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Reinforcement learning for routing in communication networksAndrag, Walter H. 04 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Routing policies for packet-switched communication networks must be able to adapt
to changing traffic patterns and topologies. We study the feasibility of implementing
an adaptive routing policy using the Q-Learning algorithm which learns sequences of
actions from delayed rewards. The Q-Routing algorithm adapts a network's routing
policy based on local information alone and converges toward an optimal solution. We
demonstrate that Q-Routing is a viable alternative to other adaptive routing methods
such as Bellman-Ford. We also study variations of Q-Routing designed to better explore
possible routes and to take into consideration limited buffer size and optimize multiple
objectives. / AFRIKAANSE OPSOMMING:Die roetering in kommunikasienetwerke moet kan aanpas by veranderings in netwerktopologie
en verkeersverspreidings. Ons bestudeer die bruikbaarheid van 'n aanpasbare
roeteringsalgoritme gebaseer op die "Q-Learning"-algoritme wat dit moontlik maak om
'n reeks besluite te kan neem gebaseer op vertraagde vergoedings. Die roeteringsalgoritme
gebruik slegs nabygelee inligting om roeteringsbesluite te maak en konvergeer na
'n optimale oplossing. Ons demonstreer dat die roeteringsalgoritme 'n goeie alternatief
vir aanpasbare roetering is, aangesien dit in baie opsigte beter vaar as die Bellman-Ford
algoritme. Ons bestudeer ook variasies van die roeteringsalgoritme wat beter paaie kan
ontdek, minder geheue gebruik by netwerkelemente, en wat meer as een doelfunksie
kan optimeer.
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The modelling of TCP traffic in MPLS networksVillet, Marcel 04 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The Internet has experienced tremendous growth in the last three decades and has emerged as a
platform to carryall forms of communications including voice, video and data. Along with this
growth came the urgency for quality of service (QoS) controls in IP networks as different types of
traffics have different service requirements. Although the IP protocol is able to scale to very large
networks, it does not provide sufficient functionality for traffic engineering in order to enable QoS
control.
Multi-protocol label switching (MPLS) is a new routing technology that enhances IP with some
QoS concepts from ATM and uses relatively simple packet forwarding mechanisms. MPLS has the
ability to perform traffic engineering and QoS control by routing traffic flowson virtual connections
called label switched paths (LSPs) which are assigned capacity.
A large portion of the traffic carried on the Internet consists of data traffic in the form of TCP
traffic. This thesis investigates several TCP models to find the ones most suitable to represent
TCP traffic in MPLS networks. The models consist of three types. The first type models a single
TCP source and the second type models a fixed number of TCP sources. The third type models
an infinite number of TCP sources. The models were evaluated by comparing their throughput
predictions and results obtained from simulation experiments that were done with the widely-used
simulator ns. We also present a simple derivation of the 1/,;e law for the TCP congestion window
size where e is the packet loss probability. / AFRIKAANSE OPSOMMING:In die afgelope drie dekades het die Internet beduidende groei ervaar, soveel so dat dit ontluik het
as 'n medium om alle tipes van moderne kommunikasies te hanteer insluitend telefoon, video en
data. Hierdie groei het gepaard gegaan met die behoefte na diensvlak (QoS) meganismes in IP
netwerke aangesien verskillende tipe kommunikasies verskillende diens vereistes het. Alhoewel die
IP protokol skalleerbaar is tot baie groot netwerke, voorsien dit nie voldoende funksionaliteit om
QoS beheer toe te pas nie.
"Multi-protocol label switching" (MPLS) is 'n nuwe roeterings tegnologie wat IP aanvul met QoS
konsepte van ATM en dit maak gebruik van relatief eenvoudige pakkie versendings-meganismes.
MPLS het die vermoe om netwerk-verkeer reeling en QoS beheer toe te pas deur verkeers-strome
te roeteer op virtuele roetes genaamd "label switched paths" (LSPs) aan wie kapasiteit toegeken
is.
'n Beduidende gedeelte van Internet-verkeer bestaan uit TCP-verkeer. Hierdie tesis ondersoek
verskillende modelle van TCP om die te vind wat die mees geskik is om TCP verkeer in MPLS
netwerke te verteenwoordig. Drie tipes modelle is ondersoek. Die eerste tipe moduleer 'n enkele
TCP verkeersbron en die tweede tipe moduleer 'n vasgestelde aantal TCP verkeersbronne. Die
derde tipe moduleer 'n oneindige aantal verkeersbronne. Die modelle is geevalueer deur hul voorspellings
van die tempo van data transmissie te vergelyk met resultate van simulasies. Die simulasies
is gedoen met die veelgebruikte simulator ns. Hierdie tesis bevat ook 'n eenvoudige afleiding
vir die 1/,;e wet vir die TCP oorlading venster grootte met e die verlies waarskeinlikheid van 'n
netwerk pakkie.
