9 research outputs found
Műszaki informatikai problémákhoz kapcsolódó diszkrét matematikai modellek vizsgálata = Discrete mathematical models related to problems in informatics
DiszkrĂ©t matematikai mĂłdszerekkel strukturális Ă©s kvantitatĂv összefĂĽggĂ©seket bizonyĂtottunk; algoritmusokat terveztĂĽnk, komplexitásukat elemeztĂĽk. Az eredmĂ©nyek a gráfok Ă©s hipergráfok elmĂ©letĂ©hez, valamint on-line ĂĽtemezĂ©shez kapcsolĂłdnak. NĂ©hány kiemelĂ©s: - Pontosan leĂrtuk azokat a szerkezeti feltĂ©teleket, amelyeknek teljesĂĽlni kell ahhoz, hogy egy kommunikáciĂłs hálĂłzatban Ă©s annak minden összefĂĽggĹ‘ rĂ©szĂ©ben legyen olyan, megadott tĂpusĂş összefĂĽggĹ‘ rĂ©szhálĂłzat, ahonnan az összes többi elem közvetlenĂĽl elĂ©rhetĹ‘. (A problĂ©ma kĂ©t Ă©vtizeden át megoldatlan volt.) - Aszimptotikusan pontos becslĂ©st adtunk egy n-elemű alaphalmaz olyan, k-asokbĂłl állĂł halmazrendszereinek minimális mĂ©retĂ©re, amelyekben minden k-osztályĂş partĂciĂłhoz van olyan halmaz, ami az összes partĂciĂł-osztályt metszi. (Nyitott problĂ©ma volt 1973 Ăłta, több szerzĹ‘ egymástĂłl fĂĽggetlenĂĽl is felvetette.) - Halmazrendszerek partĂciĂłira az eddigieknĂ©l általánosabb modellt vezettĂĽnk be, megvizsgáltuk rĂ©szosztályainak hierarchikus szerkezetĂ©t Ă©s hatĂ©kony algoritmusokat adtunk. (Sok alkalmazás várhatĂł az erĹ‘forrás-allokáciĂł terĂĽletĂ©n.) - Kidolgoztunk egy mĂłdszert, amellyel lokálisan vĂ©ges pozĂciĂłs játĂ©kok nyerĹ‘ stratĂ©giája megtalálhatĂł mindössze lineáris mĂ©retű memĂłria használatával. - FĂ©lig on-line ĂĽtemezĂ©si algoritmusokat terveztĂĽnk (kĂ©tgĂ©pes feladatra, nem azonos sebessĂ©gű processzorokra), amelyeknek versenykĂ©pessĂ©gi aránya bizonyĂtottan jobb, mint ami a legjobb teljesen on-line mĂłdszerekkel elĂ©rhetĹ‘. | 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
Geometric, Algebraic, and Topological Combinatorics
The 2019 Oberwolfach meeting "Geometric, Algebraic and Topological Combinatorics"
was organized by Gil Kalai (Jerusalem), Isabella Novik (Seattle),
Francisco Santos (Santander), and Volkmar Welker (Marburg). It covered
a wide variety of aspects of Discrete Geometry, Algebraic Combinatorics
with geometric flavor, and Topological Combinatorics. Some of the
highlights of the conference included (1) Karim Adiprasito presented his
very recent proof of the -conjecture for spheres (as a talk and as a "Q\&A"
evening session) (2) Federico Ardila gave an overview on "The geometry of matroids",
including his recent extension with Denham and Huh of previous work of Adiprasito, Huh and Katz