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1.
Mesh of trees (MOT) is well known for its small diameter, high bisection width, simple decomposability and area universality.
On the other hand, OTIS (Optical Transpose Interconnection System) provides an efficient optoelectronic model for massively
parallel processing system. In this paper, we present OTIS-MOT as a competent candidate for a two-tier architecture that can
take the advantages of both the OTIS and the MOT. We show that an n4-n^{4}_{-} processor OTIS-MOT has diameter 8log n
∗+1 (The base of the logarithm is assumed to be 2 throughout this paper.) and fault diameter 8log n+2 under single node failure. We establish other topological properties such as bisection width, multiple paths and the modularity.
We show that many communication as well as application algorithms can run on this network in comparable time or even faster
than other similar tree-based two-tier architectures. The communication algorithms including row/column-group broadcast and
one-to-all broadcast are shown to require O(log n) time, multicast in O( n
2log n) time and the bit-reverse permutation in O( n) time. Many parallel algorithms for various problems such as finding polynomial zeros, sales forecasting, matrix-vector multiplication
and the DFT computation are proposed to map in O(log n) time. Sorting and prefix computation are also shown to run in O(log n) time. 相似文献
2.
Evolutionary algorithms are an alternative option to the Boolean synthesis due to that they allow one to create hardware structures that would not be able to be obtained with other techniques. This paper shows a parallel genetic programming (PGP) Boolean synthesis implementation based on a cluster of FPGAs that takes full advantage of parallel programming and hardware/software co-design techniques. The performance of our cluster of FPGAs implementation has been compared with an HPC implementation. The experimental results have shown an excellent behavior in terms of speed up (up to ×500) and in terms of solving the scalability problems of this algorithms present in previous works. 相似文献
3.
This paper presents a framework for allocating radio resources to the Access Points (APs) introducing an Access Point Controller
(APC). Radio resources can be either time slots or subchannels. The APC assigns subchannels to the APs using a dynamic subchannel
allocation scheme. The developed framework evaluates the dynamic subchannel allocation scheme for a downlink multicellular
Orthogonal Frequency Division Multiple Access (OFDMA) system. In the considered system, each AP and the associated Mobile
Terminals (MTs) are not operating on a frequency channel with fixed bandwidth, rather the channel bandwidth for each AP is
dynamically adapted according to the traffic load. The subchannels assignment procedure is based on quality estimations due
to the interference measurements and the current traffic load. The traffic load estimation is realized with the measurement
of the utilization of the assigned radio resources. The reuse partitioning for the radio resources is done by estimating mutual
Signal to Interference Ratio (SIR) of the APs. The developed dynamic subchannel allocation ensures Quality of Service (QoS),
better traffic adaptability, and higher spectrum efficiency with less computational complexity.
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4.
Modern service robots will soon become an essential part of modern society. As they have to move and act in human environments,
it is essential for them to be provided with a fast and reliable tracking system that localizes people in the neighborhood.
It is therefore important to select the most appropriate filter to estimate the position of these persons. This paper presents
three efficient implementations of multisensor-human tracking based on different Bayesian estimators: Extended Kalman Filter
(EKF), Unscented Kalman Filter (UKF) and Sampling Importance Resampling (SIR) particle filter. The system implemented on a
mobile robot is explained, introducing the methods used to detect and estimate the position of multiple people. Then, the
solutions based on the three filters are discussed in detail. Several real experiments are conducted to evaluate their performance,
which is compared in terms of accuracy, robustness and execution time of the estimation. The results show that a solution
based on the UKF can perform as good as particle filters and can be often a better choice when computational efficiency is
a key issue. 相似文献
5.
We propose and analyze in details the revised model of XPROB, an infinite family of pool-based anonymous communication systems
that can be used in various applications including high performance computing environments. XPROB overcomes the limitations
of APROB Channel that only resists a global delaying adversary (GDA). Each instance of XPROB uses a pool mix as its core component
to provide resistance against a global active adversary (GAA), a stronger yet more practical opponent than a GDA. For XPROB,
a GAA can drop messages from users but cannot break the anonymity of the senders of messages. Analysis and experimental evaluations
show that each instance of XPROB provides greater anonymity than APROB Channel for the same traffic load and user behaviors
(rate and number of messages sent). In XPROB, any message can be delivered with high probability within a few rounds after
its arrival into the system; thus, an opponent cannot be certain when a message will be delivered. Furthermore, users can
choose their own preference balance between anonymity and delay. Through the evaluation, we prove that XPROB can provide anonymity
for users in high-performance computing environments. 相似文献
6.
