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2 2019

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Efficient astronomical data condensation using approximate nearest neighbors

Łukasik Szymon, Lalik Konrad, Sarna Piotr, Kowalski Piotr A., Charytanowicz Małgorzata, Kulczycki Piotr

International Journal of Applied Mathematics and Computer Science

2019

Vol. 29, no. 3

467--476

Extracting useful information from astronomical observations represents one of the most challenging tasks of data exploration. This is largely due to the volume of the data acquired using advanced observational tools. While other challenges typical for the class of big data problems (like data variety) are also present, the size of datasets represents the most significant obstacle in visualization and subsequent analysis. This paper studies an efficient data condensation algorithm aimed at providing its compact representation. It is based on fast nearest neighbor calculation using tree structures and parallel processing. In addition to that, the possibility of using approximate identification of neighbors, to even further improve the algorithm time performance, is also evaluated. The properties of the proposed approach, both in terms of performance and condensation quality, are experimentally assessed on astronomical datasets related to the GAIA mission. It is concluded that the introduced technique might serve as a scalable method of alleviating the problem of the dataset size.

Tree-based control space structures for discrete metric sources in 3D meshing

Głut Barbara, Jurczyk Tomasz

Computer Science

2019

Vol. 20 (4)

493--509

This article compares the different variations of the octree and kd-tree structures used to create a control space based on a set of discrete metric point-sources. The control space thus created supervises the generation of the mesh providing efficient access to the required information on the desired shape and size of the mesh elements at each point of the discretized domain. Structures are compared in terms of computational and memory complexity as well as regarding the accuracy of the approximation of the set of discrete metric sources in the created control space structure.