Browsing by Author "Subramanya, V."
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Item Sigma encoded inverted files(2007) Trotman, A.; Subramanya, V.Compression of term frequency lists and very long document-id lists within an inverted file search engine are examined. Several compression schemes are compared including Elias ? and ? codes, Golomb Encoding, Variable Byte Encoding, and a class of word- based encoding schemes including Simple-9, Relative-10 and Carryover-12. It is shown that these compression methods are not well suited to compressing these kinds of lists of numbers. Of those tested, Carryover-12 is preferred because it is both effective at compression and fast at decompression. A novel technique, Sigma Encoding prior to compression, is proposed and tested. Sigma Encoding utilizes a parameterized dictionary to reduce the number of bits necessary to store an integer. This method shows an about 0.3 bit per integer improvement over Carryover-12 while costing only about 3 extra clock cycles per integer to decompress. Copyright 2007 ACM.Item Sigma encoded inverted files(2007) Trotman, A.; Subramanya, V.Compression of term frequency lists and very long document-id lists within an inverted file search engine are examined. Several compression schemes are compared including Elias γ and δ codes, Golomb Encoding, Variable Byte Encoding, and a class of word- based encoding schemes including Simple-9, Relative-10 and Carryover-12. It is shown that these compression methods are not well suited to compressing these kinds of lists of numbers. Of those tested, Carryover-12 is preferred because it is both effective at compression and fast at decompression. A novel technique, Sigma Encoding prior to compression, is proposed and tested. Sigma Encoding utilizes a parameterized dictionary to reduce the number of bits necessary to store an integer. This method shows an about 0.3 bit per integer improvement over Carryover-12 while costing only about 3 extra clock cycles per integer to decompress. Copyright 2007 ACM.Item Using graph layout to generalise focus+context image magnification and distortion(2012) Martin, S.; Subramanya, V.; Mills, S.We present a novel framework for performing distortion-oriented focus+context image magnification. Our framework uses algorithms from graph drawing to manipulate the mesh underlying an image. Specifically, we apply a spectral graph layout algorithm to a weighted graph, where vertices in the graph correspond to pixels in the image, and edges connect directly adjacent vertices/pixels. By assigning appropriate weights to the edges, we can replicate the results of previous distortion-oriented approaches. In addition, we can perform image-aware distortion by using pixel values to influence the edge weights of our graph. We compare our approach to previous methods and demonstrate new results using image-based edge weighting schemes. � 2012 ACM.Item Using graph layout to generalise focus+context image magnification and distortion(2012) Martin, S.; Subramanya, V.; Mills, S.We present a novel framework for performing distortion-oriented focus+context image magnification. Our framework uses algorithms from graph drawing to manipulate the mesh underlying an image. Specifically, we apply a spectral graph layout algorithm to a weighted graph, where vertices in the graph correspond to pixels in the image, and edges connect directly adjacent vertices/pixels. By assigning appropriate weights to the edges, we can replicate the results of previous distortion-oriented approaches. In addition, we can perform image-aware distortion by using pixel values to influence the edge weights of our graph. We compare our approach to previous methods and demonstrate new results using image-based edge weighting schemes. © 2012 ACM.