The recent advance of multicore architectures and the deployment of multiprocessors as the mainstream computing platforms have given rise to a new concurrent programming impetus. Software transactional memories (STM) are one of the most promising approaches to take up this challenge. The aim of a STM system is to discharge the application programmer from the management of synchronization when he/she has to write multiprocess programs. His/her task is to decompose his/her program into a set of sequential tasks that access shared objects, and to decompose each task in atomic units of computation. The management of the required synchronization is ensured by the associated STM system. This paper presents two existing STM systems, and a new one based on time-window mechanism. The paper, which focuses mainly on STM principles, has an introductory and survey flavor. 相似文献
7.
This paper proposes a rule-based motion planning system for agent-based crowd simulation, consisting of sets of rules for
both collision avoidance and collision response. In order to avoid an oncoming collision, a set of rules for velocity sampling
and evaluation is proposed, which aims to choose a velocity with an expected time to collision larger than a predefined threshold.
In order to improve the efficiency over existing methods, the sampling procedure terminates upon finding an appropriate velocity.
Moreover, the proposed motion planning system does not guarantee a collision-free movement. In case of collision, another
set of rules is also defined to direct the agent to make a corresponding response. The experiment results show that the proposed
approach can be applied in different scenarios, while making the simulation execution efficient. 相似文献
8.
This paper presents a parameterized shared-memory scheme for parameterized metaheuristics. The use of a parameterized metaheuristic
facilitates experimentation with different metaheuristics and hybridation/combinations to adapt them to the particular problem
we are working with. Due to the large number of experiments necessary for the metaheuristic selection and tuning, parallelism
should be used to reduce the execution time. To obtain parallel versions of the metaheuristics and to adapt them to the characteristics
of the parallel system, a unified parameterized shared-memory scheme is developed. Given a particular computational system
and fixed parameters for the sequential metaheuristic, the appropriate selection of parameters in the unified parallel scheme
eases the development of parallel efficient metaheuristics. 相似文献
9.
Data compression is a well-known method to improve the image composition time of parallel volume rendering on distributed
memory multicomputers. In this paper, we propose an efficient data compression scheme, the template run-length encoding (TRLE)
scheme, for image composition. Given an image with 2 n×2 n pixels, in the TRLE scheme, the image is treated as n× n blocks and each block has 2×2 pixels. Since a pixel can be a blank or non-blank pixel, there 16 templates in a block. To compress an image, the TRLE scheme encodes an image block by block similar to the run-length encoding scheme.
However, the TRLE scheme can filter out or use small space to encode blocks whose four pixels are blank pixels, that is, the
TRLE scheme can encode a partial image according to the shape of non-blank pixels. To evaluate the performance of the TRLE
scheme, we compare the proposed scheme with the BR, the RLE, and the BRLC schemes. Since a data compression scheme needs to
cooperate with some data communication schemes, in the implementation, the binary-swap, the parallel-pipelined, and the rotate-tiling
data communication schemes are used. By combining the four data compression schemes with the three data communication schemes,
we have twelve image composition methods. These twelve methods are implemented on an IBM SP2 parallel machine. Four volume
datasets are used as test samples. The data computation time and the data communication time are measured. The experimental
results show that the TRLE data compression scheme with the rotate-tiling data communication scheme outperforms other eleven
image composition methods for all test samples.
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10.