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FATKID : a Finite Automaton ToolkitHuysamen, Nico 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: This thesis presents the FATKID Finite Automata Toolkit. While a lot
of toolkits currently exist which can manipulate and process nite state
automata, this toolkit was designed to e ectively and e ciently generate,
manipulate and process large numbers of nite automata by distributing
the work
ow across machines and running the computations in parallel.
Other toolkits do not currently provide this functionality. We show that
this framework is user-friendly and extremely extensible. Furthermore we
show that the system e ectively distributes the work to reduce computation
time. / AFRIKAANSE OPSOMMING: In hierdie tesis bespreek ons die FATKID Eindige Automaat Toestel. Al-
hoewel daar reeds toestelle bestaan wat automate kan genereer, manupileer,
en bewerkings daarmee kan uitvoer, is daar egter geen toestelle wat dit op
die skaal kan doen wat ons vereis deur die proses te versprei na 'n aantal
nodes nie. Ons vereis 'n stelsel wat mew baie groot aantalle automate werk.
Die stelsel moet dan die gewensde prosesse in 'n verspreide omgewing, en in
parallel uitvoer om verwerkingstyd te verminder. Ons sal wys dat ons stelsel
nie net hierdie doel bereik nie, maar ook dat dit gebruikers-vriendelik is en
maklik om uit te brei.
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Bug-finding and test case generation for java programs by symbolic executionBester, Willem Hendrik Karel 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this dissertation we present a software tool, Artemis, that symbolically executes Java virtual
machine bytecode to find bugs and automatically generate test cases to trigger the bugs found. Symbolic execution is a technique of static software analysis that entails analysing code over symbolic inputs—essentially, classes of inputs—where each class is formulated as constraints over some input domain. The analysis then proceeds in a path-sensitive way adding the constraints resulting from a symbolic choice at a program branch to a path condition, and branching non-deterministically over the path condition. When a possible error state is reached, the path condition can be solved, and if soluble, value assignments retrieved to be used to generate explicit test cases in a unit testing framework. This last step enhances confidence that bugs are real, because testing is forced through normal language semantics, which could prevent certain states from being reached.
We illustrate and evaluate Artemis on a number of examples with known errors, as well as on a large, complex code base. A preliminary version of this work was successfully presented
at the SAICSIT conference held on 1–3 October 2012, in Centurion, South Africa. / AFRIKAANSE OPSOMMING: In die dissertasie bied ons ’n stuk sagtewaregereedskap, Artemis, aan wat biskode van die Java
virtuele masjien simbolies uitvoer om foute op te spoor en toetsgevalle outomaties voort te bring om die foute te ontketen. Simboliese uitvoering is ’n tegniek van statiese sagteware-analise wat behels dat kode oor simboliese toevoere—in wese, klasse van toevoer—geanaliseer word, waar elke klas geformuleer word as beperkinge oor ’n domein. Die analise volg dan ’n pad-sensitiewe benadering deur die domeinbeperkinge, wat volg uit ’n simboliese keuse by ’n programvertakking, tot ’n padvoorwaarde by te voeg en dan nie-deterministies vertakkings oor die padvoorwaarde te volg. Wanneer ’n moontlike fouttoestand bereik word, kan die padvoorwaarde opgelos word, en indien dit oplaasbaar is, kan waardetoekennings verkry word om eksplisiete toetsgevalle in ’n eenheidstoetsingsraamwerk te formuleer. Die laaste stap verhoog vertroue dat die foute gevind werklik is, want toetsing word deur die normale semantiek van die taal geforseer, wat sekere toestande onbereikbaar maak.
Ons illustreer en evalueer Artemis met ’n aantal voorbeelde waar die foute bekend is, asook op ’n groot, komplekse versameling kode. ’n Voorlopige weergawe van die´ werk is suksesvol by die SAICSIT-konferensie, wat van 1 tot 3 Oktober 2012 in Centurion, Suid-Afrika,
gehou is, aangebied.
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Criteria for the evaluation of private cloud computingTheron, Piet 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Cloud computing is seen as one of top 10 disruptive changes in IT for the
next decade by leading research analysts. Consequently, enterprises are
starting to investigate the effect it will have on the strategic direction of their
businesses and technology stacks. Because of the disruptive nature of the
paradigm shift introduced by it, as well as the strategic impact thereof, it is
necessary that a structured approach with regard to risk, value and operational
cost is followed with the decision on its relevance, as well as the selection of a
platform if needed.
