimizing the Execution Time of Parallelized Tiled Loop Nests

The reduction of software development time is an important practical problem to be dealt with by contemporary computer science. Resolving this problem is an object of research carried out both in scientific and industrial centres. One of the main areas of this research is compilation. Within compilation, a computer program written in a programming language comprehensible for a man is converted into an executable form comprehensible for a computer. Applying appropriately selected transformations (tiling also known as blocking) during compilation, one can transform a program, written in a given programming language and for a given hardware platform, to various yet semantically equivalent executables which however differ in execution times. The paper presents a statistical model which allows for selecting from semantically equivalent, tiled source code variants of a given program the variants with best anticipated execution times. The paper also demonstrates how the elaborated model can be applied in iterative compilation for shortening software development time

Tiling arbitrarily nested loops by means of the transitive

A novel approach to generation of tiled code for arbitrarily nested loops is presented. It is derived via a combination of the polyhedral and iteration space slicing frameworks. Instead of program transformations represented by a set of affine functions, one for each statement, it uses the transitive closure of a loop nest dependence graph to carry out corrections of original rectangular tiles so that all dependences of the original loop nest are preserved under the lexicographic order of target tiles. Parallel tiled code can be generated on the basis of valid serial tiled code by means of applying affine transformations or transitive closure using on input an inter-tile dependence graph whose vertices are represented by target tiles while edges connect dependent target tiles. We demonstrate how a relation describing such a graph can be formed. The main merit of the presented approach in comparison with the well-known ones is that it does not require full permutability of loops to generate both serial and parallel tiled codes; this increases the scope of loop nests to be tiled

Tiling arbitrarily nested loops by means of the transitive

A novel approach to generation of tiled code for arbitrarily nested loops is presented. It is derived via a combination of the polyhedral and iteration space slicing frameworks. Instead of program transformations represented by a set of affine functions, one for each statement, it uses the transitive closure of a loop nest dependence graph to carry out corrections of original rectangular tiles so that all dependences of the original loop nest are preserved under the lexicographic order of target tiles. Parallel tiled code can be generated on the basis of valid serial tiled code by means of applying affine transformations or transitive closure using on input an inter-tile dependence graph whose vertices are represented by target tiles while edges connect dependent target tiles. We demonstrate how a relation describing such a graph can be formed. The main merit of the presented approach in comparison with the well-known ones is that it does not require full permutability of loops to generate both serial and parallel tiled codes; this increases the scope of loop nests to be tiled

Dyskusja redakcyjna. Państwo i społeczeństwo wobec chaosu przestrzennego - źródła i działania

The following debate took place on March 22, 2019 at the Warsaw School of Economics. The content of the Study on Spatial Chaos report provided the framework for the discussion. Its authors estimated the cost of spatial chaos at PLN 84.3 billion per year. They indicated the main mechanisms leading to the occurrence of this phenomenon.Poniższa debata odbyła się 22 marca 2019 r. w Szkole Głównej Handlowej w Warszawie. Ram do dyskusji dostarczyła treść raportu Studia nad chaosem przestrzennym. Jego autorzy oszacowali koszty występowania chaosu przestrzennego na kwotę 84,3 mld zł rocznie. Wskazali na główne mechanizmy prowadzące do występowania tego zjawiska

Dyskusja redakcyjna. Państwo i społeczeństwo wobec chaosu przestrzennego - źródła i działania

The following debate took place on March 22, 2019 at the Warsaw School of Economics. The content of the Study on Spatial Chaos report provided the framework for the discussion. Its authors estimated the cost of spatial chaos at PLN 84.3 billion per year. They indicated the main mechanisms leading to the occurrence of this phenomenon.Poniższa debata odbyła się 22 marca 2019 r. w Szkole Głównej Handlowej w Warszawie. Ram do dyskusji dostarczyła treść raportu Studia nad chaosem przestrzennym. Jego autorzy oszacowali koszty występowania chaosu przestrzennego na kwotę 84,3 mld zł rocznie. Wskazali na główne mechanizmy prowadzące do występowania tego zjawiska