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Item Open Access Adaptation of multiway-merge sorting algorithm to MIMD architectures with an experimental study(2002) Cantürk, LeventSorting is perhaps one of the most widely studied problems of computing. Numerous asymptotically optimal sequential algorithms have been discovered. Asymptotically optimal algorithms have been presented for varying parallel models as well. Parallel sorting algorithms have already been proposed for a variety of multiple instruction, multiple data streams (MIMD) architectures. In this thesis, we adapt the multiwaymerge sorting algorithm that is originally designed for product networks, to MIMD architectures. It has good load balancing properties, modest communication needs and well performance. The multiway-merge sort algorithm requires only two all-to-all personalized communication (AAPC) and two one-to-one communications independent from the input size. In addition to evenly distributed load balancing, the algorithm requires only size of 2N/P local memory for each processor in the worst case, where N is the number of items to be sorted and P is the number of processors. We have implemented the algorithm on the PC Cluster that is established at Computer Engineering Department of Bilkent University. To compare the results we have implemented a sample sort algorithm (PSRS Parallel Sorting by Regular Sampling) by X. Liu et all and a parallel quicksort algorithm (HyperQuickSort) on the same cluster. In the experimental studies we have used three different benchmarks namely Uniformly, Gaussian, and Zero distributed inputs. Although the multiwaymerge algorithm did not achieve better results than the other two, which are theoretically cost optimal algorithms, there are some cases that the multiway-merge algorithm outperforms the other two like in Zero distributed input. The results of the experiments are reported in detail. The multiway-merge sort algorithm is not necessarily the best parallel sorting algorithm, but it is expected to achieve acceptable performance on a wide spectrum of MIMD architectures.Item Open Access Approaches for inequity-averse sorting(Elsevier, 2016) Karsu, Ö.In this paper we consider multi-criteria sorting problems where the decision maker (DM) has equity concerns. In such problems each alternative represents an allocation of an outcome (e.g. income, service level, health outputs) over multiple indistinguishable entities. We propose three sorting algorithms that are different from the ones in the current literature in the sense that they apply to cases where the DM's preference relation satisfies anonymity and convexity properties. The first two algorithms are based on additive utility function assumption and the third one is based on the symmetric Choquet integral concept. We illustrate their use by sorting countries into groups based on their income distributions using real-life data. To the best of our knowledge our work is the first attempt to solve sorting problems in a symmetric setting.Item Open Access Balanced parallel sort on hypercube multiprocessors(IEEE, 1993) Abali, B.; Özgüner, F.; Bataineh, A.A parallel sorting algorithm for sorting n elements evenly distributed over Zd = p nodes of a d-dimensional hypercube is presented. The average running time of the algorithm is O( (n log n)/p + p log2 n). The algorithm maintains a perfect load balance in the nodes by determining the (kn/p)th elements (k = 1,. . . , (p - 1)) of the final sorted list in advance. These p - 1 keys are used to partition the sorted sublists in each node to redistribute data to the nodes to be merged in parallel. The nodes finish the sort with an equal number of elements (n/p) regardless of the data distribution. A parallel selection algorithm for determining the balanced partition keys in O(p log2 n) time is presented. The speed of the sorting algorithm is further enhanced by the distanced communication capability of the iPSC/2 hypercube computer and a novel conflict-free routing algorithm. Experimental results on a 16-node hypercube computer show that the new sorting algorithm is competitive with the previous algorithms, and faster for skewed data distributions.Item Open Access Feasibility of impact-acoustic emissions for detection of damaged wheat kernels(Elsevier BV, 2007-05) Pearson, T.; Çetin, A. Enis; Tewfik, A. H.; Haff, R. P.A non-destructive, real time device was developed to detect insect damage, sprout damage, and scab damage in kernels of wheat. Kernels are impacted onto a steel plate and the resulting acoustic signal analyzed to detect damage. The acoustic signal was processed using four different methods: modeling of the signal in the time-domain, computing time-domain signal variances and maximums in short-time windows, analysis of the frequency spectrum magnitudes, and analysis of a derivative spectrum. Features were used as inputs to a stepwise discriminant analysis routine, which selected a small subset of features for accurate classification using a neural network. For a network presented with only insect damaged kernels (IDK) with exit holes and undamaged kernels, 87% of the former and 98% of the latter were correctly classified. It was also possible to distinguish undamaged, IDK, sprout-damaged, and scab-damaged kernels.Item Open Access Image-space decomposition algorithms for sort-first parallel volume rendering of unstructured grids(Springer, 2000) Kutluca, H.; Kurç, T. M.; Aykanat, CevdetTwelve adaptive image-space decomposition algorithms are presented for sort-first parallel direct volume rendering (DVR) of unstructured grids on distributed-memory architectures. The algorithms are presented under a novel taxonomy based on the dimension of the screen decomposition, the dimension of the workload arrays used in the decomposition, and the scheme used for workload-array creation and querying the workload of a region. For the 2D decomposition schemes using 2D workload arrays, a novel scheme is proposed to query the exact number of screen-space bounding boxes of the primitives in a screen region in constant time. A probe-based chains-on-chains