This paper is concerned with the design of the fault detection systems, into which a residual generation, evaluation and threshold are integrated, for linear discrete time-varying processes over a finite horizon. In the proposed design scheme, the residual generation is realised in the context of H∞ fault estimation with a prescribed attenuation level. This attenuation level is minimised by using the Krein-space linear estimation theory and, subsequently, an H∞ fault estimator with the minimum attenuation level is designed in terms of the solution to a set of Riccati-like recursions. For the residual evaluation and decision making purpose, the false alarm rate and fault detection rate indicators are introduced in the norm-based framework, which is integrated into the decision making procedure. For the online computations of the false alarm rate and fault detection rate indicators, further estimates delivered by the H∞ fault estimator are applied without additional (online) computations. By means of checking the change in the false alarm rate and fault detection rate indicators, a decision is then made. In this way, the fault detection performance can be significantly improved. Finally, one application example is exploited to demonstrate the application of the proposed integrated fault detection and performance evaluation schemes. 相似文献
12.
Traditional frequent pattern mining methods consider an equal profit/weight for all items and only binary occurrences (0/1)
of the items in transactions. High utility pattern mining becomes a very important research issue in data mining by considering
the non-binary frequency values of items in transactions and different profit values for each item. However, most of the existing
high utility pattern mining algorithms suffer in the level-wise candidate generation-and-test problem and generate too many
candidate patterns. Moreover, they need several database scans which are directly dependent on the maximum candidate length.
In this paper, we present a novel tree-based candidate pruning technique, called HUC-Prune (High Utility Candidates Prune),
to solve these problems. Our technique uses a novel tree structure, called HUC-tree (High Utility Candidates tree), to capture
important utility information of the candidate patterns. HUC-Prune avoids the level-wise candidate generation process by adopting
a pattern growth approach. In contrast to the existing algorithms, its number of database scans is completely independent
of the maximum candidate length. Extensive experimental results show that our algorithm is very efficient for high utility
pattern mining and it outperforms the existing algorithms. 相似文献
13.
Recently, several standards have emerged for ontology markup languages that can be used to formalize all kinds of knowledge.
However, there are no widely accepted standards yet that define APIs to manage ontological data. Processing ontological information
still suffers from the heterogeneity imposed by the plethora of available ontology management systems. Moreover, ubiquitous
computing environments usually comprise software components written in a variety of different programming languages, which
makes it particularly difficult to establish a common ontology management API with programming language agnostic semantics.
We implemented an ontological Knowledge Base Server, which can expose the functionality of arbitrary off-the-shelf ontology
management systems via a formally specified and well defined API. A case study was carried out in order to demonstrate the
feasibility of our approach to use a formally specified ontology management API to implement a registry for ubiquitous computing
systems. 相似文献
14.
In many engineering applications concerning the recovery of signals from noisy observations, a common approach consists in
adopting autoregressive (AR) models. This paper is concerned with not only the estimation of multichannel autoregressive (MAR)
model parameters but also the recovery of signals. A new noise compensated parameter estimation scheme is introduced in this
paper. It contains an advanced least square vector (ALSV) algorithm which not only keeps the advantage of blindly estimating
the MAR parameters and the variance-covariance matrix of observation noises, but also aims at ensuring the variance-covariance
matrix to be symmetric in each iterative procedure. Moreover, the estimation of variance-covariance matrix of input noise
is proposed, and then we form an optimal filtering to recover the signals. In the numerical simulations, the estimation performance
of the ALSV estimation algorithm significantly outperforms that of other existed methods. Moreover, the optimal filtering
based on the ALSV algorithm leads to more accurate recovery of the true signals. 相似文献
15.
We examine the class of multi-linear representations (MLR) for expressing probability distributions over discrete variables. Recently, MLR have been considered as intermediate representations that facilitate inference in distributions represented as graphical models. We show that MLR is an expressive representation of discrete distributions and can be used to concisely represent classes of distributions which have exponential size in other commonly used representations, while supporting probabilistic inference in time linear in the size of the representation. Our key contribution is presenting techniques for learning bounded-size distributions represented using MLR, which support efficient probabilistic inference. We demonstrate experimentally that the MLR representations we learn support accurate and very efficient inference. 相似文献
16.
This study evaluates the capacity of the Internet to enhance development in emerging regions through Sen's freedom perspective. The paper begins with a qualitative evaluation of the Internet's potential as a freedom enhancer through examples and literature study. It then presents a quantitative evaluation based on web access logs obtained from the AirJaldi network in rural India. We categorize the data based on Sen's freedoms to contribute an information and communication technology-freedom taxonomy and note the challenges in doing so. The usage logs indicate that indeed users may have experienced enhancement in all of Sen's freedom categories; yet our qualitative evaluation suggests there is much unexploited potential. We conclude that it is important to look at the Internet-based Information and Communication Technologies for Development (ICTD) projects through Sen's freedom lens and call for such projects to be evaluated based on these broad freedom goals rather than on focused development goals. 相似文献
17.
