基于FPGA的快速中值滤波算法*

针对传统中值滤波算法排序量多、速度慢的缺点,提出了一种基于FPGA的中值滤波快速算法。充分利用两个相邻滤波窗口中的相关排序信息,随着一列新像素的移入,同时更新已有的排序信息,从而完成中值滤波处理。该算法将每个窗口查找中值的比较次数降到很低,达到了快速抑制噪声及保持图像细节的目的。     

Practical fast computation of Zernike moments

The fast computation of Zernike moments from normalized gometric moments has been developed in this paper,The computation is multiplication free and only additions are needed to generate Zernike moments .Geometric moments are generated using Hataming‘s filter up to high orders by a very simple and straightforward computaion scheme.Other kings of monents(e.g.,Legendre,pseudo Zernike)can be computed using the same algorithm after giving the proper transformaitons that state their relations to geometric moments.Proper normaliztions of geometric moments are necessary so that the method can be used in the efficient computation of Zernike moments.To ensure fair comparisons,recursive algorithms are used to generate Zernike polynoials and other coefficients.The computaional complexity model and test programs show that the speed-up factor of the proposed algorithm is superior with respect ot other fast and /or direct computations It perhaps is the first time that Zernike moments can be computed in real time rates,which encourages the use of Zernike moment features in different image retrieval systems that support huge databases such as the XM experimental model stated for the MPEG-7 experimental core.It is concluded that choosing direct copmutation would be impractical.     

Exploring correlation for fast skyline computation

Scaling skyline queries over high-dimensional datasets remains to be challenging due to the fact that most existing algorithms assume dimensional independence when establishing the worst-case complexity by discarding correlation distribution. In this paper, we present HashSkyline, a systematic and correlation-aware approach for scaling skyline queries over high-dimensional datasets with three novel features: First, it offers a fast hash-based method to prune non-skyline points by utilizing data correlation characteristics and speed up the overall skyline evaluation for correlated datasets. Second, we develop \(HashSkyline_{GPU}\), which can dramatically reduce the response time for anti-correlated and independent datasets by capitalizing on the parallel processing power of GPUs. Third, the HashSkyline approach uses the pivot cell-based mechanism combined with the correlation threshold to determine the correlation distribution characteristics for a given dataset, enabling adaptive configuration of HashSkyline for skyline query evaluation by auto-switching of \(HashSkyline_{CPU}\) and \(HashSkyline_{GPU}\). We evaluate the validity of HashSkyline using both synthetic datasets and real datasets. Our experiments show that HashSkyline consumes significantly less pre-processing cost and achieves significantly higher overall query performance, compared to existing state-of-the-art algorithms.     

Evolutionary circuit design for fast FPGA-based classification of network application protocols

The evolutionary design can produce fast and efficient implementations of digital circuits. It is shown in this paper how evolved circuits, optimized for the latency and area, can increase the throughput of a manually designed classifier of application protocols. The classifier is intended for high speed networks operating at 100 Gbps. Because a very low latency is the main design constraint, the classifier is constructed as a combinational circuit in a field programmable gate array (FPGA). The classification is performed using the first packet carrying the application payload. The improvements in latency (and area) obtained by Cartesian genetic programming are validated using a professional FPGA design tool. The quality of classification is evaluated by means of real network data. All results are compared with commonly used classifiers based on regular expressions describing application protocols.     

FPGA-based architecture for the real-time computation of 2-D convolution with large kernel size

Bidimensional convolution is a low-level processing algorithm of interest in many areas, but its high computational cost constrains the size of the kernels, especially in real-time embedded systems. This paper presents a hardware architecture for the FPGA-based implementation of 2-D convolution with medium–large kernels. It is a multiplierless solution based on Distributed Arithmetic implemented using general purpose resources in FPGAs. Our proposal is modular and coefficient independent, so it remains fully flexible and customizable for any application. The architecture design includes a control unit to manage efficiently the operations at the borders of the input array. Results in terms of occupied resources and timing are reported for different configurations. We compare these results with other approaches in the state of the art to validate our approach.     