The purpose of this thesis is to provide a reference model and its associating
framework that can be used to evaluate private cloud management platforms,
as well as the technologies associated with it. / AFRIKAANSE OPSOMMING: Wolk berekening word deur vooraanstaande navorsing ontleders as een
van die top 10 ontwrigtende veranderings vir IT in die volgende dekade beskou. Gevolglik begin korporatiewe ondernemings met ondersoeke om te
bepaal wat die invloed daarvan op hulle strategiese rigting en tegnologië gaan
wees. Die ontwrigtende aard van die paradigma skuif, asook die strategiese
impak daarvan, noodsaak ’n gestruktureerde ondersoek na die toepaslikheid
en keuse van ’n platform, indien nodig, met betrekking tot risiko, waarde en
operasionele koste.
Die doel van hierdie tesis is om ’n verwysings model, en ’n raamwerk wat
dit implementeer, saam te stel wat dan gebruik kan word om privaat wolk
berekening platforms te evalueer.
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A model checker for the LF systemGerber, Erick D. B. 03 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Computer aided veri cation techniques, such as model checking, can be used to improve the
reliability of software. Model checking is an algorithmic approach to illustrate the correctness
of temporal logic speci cations in the formal description of hardware and software systems.
In contrast to traditional testing tools, model checking relies on an exhaustive search of all
the possible con gurations that these systems may exhibit. Traditionally model checking is
applied to abstract or high level designs of software. However, often interpreting or translating
these abstract designs to implementations introduce subtle errors. In recent years one
trend in model checking has been to apply the model checking algorithm directly to the
implementations instead.
This thesis is concerned with building an e cient model checker for a small concurrent langauge
developed at the University of Stellenbosch. This special purpose langauge, LF, is
aimed at developement of small embedded systems. The design of the language was carefully
considered to promote safe programming practices. Furthermore, the language and its runtime
support system was designed to allow directly model checking LF programs. To achieve
this, the model checker extends the existing runtime support infrastructure to generate the
state space of an executing LF program. / AFRIKAANSE OPSOMMING: Rekenaar gebaseerde program toetsing, soos modeltoetsing, kan gebruik word om die betroubaarheid
van sagteware te verbeter. Model toetsing is 'n algoritmiese benadering om
die korrektheid van temporale logika spesi kasies in die beskrywing van harde- of sagteware
te bewys. Anders as met tradisionlee program toetsing, benodig modeltoetsing 'n volledige
ondersoek van al die moontlike toestande waarin so 'n beskrywing homself kan bevind. Model
toetsing word meestal op abstrakte modelle van sagteware of die ontwerp toegepas. Indien
die ontwerp of model aan al die spesi kasies voldoen word die abstrakte model gewoontlik
vertaal na 'n implementasie. Die vertalings proses word gewoontlik met die hand gedoen
en laat ruimte om nuwe foute, en selfs foute wat uitgeskakel in die model of ontwerp is te
veroorsaak. Deesdae, is 'n gewilde benadering tot modeltoetsing om di e tegnieke direk op die
implementasie toe te pas, en sodoende die ekstra moeite van model konstruksie en vertaling
uit te skakel.
Hierdie tesis handel oor die ontwerp, implementasie en toetsing van 'n e ektiewe modeltoetser
vir 'n klein gelyklopende taal, LF, wat by die Universiteit van Stellenbosch ontwikkel is. Die
enkeldoelige taal, LF, is gemik op die veilige ontwikkeling van ingebedde sagteware. Die
taal is ontwerp om veilige programmerings praktyke aan te moedig. Verder is die taal en
die onderliggende bedryfstelsel so ontwerp om 'n model toetser te akkomodeer. Om die LF
programme direk te kan toets, is die model toetser 'n integrale deel van die bedryfstelsel sodat
dit die program kan aandryf om alle moontlike toestande te besoek.
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Improved models of biological sequence evolutionMurrel, Benjamin 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Computational molecular evolution is a field that attempts to characterize
how genetic sequences evolve over phylogenetic trees – the branching processes
that describe the patterns of genetic inheritance in living organisms. It has a
long history of developing progressively more sophisticated stochastic models
of evolution. Through a probabilist’s lens, this can be seen as a search for
more appropriate ways to parameterize discrete state continuous time Markov
chains to better encode biological reality, matching the historical processes
that created empirical data sets, and creating useful tools that allow biologists
to test specific hypotheses about the evolution of the organisms or the genes
that interest them. This dissertation is an attempt to fill some of the gaps that
persist in the literature, solving what we see as existing open problems. The
overarching theme of this work is how to better model variation in the action
of natural selection at multiple levels: across genes, between sites, and over
time. Through four published journal articles and a fifth in preparation, we
present amino acid and codon models that improve upon existing approaches,
providing better descriptions of the process of natural selection and better
tools to detect adaptive evolution. / AFRIKAANSE OPSOMMING: Komputasionele molekulêre evolusie is ’n navorsingsarea wat poog om die evolusie
van genetiese sekwensies oor filogenetiese bome – die vertakkende prosesse
wat die patrone van genetiese oorerwing in lewende organismes beskryf – te karakteriseer.