partitioning algorithm is exploited for load balancing in optimal 1D decomposition and iterative 2D rectilinear decomposition (RD). A new probe-based optimal 2D jagged decomposition (OJD) is proposed which is much faster than the dynamic-programming based OJD scheme proposed in the literature. The summed-area table is successfully exploited to query the workload of a rectangular region in constant time in both OJD and RD schemes for the subdivision of general 2D workload arrays. Two orthogonal recursive bisection (ORB) variants are adapted to relax the straight-line division restriction in conventional ORB through using the medians-of-medians approach on regular mesh and quadtree superimposed on the screen. Two approaches based on the Hilbert space-filling curve and graph-partitioning are also proposed. An efficient primitive classification scheme is proposed for redistribution in 1D, and 2D rectilinear and jagged decompositions. The performance comparison of the decomposition algorithms is modeled by establishing appropriate quality measures for load-balancing, amount of primitive replication and parallel execution time. The experimental results on a Parsytec CC system using a set of benchmark volumetric datasets verify the validity of the proposed performance models. The performance evaluation of the decomposition algorithms is also carried out through the sort-first parallelization of an efficient DVR algorithm.Item Open Access The latest arrival hub location problem(Institute for Operations Research and the Management Sciences (INFORM), 2001) Kara, B. Y.; Tansel, B. Ç.The traditionally studied hub location problems in the literature pay attention to flight times but not to transient times spent at hubs for unloading, loading, and sorting operations. The transient times may constitute a significant portion of the total delivery time for cargo delivery systems. We focus on the minimization of the arrival time of the last arrived item in cargo delivery systems and develop a model that correctly computes the arrival times by taking into account both the flight times and the transient times. Nonlinear and linear integer formulations are given and computational results are provided. The effects of delays on the system performance are analyzed.Item Open Access A tool for pattern information extraction and defect quantification from crystal structures(Elsevier, 2015) Okuyan, E.; Okuyan, E.In this paper, we present a revised version of BilKristal 2.0 tool. We added defect quantification functionality to assess crystalline defects. We improved visualization capabilities by adding transparency support and runtime visibility sorting. Discovered bugs are fixed and small performance optimizations are made. New version program summary Program title: BilKristal 3.0 Catalogue identifier: ADYU-v3-0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADYU-v3-0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 1868 923 No. of bytes in distributed program, including test data, etc.: 8854 507 Distribution format: tar.gz Programming language: C, C++, Microsoft.NET Framework 2.0 and OpenGL Libraries. Computer: Personal Computers with Windows operating system. Operating system: Windows XP or higher. RAM: 20-60 Megabytes. Classification: 8. Catalogue identifier of previous version: ADYU-v2-0 Journal reference of previous version: Comput. Phys. Comm. 185 (2014) 442 External routines: Microsoft.NET Framework 2.0. For the visualization tool, graphics card driver should also support OpenGL. Does the new version supersede the previous version?: Yes Nature of problem: Determining the crystal structure parameters of a material is a very important issue in crystallography. Knowing the crystal structure parameters helps the understanding of the physical behavior of material. For complex structures, particularly for materials which also contain local symmetry as well as global symmetry, obtaining crystal parameters can be very hard. Solution method: The tool extracts crystal parameters such as primitive vectors, basis vectors and identifies the space group from atomic coordinates of crystal structures. Reasons for new version: Additional features, Compatibility issues with newer development environments, Performance optimizations, Minor bug corrections. Summary of revisions:Defect quantification capability is added. The tool can process the imperfect crystal structures, finds and quantifies the crystalline defects. The tool is capable of finding positional defects, vacancy defects, substitutional impurities and interstitial impurities. The algorithms presented in [3] are used for defect quantification implementation.Transparency support is added to the visualization tool. Users are now allowed to set the transparency of each atom type individually.Runtime visibility sorting functionality is added to facilitate correct transparency computations.Visual Studio 2012 support is added. Visual Studio 2012 specific project files are created and the project is tested with this development environment.In visualization tool, an unused log file was created. This issue is corrected.In visualization tool, some OpenGL calls which are executed at every draw are changed to be executed only when they are needed, improving the visualization performance.Restrictions: Assumptions are explained in [1,2]. However, none of them can be considered as a restriction onto the complexity of the problem. Running time: The tool was able to process input files with more than a million atoms in less than 20 s on a PC with an Athlon quad-core CPU at 3.2 GHz using the default parameter values. References: [1] Erhan Okuyan, Ugur Güdükbay, Oguz Gülseren, Pattern information extraction from crystal structures, Comput. Phys. Comm. 176 (2007) 486. [2] Erhan Okuyan, Ugur Güdükbay, BilKristal 2.0: A tool for pattern information extraction from crystal structures, Comput. Phys. Comm. 185 (2014) 442. [3] Erhan Okuyan, Ugur Güdükbay, Ceyhun Bulutay, Karl-Heinz Heinig, MaterialVis: material visualization tool using direct volume and surface rendering techniques, J. Mol. Graphics Model. 50201450-60. © 2014 The Authors.