Fast computation of morphological operations with arbitrary structuring elements

This paper presents a general algorithm that performs basic mathematical morphology operations, like erosions and openings, with any arbitrary shaped structuring element in an efficient way. It is shown that our algorithm has a lower or equal complexity but better computing time than all comparable known methods.     

A fast hybrid computation model for rectum deformation

It is a challenging task to realistically reproduce the complex deformation of soft bio-tissues in a surgical operation, especially when large deformations and movements exist. A hybrid model which we call the beads-on-string model is presented to handle the deformation and collision of the rectum in a virtual surgery simulation system. Specially tailored for this purpose, our model takes multiple layers to capture the dynamics of the rectum in an efficient manner. Inspired by the shape similarity between a rectum with regular bulges and a string of beads, we use a Cosserat rod model, coinciding with the centreline of the rectum, to calculate its deformation subject to external forces. We introduce rigid spheres, analogy to beads, moving along with the rod to approximate the shape of the rectum in handling collision. In addition, the beads (rigid spheres) provide a natural interlayer to map the deformation of the centreline to the associated mesh which presents detailed geometry of the rectum. Our approach is carefully crafted to achieve high computational efficiency and its multi-layer structure is designed to reproduce the physics of the deformation of the rectum.     

一种基于FPGA的直扩系统快速捕获算法

本文提出一种基于FPGA的频域相关的捕获算法。该算法利用快速傅里叶变换(FFT)实现伪码的快速相关,同时利用离散傅里叶变换频移定理,补偿多普勒频偏,实现大多普勒频偏下的快速捕获。仿真以FPGA实现测试表明,该算法在模拟快速移动载体通信环境下,捕获时间小于40ms,漏警概率小于3×10-3,虚警概率小于3×10-6。     

A novel algorithm for fast computation of Zernike moments

Zernike moments (ZMs) have been successfully used in pattern recognition and image analysis due to their good properties of orthogonality and rotation invariance. However, their computation by a direct method is too expensive, which limits the application of ZMs. In this paper, we present a novel algorithm for fast computation of Zernike moments. By using the recursive property of Zernike polynomials, the inter-relationship of the Zernike moments can be established. As a result, the Zernike moment of order n with repetition m, Z_nm, can be expressed as a combination of Z_n−2,m and Z_n−4,m. Based on this relationship, the Zernike moment Z_nm, for n>m, can be deduced from Z_mm. To reduce the computational complexity, we adopt an algorithm known as systolic array for computing these latter moments. Using such a strategy, the multiplication number required in the moment calculation of Z_mm can be decreased significantly. Comparison with known methods shows that our algorithm is as accurate as the existing methods, but is more efficient.     

Theoretical aspects of gray-level morphology

After a brief discussion of the extension of mathematical morphology to complete lattices, the space of gray-level functions is considered and the concept of a threshold set is introduced. It is shown how one can use binary morphological operators and thresholding techniques to build a large class of gray-level morphological operators. Particular attention is given to the class of so-called flat operators, i.e. operators which commute with thresholding. It is also shown how to define dilations and erosions with nonflat structuring elements if the gray-level set is finite. It is reported that mere truncation yields wrong results     

A communication-reduced and computation-balanced framework for fast graph computation

The bulk synchronous parallel (BSP) model is very user friendly for coding and debugging parallel graph algorithms. However, existing BSP-based distributed graph-processing frameworks, such as Pregel, GPS and Giraph, routinely suffer from high communication costs. These high communication costs mainly stem from the fine-grained message-passing communication model. In order to address this problem, we propose a new computation model with low communication costs, called LCC-BSP. We use this model to design and implement a high-performance distributed graph-processing framework called LCC-Graph. This framework eliminates high communication costs in existing distributed graph-processing frameworks. Moreover, LCC-Graph also balances the computation workloads among all compute nodes by optimizing graph partitioning, significantly reducing the computation time for each superstep. Evaluation of LCC-Graph on a 32-node cluster, driven by real-world graph datasets, shows that it significantly outperforms existing distributed graph-processing frameworks in terms of runtime, particularly when the system is supported by a high-bandwidth network. For example, LCC-Graph achieves an order of magnitude performance improvement over GPS and GraphLab.     