Dit het ’n lang geskiedenis waartydens al hoe meer gesofistikeerde
waarskynlikheidsmodelle van evolusie ontwikkel is. Deur die lens van waarskynlikheidsleer
kan hierdie proses gesien word as ’n soektog na meer gepasde
metodes om diskrete-toestand kontinuë-tyd Markov kettings te parametriseer
ten einde biologiese realiteit beter te enkodeer – op so ’n manier dat die historiese
prosesse wat tot die vorming van biologiese sekwensies gelei het nageboots
word, en dat nuttige metodes geskep word wat bioloë toelaat om spesifieke hipotesisse
met betrekking tot die evolusie van belanghebbende organismes of
gene te toets. Hierdie proefskrif is ’n poging om sommige van die gapings
wat in die literatuur bestaan in te vul en bestaande oop probleme op te los.
Die oorkoepelende tema is verbeterde modellering van variasie in die werking
van natuurlike seleksie op verskeie vlakke: variasie van geen tot geen, variasie
tussen posisies in gene en variasie oor tyd. Deur middel van vier gepubliseerde
joernaalartikels en ’n vyfde artikel in voorbereiding, bied ons aminosuur- en
kodon-modelle aan wat verbeter op bestaande benaderings – hierdie modelle
verskaf beter beskrywings van die proses van natuurlike seleksie sowel as beter
metodes om gevalle van aanpassing in evolusie te vind.
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Relieving the cognitive load of constructing molecular biological ontology based queries by means of visual aids.O'Neill, Kieran. January 2007 (has links)
The domain of molecular biology is complex and vast. Bio-ontologies and information visualisation have arisen in recent years as means to assist biologists in making sense of this information. Ontologies can enable the construction of conceptual queries, but existing systems to do this are too technical for most biologists. OntoDas, the software developed as part of this thesis work, demonstrates how the application of techniques from information visualisation and human computer interaction can result in software which enables biologists to construct conceptual queries. / Thesis (M.Comp.Sc.)-Universty of KwaZulu-Natal, Pietermaritzburg, 2007.
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Gabor filter parameter optimization for multi-textured images : a case study on water body extraction from satellite imagery.Pillay, Maldean. January 2012 (has links)
The analysis and identification of texture is a key area in image processing and computer
vision. One of the most prominent texture analysis algorithms is the Gabor Filter.
These filters are used by convolving an image with a family of self similar filters or
wavelets through the selection of a suitable number of scales and orientations, which
are responsible for aiding in the identification of textures of differing coarseness and
directions respectively.
While extensively used in a variety of applications, including, biometrics such as iris and
facial recognition, their effectiveness depend largely on the manual selection of different
parameters values, i.e. the centre frequency, the number of scales and orientations, and
the standard deviations. Previous studies have been conducted on how to determine
optimal values. However the results are sometimes inconsistent and even contradictory.
Furthermore, the selection of the mask size and tile size used in the convolution process
has received little attention, presumably since they are image set dependent.
This research attempts to verify specific claims made in previous studies about the
influence of the number of scales and orientations, but also to investigate the variation of
the filter mask size and tile size for water body extraction from satellite imagery. Optical
satellite imagery may contain texture samples that are conceptually the same (belong
to the same class), but are structurally different or differ due to changes in illumination,
i.e. a texture may appear completely different when the intensity or position of a light
source changes.
A systematic testing of the effects of varying the parameter values on optical satellite
imagery is conducted. Experiments are designed to verify claims made about the influence of varying the scales and orientations within predetermined ranges, but also to
show the considerable changes in classification accuracy when varying the filter mask
and tile size. Heuristic techniques such as Genetic Algorithms (GA) can be used to find
optimum solutions in application domains where an enumeration approach is not feasible.
Hence, the effectiveness of a GA to automate the process of determining optimum
Gabor filter parameter values for a given image dataset is also investigated.
The results of the research can be used to facilitate the selection of Gabor filter parameters
for applications that involve multi-textured image segmentation or classification,
and specifically to guide the selection of appropriate filter mask and tile sizes for automated
analysis of satellite imagery. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2012.
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On the performance of recent swarm based metaheuristics for the traveling tournament problem.Saul, Sandile Sinethemba . 08 October 2014 (has links)
M.Sc. University of KwaZulu-Natal, Durban 2013.
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