Search results for "Algoritmi"
showing 10 items of 204 documents
Multilayer perceptron training with multiobjective memetic optimization
2016
Machine learning tasks usually come with several mutually conflicting objectives. One example is the simplicity of the learning device contrasted with the accuracy of its performance after learning. Another common example is the trade-off that must often be made between the rate of false positive and false negative predictions in diagnostic applications. For computer programs that learn from data, these objectives are formulated as mathematical functions, each of which describes one facet of the desired learning outcome. Even functions that intend to optimize the same facet may behave in a subtly different and mutually conflicting way, depending on the task and the dataset being examined. Mul…
Kvantu vaicājumu sarežģītība bezkonteksta gramatikām
2019
Bezkonteksta gramatikas un to ģenerētās valodas ir plaši pētīta tēma datorzinātnē. Tām ir dažādi praktiski pielietojumi, piemēram, XML valodā. Savukārt kvantu skaitļošana, it sevišķi kvantu vaicājumu algoritmi, ir datorzinātnes nozare, kas par spīti popularitātei, ir vēl neizpētīta un neskaidra. Šī darba mērķis ir aplūkot vārda piederības problēmu bezkonteksta valodai no kvantu vaicājumu algoritmu puses. Konkrētāk - darbā tika izvirzīti divi uzdevumi. Pirmais uzdevums bija atrast bezkonteksta valodu ar kvantu vaicājumu sarežģītību O(N^c), kur c0 vai pierādīt par tādas neesamību. Otrais uzdevums - uzrādīt intuitīvi saprotamu bezkonteksta valodas konstrukciju, kas ļauj konstruēt valodu ar kva…
Toolbox for Distance Estimation and Cluster Validation on Data With Missing Values
2022
Missing data are unavoidable in the real-world application of unsupervised machine learning, and their nonoptimal processing may decrease the quality of data-driven models. Imputation is a common remedy for missing values, but directly estimating expected distances have also emerged. Because treatment of missing values is rarely considered in clustering related tasks and distance metrics have a central role both in clustering and cluster validation, we developed a new toolbox that provides a wide range of algorithms for data preprocessing, distance estimation, clustering, and cluster validation in the presence of missing values. All these are core elements in any comprehensive cluster analy…
World as Numbers : Living in an Algorithmic Culture
2016
There is a long tradition of trying to grasp the world around us in mathematical terms. From early man perceiving the motion of celestial bodies, to Pythagoras’ ‘celestial harmony’ and to Kepler’s and Newton’s laws of motion, calculations have provided ways to reduce the messy world of instances to a handful of mathematical formulae. Einstein’s Relativity Theory, and even more the quantum physics, complicated the situation, but still, even with random elements involved, the statistics could provide a model to understand the processes of the universe. When calculations grew ever more complex, and computers became necessary tools to deal with them, this lead to the idea of seeing the whole of…
Shape sensitivity analysis for numerical solution of free boundary problems
2005
Kari Kärkkäinen tutki tehokkaita ja käyttökelpoisia ratkaisumenetelmiä vapaita pintoja sisältäville malleille. Hän tarkastelee väitöksessään numeerisessa simuloinnissa käytettävien vapaan pinnan ratkaisumenetelmien tehokkuutta ja niiden parantamista käyttäen matemaattista lähestymistapaa. Kärkkäinen ehdottaa ratkaisumenetelmää, jonka avulla vapaan pinnan tehtävien ratkaiseminen on helpompaa. Menetelmää voi myös soveltaa erilaisiin tilanteisiin. This work is devoted to the development of efficient and robust solution algorithms for a class of free boundary problems. This consists of mathematical analysis of different model problems and the description of numerical implementation to generic f…
Is 're-calibration' of standard cardiovascular disease (CVD) risk algorithms the panacea to improved CVD risk prediction and prevention?
2018
This editorial refers to ‘Equalization of four cardiovascular risk algorithms after systematic recalibration: individual-participant meta-analysis of 86 prospective studies’, by L. Pennells et al., doi:10.1093/eurheartj/ehy653.
Parallel global optimization : structuring populations in differential evolution
2010
On automatic algorithm configuration of vehicle routing problem solvers
2019
Many of the algorithms for solving vehicle routing problems expose parameters that strongly influence the quality of obtained solutions and the performance of the algorithm. Finding good values for these parameters is a tedious task that requires experimentation and experience. Therefore, methods that automate the process of algorithm configuration have received growing attention. In this paper, we present a comprehensive study to critically evaluate and compare the capabilities and suitability of seven state-of-the-art methods in configuring vehicle routing metaheuristics. The configuration target is the solution quality of eight metaheuristics solving two vehicle routing problem variants.…
Rēķināšanas sarežģītības samazināšana ar nejaušību lietošanu
2016
Maģistra darbs „Rēķināšanas sarežģītības samazināšana ar nejaušības lietošanu” iekļauj pētījumu par varbūtisko pieeju rēķināšanas sarežģītības samazināšanai un apskata divus uzdevumus, proti, mulitilneāru polinomu ģenerēšanu un dārza šļūteņu modeļa izveidi, kuriem autore ir veikusi esošo risinājumu izpēti un izstrādājusi savus risinājumu algoritmus. Multilineāru polinomu ģenerēšanas problēmai, kurā tiek ģenerēti polinomi, kura atbilstu Būla funkcijai, ir veikta multilineāro polinomu izpēte, lai noteiktu to īpašības, kuras tiek izmantotas autores izstrādātajā polinomu ģenerēšanas varbūtiskajā algoritmā. Dārza šļūteņu (Garden - Hose) modeļa problēmai, kura ir salīdzinoši jauna (2013. gadā def…