A linear quadrilateral shell element with fast stiffness computation

A new quadrilateral shell element with 5/6 nodal degrees of freedom is presented. Assuming linear isotropic elasticity a Hellinger–Reissner functional with independent displacements, rotations and stress resultants is used. Within the mixed formulation the stress resultants are interpolated using five parameters for the membrane forces as well as for the bending moments and four parameters for the shear forces. The hybrid element stiffness matrix resulting from the stationary condition is integrated analytically. This leads to a part obtained by one point integration and a stabilization matrix. The element possesses the correct rank, is free of locking and is applicable within the whole range of thin and thick shells. The in-plane and bending patch tests are fulfilled and the computed numerical examples show that the convergence behaviour of the stress resultants is very good in comparison to comparable existing elements. The essential advantage is the fast stiffness computation due to the analytically integrated matrices.     

图像中值滤波快速计算的符号检验法

在研究图像中值滤波及其快速算法的基础上,设计并实现了一种新的基于符号检验改进算法的中值滤波快速算法。该算法不需要对邻域内的像素值进行排序,消除了耗时的数据移动操作,从而提高了图像处理速度;同时,符号检验改进算法使用相对值作为统计量,考虑了两个总体样本完全一致的情况,解决了符号检验法的不足之处;最后将改进的符号检验法应用于图像中值滤波。算法分析与大量实验结果表明,该算法不仅大幅度提高了图像中值滤波速度,并且比其他几种快速算法更大程度地保留了图像的边缘、轮廓及纹理等各种信息。     

A novel approach to the fast computation of Zernike moments

This paper presents a novel approach to the fast computation of Zernike moments from a digital image. Most existing fast methods for computing Zernike moments have focused on the reduction of the computational complexity of the Zernike 1-D radial polynomials by introducing their recurrence relations. Instead, in our proposed method, we focus on the reduction of the complexity of the computation of the 2-D Zernike basis functions. As Zernike basis functions have specific symmetry or anti-symmetry about the x-axis, the y-axis, the origin, and the straight line y=x, we can generate the Zernike basis functions by only computing one of their octants. As a result, the proposed method makes the computation time eight times faster than existing methods. The proposed method is applicable to the computation of an individual Zernike moment as well as a set of Zernike moments. In addition, when computing a series of Zernike moments, the proposed method can be used with one of the existing fast methods for computing Zernike radial polynomials. This paper also presents an accurate form of Zernike moments for a discrete image function. In the experiments, results show the accuracy of the form for computing discrete Zernike moments and confirm that the proposed method for the fast computation of Zernike moments is much more efficient than existing fast methods in most cases.     

Robust and fast computation of edge characteristics in image sequences

In this paper we consider a non-parametric analytical model of the intensity for a curved edge, and derive the relations between the image data and some local characteristics of the edge, in the discrete case. In order to identify this model we also study how to develop high order non-biased spatial derivative operators, with subpixel accuracy. In fact, this discrete approach corresponds to the notion of spatio-temporal surfaces in the continuous case, and provides a way to obtain some of the spatio-temporal parameters from an image sequence. An implementation is proposed, and experimental data are provided.Computed characteristics are subpixel localization, normal displacement between two frames, orientation and curvature, but the method is easy to extend to other geometrical or dynamical parameters of the edge.Results derived in this paper are always valid for step-like edges, but computation of orientation and curvature are also valid for edges with more general profiles.     

The p-sized partitioning algorithm for fast computation of factorials of numbers

Computing products of large numbers has always been a challenging task in the field of computing. One such example would be the factorial function. Several methods have been implemented to compute this function including naive product, recursive product, Boiten split, and prime factorization, and linear difference. The method presented here is unique in the sense that it exploits finite order differences to reduce the number of multiplications necessary to compute the factorial. The differences generated are regrouped into a new sequence of numbers, which have at most half as many elements of the original sequence. When the terms of this new sequence are multiplied together, the factorial value is obtained. The cardinality of the new sequence can further be reduced by partitioning. The sequence is computed by using several difference tables that assist in establishing the pattern that determines the sequence. An analysis of the algorithm is presented. The analysis shows that the execution time can be reduced significantly by the algorithm presented.