Besides classical point based surface design, sphere based creation of characters and other surfaces has been introduced by some of the recently developed modeling tools in computer graphics. ZSpheres ® by Pixologic, or Spore™ by Electronic Arts are just two prominent examples of these softwares. In this paper we introduce a new sphere based modeling tool, which allows us to create smooth, tubular-like surfaces by skinning a user-defined set of spheres. The main advantage of the new method is to provide a parametric surface with more natural and smoother shape, especially at the connection of branches than the surfaces provided by the existing softwares and methods. 相似文献
18.
As typical wireless sensor networks (WSNs) have resource limitations, predistribution of secret keys is possibly the most
practical approach for secure network communications. In this paper, we propose a key management scheme based on random key
predistribution for heterogeneous wireless sensor networks (HSNs). As large-scale homogeneous networks suffer from high costs
of communication, computation, and storage requirements, the HSNs are preferred because they provide better performance and
security solutions for scalable applications in dynamic environments. We consider hierarchical HSN consisting of a small number
high-end sensors and a large number of low-end sensors. To address storage overhead problem in the constraint sensor nodes,
we incorporate a key generation process, where instead of generating a large pool of random keys, a key pool is represented
by a small number of generation keys. For a given generation key and a publicly known seed value, a keyed-hash function generates
a key chain; these key chains collectively make a key pool. As dynamic network topology is native to WSNs, the proposed scheme
allows dynamic addition and removal of nodes. This paper also reports the implementation and the performance of the proposed
scheme on Crossbow’s MicaZ motes running TinyOS. The results indicate that the proposed scheme can be applied efficiently
in resource-constrained sensor networks. We evaluate the computation and storage costs of two keyed-hash algorithms for key
chain generation, HMAC-SHA1 and HMAC-MD5.
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19.
Early assessment of the energy performance of buildings (EPB) is focused in this study. This task is carried out by predicting the cooling load (CL) in a residential building. To this end, due to the drawbacks of neural computing approaches (e.g., local minima), a novel metaheuristic technique, namely teaching–learning-based optimization (TLBO) is employed to modify a multi-layer perceptron neural network (MLPNN). The complexity of the proposed model is also optimized by a trial and error process. Evaluating the results revealed a high efficiency for this scheme. In this sense, the prediction error of the MLPNN was reduced by around 20%, and the correlation between the measured and forecasted CLs rose from 0.8875 to 0.9207. It was also deduced that the TLBO outperforms two benchmark optimizers of cuckoo optimization algorithm (COA) and league championship algorithm (LCA) in terms of both modeling accuracy and network complexity. Moreover, the TLBO-MLP emerged as the most time-effective hybrid as it required considerably lower computation time than COA-MLP and LCA-MLP. Regarding these advantages, the proposed model can be promisingly used for early assessment of EPB in practice. 相似文献
20.
Service-oriented architecture (SOA), workflow, the Semantic Web, and Grid computing are key enabling information technologies in the development of increasingly sophisticated e-Science infrastructures and application platforms. While the emergence of Cloud computing as a new computing paradigm has provided new directions and opportunities for e-Science infrastructure development, it also presents some challenges. Scientific research is increasingly finding that it is difficult to handle “big data” using traditional data processing techniques. Such challenges demonstrate the need for a comprehensive analysis on using the above-mentioned informatics techniques to develop appropriate e-Science infrastructure and platforms in the context of Cloud computing. This survey paper describes recent research advances in applying informatics techniques to facilitate scientific research particularly from the Cloud computing perspective. Our particular contributions include identifying associated research challenges and opportunities, presenting lessons learned, and describing our future vision for applying Cloud computing to e-Science. We believe our research findings can help indicate the future trend of e-Science, and can inform funding and research directions in how to more appropriately employ computing technologies in scientific research. We point out the open research issues hoping to spark new development and innovation in the e-Science field. 相似文献
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