4,893 research outputs found
MƱszaki informatikai problémåkhoz kapcsolódó diszkrét matematikai modellek vizsgålata = Discrete mathematical models related to problems in informatics
DiszkrĂ©t matematikai mĂłdszerekkel strukturĂĄlis Ă©s kvantitatĂv összefĂŒggĂ©seket bizonyĂtottunk; algoritmusokat terveztĂŒnk, komplexitĂĄsukat elemeztĂŒk. Az eredmĂ©nyek a grĂĄfok Ă©s hipergrĂĄfok elmĂ©letĂ©hez, valamint on-line ĂŒtemezĂ©shez kapcsolĂłdnak. NĂ©hĂĄny kiemelĂ©s: - Pontosan leĂrtuk azokat a szerkezeti feltĂ©teleket, amelyeknek teljesĂŒlni kell ahhoz, hogy egy kommunikĂĄciĂłs hĂĄlĂłzatban Ă©s annak minden összefĂŒggĆ rĂ©szĂ©ben legyen olyan, megadott tĂpusĂș összefĂŒggĆ rĂ©szhĂĄlĂłzat, ahonnan az összes többi elem közvetlenĂŒl elĂ©rhetĆ. (A problĂ©ma kĂ©t Ă©vtizeden ĂĄt megoldatlan volt.) - Aszimptotikusan pontos becslĂ©st adtunk egy n-elemƱ alaphalmaz olyan, k-asokbĂłl ĂĄllĂł halmazrendszereinek minimĂĄlis mĂ©retĂ©re, amelyekben minden k-osztĂĄlyĂș partĂciĂłhoz van olyan halmaz, ami az összes partĂciĂł-osztĂĄlyt metszi. (Nyitott problĂ©ma volt 1973 Ăłta, több szerzĆ egymĂĄstĂłl fĂŒggetlenĂŒl is felvetette.) - Halmazrendszerek partĂciĂłira az eddigieknĂ©l ĂĄltalĂĄnosabb modellt vezettĂŒnk be, megvizsgĂĄltuk rĂ©szosztĂĄlyainak hierarchikus szerkezetĂ©t Ă©s hatĂ©kony algoritmusokat adtunk. (Sok alkalmazĂĄs vĂĄrhatĂł az erĆforrĂĄs-allokĂĄciĂł terĂŒletĂ©n.) - Kidolgoztunk egy mĂłdszert, amellyel lokĂĄlisan vĂ©ges pozĂciĂłs jĂĄtĂ©kok nyerĆ stratĂ©giĂĄja megtalĂĄlhatĂł mindössze lineĂĄris mĂ©retƱ memĂłria hasznĂĄlatĂĄval. - FĂ©lig on-line ĂŒtemezĂ©si algoritmusokat terveztĂŒnk (kĂ©tgĂ©pes feladatra, nem azonos sebessĂ©gƱ processzorokra), amelyeknek versenykĂ©pessĂ©gi arĂĄnya bizonyĂtottan jobb, mint ami a legjobb teljesen on-line mĂłdszerekkel elĂ©rhetĆ. | Applying discrete mathematical methods, we proved structural and quantitative relations, designed algorithms and analyzed their complexity. The results deal with graph and hypergraph theory and on-line scheduling. Some selected ones are: - We described the exact structural conditions which have to hold in order that an intercommunication network and each of its connected parts contain a connected subnetwork of prescribed type, from which all the other nodes of the network can be reached via direct link. (This problem was open for two decades.) - We gave asymptotically tight estimates on the minimum size of set systems of k-element sets over an n-element set such that, for each k-partition of the set, the set system contains a k-set meeting all classes of the partition. (This was an open problem since 1973, raised by several authors independently.) - We introduced a new model, more general than the previous ones, for partitions of set systems. We studied the hierarchic structure of its subclasses, and designed efficient algorithms. (Many applications are expected in the area of resource allocation.) - We developed a method to learn winning strategies in locally finite positional games, which requires linear-size memory only. - We designed semi-online scheduling algorithms (for two uniform processors of unequal speed), whose competitive ratio provably beats the best possible one achievable in the purely on-line setting
Energy consumption in networks on chip : efficiency and scaling
Computer architecture design is in a new era where performance is increased by replicating processing cores on a chip rather than making CPUs larger and faster. This design strategy is motivated by the superior energy efficiency of the multi-core architecture compared to the traditional monolithic CPU. If the trend continues as expected, the number of cores on a chip is predicted to grow exponentially over time as the density of transistors on a die increases. A major challenge to the efficiency of multi-core chips is the energy used for communication among cores over a Network on Chip (NoC). As the number of cores increases, this energy also increases, imposing serious constraints on design and performance of both applications and architectures. Therefore, understanding the impact of different design choices on NoC power and energy consumption is crucial to the success of the multi- and many-core designs. This dissertation proposes methods for modeling and optimizing energy consumption in multi- and many-core chips, with special focus on the energy used for communication on the NoC. We present a number of tools and models to optimize energy consumption and model its scaling behavior as the number of cores increases. We use synthetic traffic patterns and full system simulations to test and validate our methods. Finally, we take a step back and look at the evolution of computer hardware in the last 40 years and, using a scaling theory from biology, present a predictive theory for power-performance scaling in microprocessor systems
Parallelizing RRT on large-scale distributed-memory architectures
This paper addresses the problem of parallelizing the Rapidly-exploring Random Tree (RRT) algorithm on large-scale distributed-memory architectures, using the Message Passing Interface. We compare three parallel versions of RRT based on classical parallelization schemes. We evaluate them on different motion planning problems and analyze the various factors influencing their performance
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