Issues related to the efficient embedding of interprocessor communications required by parallel implementations of intermediate-level vision tasks are discussed. the performance of alternative embeddings of the interp...
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Issues related to the efficient embedding of interprocessor communications required by parallel implementations of intermediate-level vision tasks are discussed. the performance of alternative embeddings of the interprocessor communications required by specific tasks at the intermediate level of vision has been analyzed, and quantitative results have been obtained and compared to the results of corresponding implementations on the Connection Machine. In the quantitative analysis, the cost of communication primitives supported by this machine, characteristics of the task, and parameters which are characteristic of image content are taken into account. Based on the result of this analysis, a methodology is suggested for selecting the most efficient implementation of interprocessor communications among different alternatives.< >
A segmented pipeline architecture for multiresolution, focal, array processing is presented. A buffer is introduced at each point in a pipeline computation at which changes in sample density or analysis area may take ...
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A segmented pipeline architecture for multiresolution, focal, array processing is presented. A buffer is introduced at each point in a pipeline computation at which changes in sample density or analysis area may take place. these buffers divide the pipeline into segments, each with constant data load. When active, a segment runs at its full design rate. Efficiency is maintained by switching processing elements between segments as image data flows through the system. the segmented pipeline architecture is illustrated with an application to image motion analysis.< >
An integrated vision triarchitecture, Vista, for a general-purpose computervision system is described. Vista consists of three parallel architectures. A fine-grained mesh-connected single-instruction multiple-data (S...
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An integrated vision triarchitecture, Vista, for a general-purpose computervision system is described. Vista consists of three parallel architectures. A fine-grained mesh-connected single-instruction multiple-data (SIMD) architecture is proposed to minimize the communication overhead between processing elements in existing mesh-connected architectures. A medium-grained multiple-instruction multiple-data (MIMD) architecture is proposed to alleviate the communication overhead in loosely coupled multiprocessors and the memory contention in tightly coupled multiprocessors. A coarse-grained MIMD architecture is proposed to reduce the communication and input/output (I/O) overheads in existing hypercube multiprocessors. these architectures are exploited for low-, intermediate-, and high-level computervision, respectively. Each architecture shows a performance improvement in each class. the three architectures are pipelined into Vista for a general-purpose computervision system.< >
Regularization has become an important tool for solving many ill-posed problems in approximation theory-for example, in computervision-including surface reconstruction, optical flow, and shape from shading. the autho...
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Regularization has become an important tool for solving many ill-posed problems in approximation theory-for example, in computervision-including surface reconstruction, optical flow, and shape from shading. the authors attempt to determine whether the approach taken in regularization is always the correct one, and to what extent the results of regularization are reliable. they consider as an example a case in which regularization has been used to reconstruct a surface from sparse data, and attempt to determine how strongly the height of the surface at a certain point can be relied upon. these questions are answered by defining a probability distribution on the class of surfaces considered, and computing its expectation and variance. the variance can be used, for instance, to construct a safety strip around the interpolated surface that should not be entered if collision withthe surface is to be avoided.< >
the recovery of depth from defocused images is formulated as a 3-D image restoration problem. A defocused image is modeled as the combinatorial outcome of the depths and intensities of the volume elements (voxels) of ...
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the recovery of depth from defocused images is formulated as a 3-D image restoration problem. A defocused image is modeled as the combinatorial outcome of the depths and intensities of the volume elements (voxels) of an opaque 3-D object. A large depth-of-field image is used to constrain the intensities of the voxels. the depths of voxels are estimated from a highly defocused image by using simulated annealing to solve a constrained optimization problem. It is concluded that the method provides a framework for high-resolution depth recovery from defocused images. the method is computationally-intensive; however, it is amenable to parallel processing and is well suited for small field-of-interest applications.< >
the authors present a highly robust estimator called an MF-estimator for general regression. It is argued that the kind of estimators needed by computervision must be highly robust and that the classical robust estim...
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the authors present a highly robust estimator called an MF-estimator for general regression. It is argued that the kind of estimators needed by computervision must be highly robust and that the classical robust estimators do not render a high robustness. It is explained that the high robustness becomes possible only through partially but completely modeling the unknown log likelihood function. Partial modeling explores a number of important heuristics implicit in the regression problem and takes place by taking them into consideration withthe Bayes statistical decision rule, while maximizing the log likelihood function. Experiments withthe simplest location estimation showed that the performance of the MF-estimator was superior to that of the classical M-estimator.< >
VIKNET (visual knowledge network), an extension of associative networks that is specifically designed for knowledge representation for recognition of 3-D objects, is introduced. the design criteria, largely influenced...
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VIKNET (visual knowledge network), an extension of associative networks that is specifically designed for knowledge representation for recognition of 3-D objects, is introduced. the design criteria, largely influenced by early visionprocessing, are discussed. VIKNET is formally described as an algebraic structure, with network functions defined on it. the input image, also in the form of a network, is recognized by a partial matching algorithm. A completely worked out example demonstrates the efficacy of the scheme even for shapes subjected to viewing angle transforms.< >
A number of architectures which combine efficient iconic and symbolic processing are reviewed. An approach which enhances the structure of the 2D mesh while still retaining that structure is suggested. the deficiencie...
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A number of architectures which combine efficient iconic and symbolic processing are reviewed. An approach which enhances the structure of the 2D mesh while still retaining that structure is suggested. the deficiencies of the mesh, in its usual form, in terms of symbolic processing are taken as indications of how the enhancement should proceed. the authors identify three orthogonal properties (processor power, processor autonomy, and interprocessor connectivity) which are open to manipulation. On the basis of a number of generic operations, both iconic and symbolic, the effect of varying each of these parameters is examined with emphasis on the requirements for sequences of operations to execute efficiently. An attempt is made to evaluate the cost-effectiveness of the various possibilities.< >
A collection of routing algorithms for the content-addressable array parallel processor (CAAPP) which allow many more classes of interprocessor communication to be executed efficiently than otherwise on machines with ...
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A collection of routing algorithms for the content-addressable array parallel processor (CAAPP) which allow many more classes of interprocessor communication to be executed efficiently than otherwise on machines with conventional mesh-connected topologies is presented. It is shown that routing on the CAAPP can be executed with simplicity and performance similar to that of a dedicated routing network. Experimental results are presented from random permutations as well as from several common machine vision applications.< >
the authors describe how a surface reconstruction algorithm based on minimizing the variation of surface curvature can be used to stabilize and correct the results of local shading analysis. the approach is viewpoint ...
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the authors describe how a surface reconstruction algorithm based on minimizing the variation of surface curvature can be used to stabilize and correct the results of local shading analysis. the approach is viewpoint independent and applicable to any process that can provide estimates of local surface orientation. the assumptions used in formulating the minimization are derived from standard differential geometry. When applied as a second stage of processing after local shading analysis, the algorithm can recover a close approximation of the true surface orientation under realistic assumptions about image noise. Results are presented that show the performance of the algorithm on synthetic and real data. In particular, they demonstrate how this form of reconstruction can compensate for some of the shape distortion incurred in local shading analysis.< >
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