Browsing by Subject "Image-space parallel volume rendering"
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Item Open Access Fast optimal load balancing algorithms for 1D partitioning(Academic Press, 2004) Pınar, A.; Aykanat, CevdetThe one-dimensional decomposition of nonuniform workload arrays with optimal load balancing is investigated. The problem has been studied in the literature as the "chains-on-chains partitioning" problem. Despite the rich literature on exact algorithms, heuristics are still used in parallel computing community with the "hope" of good decompositions and the "myth" of exact algorithms being hard to implement and not runtime efficient. We show that exact algorithms yield significant improvements in load balance over heuristics with negligible overhead. Detailed pseudocodes of the proposed algorithms are provided for reproducibility. We start with a literature review and propose improvements and efficient implementation tips for these algorithms. We also introduce novel algorithms that are asymptotically and runtime efficient. Our experiments on sparse matrix and direct volume rendering datasets verify that balance can be significantly improved by using exact algorithms. The proposed exact algorithms are 100 times faster than a single sparse-matrix vector multiplication for 64-way decompositions on the average. We conclude that exact algorithms with proposed efficient implementations can effectively replace heuristics. © 2004 Elsevier Inc. All rights reserved.Item Open Access Image-space decomposition algorithms for sort-first parallel volume rendering of unstructured grids(1997) Kutluca, HüseyinIn this thesis, image-space decomposition algorithms are proposed and utilized for parallel implementation of a direct volume rendering algorithm. Screen space bounding box of a primitive is used to approximate the coverage of the primitive on the screen. Number of bounding boxes in a region is used as a workload of the region. Exact model is proposed as a new workload array scheme to find exact number of bounding boxes in a rectangular region in O(1) time. Chains-on-chains partitioning algorithms are exploited for load balancing in some of the proposed decomposition schemes. Summed area table scheme is utilized to achieve more efficient optimal jagged decomposition and iterative rectilinear decomposition algorithms. These two 2D decomposition algorithms are utilized for image-space decomposition using the exact model. Also, new algorithms that use inverse area heuristic are implemented for image-space decomposition. Orthogonal recursive bisection algorithm with medians of medians scheme is applied on regular mesh and quadtree superimposed on the screen. Hilbert space filling curve is also exploited for image-space decomposition. 12 image-space decomposition algorithms are experimentally evaluated on a common framework with respect to the load balance performance, the number of shared primitives, and execution time of the decomposition algorithms.