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Hierarchical compression
Kreibichová, Lenka ; Lánský, Jan (advisor) ; Dvořák, Tomáš (referee)
The most of existing text compression methods is based on the same base concept. First the Input text is divided into sequence of text units. These text units cat be single symbols, syllables or words. When compressing large text files, searching for redundancies over longer text units is usually more effective than searching over the shorter ones. But if we choose words as base units we cannot anymore catch redundancies over symbols and syllables. In this paper we propose a new text compression method called Hierarchical compresssion. It constructs hierarchical grammar to store redundancies over syllables, words and upper levels of text. The code of the text then consists of code of this grammer. We proposed a strategy for constructing hierarchical grammar for concrete input text and we proposed an effective way how to encode it. Above mentioned our proposed method is compared with some other common methods of text compression.
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Mapping of Match Tables from P4 Language to FPGA Technology
Kekely, Michal ; Matoušek, Jiří (referee) ; Kořenek, Jan (advisor)
This thesis deals with design and implementation of mapping of match action tables from P4 language to FPGA technology. Goal of the thesis was to describe key principles, which need to be understood in order to design such a mapping and function of algorithms needed, apply these principles by implementing them and analyze the speed and memory requirements of such an implementation. Outcome provides configurable hardware unit capable of classifying packets and connection between the unit and match action tables from P4 language. The implementation is based on DCFL algorithm and requires less memory compared to HiCuts and HyperCuts algorithms while being comparably fast at worst-case scenarios.
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Longest Prefix Match Algorithms
Skačan, Martin ; Puš, Viktor (referee) ; Tobola, Jiří (advisor)
This bachelor's thesis deals with the algorithms for longest prefix match (LPM), which is the basic operation of the packet classification and of the routing in the IP computer networks. It is introduced the necessary theory and the analysis of the chosen algorithms - Trie, Tree Bitmap, Shape Shifting Tree and Multi-match. These methods were closely described and they were implemented in the programming language Python. Within the implemented algorithms were performed tests and simulations considering their memory demands with the aim to identify the best method for prefix collections about the size of tens to thousands rules.
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Longest Prefix Match Algorithms
Sedlář, František ; Puš, Viktor (referee) ; Tobola, Jiří (advisor)
This bachelor's thesis deals with a description of basic longest prefix match (LPM) algorithms. Another algorithm - LC Trie - was added to existing implementations into the Netbench library. All the algorithms which the library includes were tested with real groups of IPv6 prefixes. They were compared on the basis of previously obtained data. Testing scripts for each of the algorithms were implemented as well as scripts for downloading groups of prefixes from significant sources on the internet.
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Compression Methods Based on Context Modelling
Gach, Tomáš ; Drábek, Vladimír (referee) ; Bařina, David (advisor)
The aim of this thesis is to describe basic properties of the context-based compression methods. Modelling procedure is presented together with the principle of an arithmetic coding. Gradually the PPM, CTW, and PAQ methods are introduced together with the possible implementation of the basic PPM probability model. The performance of context-based, dictionary and the most currently used methods of data compression is being compared. Based on obtained results, the possible usage of PPM methods is summarized.
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Detection of Dynamic Network Applications
Juránek, Michal ; Kaštil, Jan (referee) ; Tobola, Jiří (advisor)
This thesis describes methods of detection of simple voice communications of encrypted VoIP calls between two Skype clients. The elements of network and its communication principles are described. Three approaches to classification are analyzed. The first approach performs the classification by content of network packets using Pearson's chi2 test of goodness of fit, the second approach by characteristics of network flows by means of naive Bayesian classification. The third approach describes ways of detecting signaling messages. The detector application is implemented on the basis of chosen methods.
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Morphological Analyser Implemented as FSAs
Černý, Stanislav ; Černocký, Jan (referee) ; Smrž, Pavel (advisor)
We describe morphemic analyser using dictionary approach. Dictionary is saved as deterministic finite state automata. Another part of text deals with analysis of numerals, especially retrieving numeric value from that words. Besides the analysis there is description of generating word-formation relationships in this work.
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Scrabble for Mobil Phones
Kaněčka, Ondřej ; Kunc, Michael (referee) ; Schönecker, Rudolf (advisor)
This paper deals with an usage of searching algorithms and lexical data structures for platforms with limited computing power and accessible memory (celluar phones and similar) in SCRABBLE brand crossword game. There are also shown its advantages and disadvantages on this platform. The Appel-Jacobson searching algorithm is used to search possible moves. The lexicon with all words is available for this algorithm. It's stored in Directed Acyclic Word Graph (DAWG), which provides fast data searching and data compression too, so the size of the lexicon is comparatively small considering the target platform. The final Java application for celluar phones (MIDP 2.0) adds graphical interface and game control so it provides playing SCRABBLE brand crossword game against artificial intelligence or against human.
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Visualization of Longest Prefix Match Algorithms
Fomiczew, Jiří ; Matoušek, Jiří (referee) ; Kováčik, Michal (advisor)
This thesis describes the design and implementation of program for vizualization of algorithms for longest pre fix match (LPM), which is one of the most important tasks for packet classi cation and routing in TCP/IP networks. It describes necessary theory and details about selected algorithms - Trie, Tree Bitmap and CPE. Furthermore, it describes the design and implementation of program for vizualization of the search process of these algorithms with emphasis on the potential use for educational purposes. Finally, it describes the possibilities for future development and expansion of the program.
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Graphical Demonstration of Selected Route Lookup Algorithm
Ohrádka, Marek ; Kaštil, Jan (referee) ; Puš, Viktor (advisor)
This bachelor's thesis deals with IP routing and different routing protocols. It describes different solutions of the longest prefix matching, advantages and disadvantages of different approaches. Shows the concept of the trie data structure and its alternatives. Describes the Shape Shifting Trie data structure in detail, as well as process of its creation and the way of traversing the nodes in SST route lookup algorithm. At last, application design and implementation is described. Main purpose of the application is to graphically demonstrate the function of SST route lookup algorithm. This thesis shows decomposition approach to this task, describes major problems and its solution.
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