Una mejora en tiempo del trie de sufijos

Un trie de sufijos es un índice para bases de datos de texto que permite resolver eficientemente las operaciones de búsqueda pero que necesita en espacio 10 veces el tamaño del texto indexado. En [14] se propone una nueva representación compacta del trie de sufijos que resulta eficiente en espacio y que permite un posterior paginado del índice. En este artículo presentamos una mejora en tiempo de búsqueda de esta representación compacta del trie de sufijos manteniendo la competitividad en espacio..XVI Workshop Bases de Datos y Minería de Datos.Red de Universidades con Carreras en Informátic

Compressing computer programs

This paper describes a scheme for compressing programs written in a particular programming language—which can be any language that has a formal lexical and syntactic description—in such a way that they can be reproduced exactly. Only syntactically correct programs can be compressed. The scheme is illustrated on the Pascal language, and compression results are given for a corpus of Pascal programs; but it is by no means restricted to Pascal. In fact, we discuss how a "compressor-generator" program can be constructed that creates a compressor automatically from a formal specification of a programming language, in much the same way as a parser generator creates a syntactic parser from a formal language description

Una mejora en tiempo del trie de sufijos

Un trie de sufijos es un índice para bases de datos de texto que permite resolver eficientemente las operaciones de búsqueda pero que necesita en espacio 10 veces el tamaño del texto indexado. En [14] se propone una nueva representación compacta del trie de sufijos que resulta eficiente en espacio y que permite un posterior paginado del índice. En este artículo presentamos una mejora en tiempo de búsqueda de esta representación compacta del trie de sufijos manteniendo la competitividad en espacio..XVI Workshop Bases de Datos y Minería de Datos.Red de Universidades con Carreras en Informátic

Una mejora en tiempo del trie de sufijos

Un trie de sufijos es un índice para bases de datos de texto que permite resolver eficientemente las operaciones de búsqueda pero que necesita en espacio 10 veces el tamaño del texto indexado. En [14] se propone una nueva representación compacta del trie de sufijos que resulta eficiente en espacio y que permite un posterior paginado del índice. En este artículo presentamos una mejora en tiempo de búsqueda de esta representación compacta del trie de sufijos manteniendo la competitividad en espacio..XVI Workshop Bases de Datos y Minería de Datos.Red de Universidades con Carreras en Informátic

Graph-based compression of dynamic 3D point cloud sequences

This paper addresses the problem of compression of 3D point cloud sequences that are characterized by moving 3D positions and color attributes. As temporally successive point cloud frames are similar, motion estimation is key to effective compression of these sequences. It however remains a challenging problem as the point cloud frames have varying numbers of points without explicit correspondence information. We represent the time-varying geometry of these sequences with a set of graphs, and consider 3D positions and color attributes of the points clouds as signals on the vertices of the graphs. We then cast motion estimation as a feature matching problem between successive graphs. The motion is estimated on a sparse set of representative vertices using new spectral graph wavelet descriptors. A dense motion field is eventually interpolated by solving a graph-based regularization problem. The estimated motion is finally used for removing the temporal redundancy in the predictive coding of the 3D positions and the color characteristics of the point cloud sequences. Experimental results demonstrate that our method is able to accurately estimate the motion between consecutive frames. Moreover, motion estimation is shown to bring significant improvement in terms of the overall compression performance of the sequence. To the best of our knowledge, this is the first paper that exploits both the spatial correlation inside each frame (through the graph) and the temporal correlation between the frames (through the motion estimation) to compress the color and the geometry of 3D point cloud sequences in an efficient way

Proceedings of the Third Symposium on Programming Languages and Software Tools : Kääriku, Estonia, August 23-24 1993

http://www.ester.ee/record=b1064507*es

Hardware Accelerators for Animated Ray Tracing

Future graphics processors are likely to incorporate hardware accelerators for real-time ray tracing, in order to render increasingly complex lighting effects in interactive applications. However, ray tracing poses difficulties when drawing scenes with dynamic content, such as animated characters and objects. In dynamic scenes, the spatial datastructures used to accelerate ray tracing are invalidated on each animation frame, and need to be rapidly updated. Tree update is a complex subtask in its own right, and becomes highly expensive in complex scenes. Both ray tracing and tree update are highly memory-intensive tasks, and rendering systems are increasingly bandwidth-limited, so research on accelerator hardware has focused on architectural techniques to optimize away off-chip memory traffic. Dynamic scene support is further complicated by the recent introduction of compressed trees, which use low-precision numbers for storage and computation. Such compression reduces both the arithmetic and memory bandwidth cost of ray tracing, but adds to the complexity of tree update.This thesis proposes methods to cope with dynamic scenes in hardware-accelerated ray tracing, with focus on reducing traffic to external memory. Firstly, a hardware architecture is designed for linear bounding volume hierarchy construction, an algorithm which is a basic building block in most state-of-the-art software tree builders. The algorithm is rearranged into a streaming form which reduces traffic to one-third of software implementations of the same algorithm. Secondly, an algorithm is proposed for compressing bounding volume hierarchies in a streaming manner as they are output from a hardware builder, instead of performing compression as a postprocessing pass. As a result, with the proposed method, compression reduces the overall cost of tree update rather than increasing it. The last main contribution of this thesis is an evaluation of shallow bounding volume hierarchies, common in software ray tracing, for use in hardware pipelines. These are found to be more energy-efficient than binary hierarchies. The results in this thesis both confirm that dynamic scene support may become a bottleneck in real time ray tracing, and add to the state of the art on tree update in terms of energy-efficiency, as well as the complexity of scenes that can be handled in real time on resource-constrained platforms