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991.
Aminollah Mahabadi Hamid Sarbazi-Azad Ebrahim Khodaie Keivan Navi 《The Journal of supercomputing》2008,45(1):1-14
This paper proposes an efficient parallel algorithm for computing Lagrange interpolation on k-ary n-cube networks. This is done using the fact that a k-ary n-cube can be decomposed into n link-disjoint Hamiltonian cycles. Using these n link-disjoint cycles, we interpolate Lagrange polynomial using full bandwidth of the employed network. Communication in the
main phase of the algorithm is based on an all-to-all broadcast algorithm on the n link-disjoint Hamiltonian cycles exploiting all network channels, and thus, resulting in high-efficiency in using network
resources. A performance evaluation of the proposed algorithm reveals an optimum speedup for a typical range of system parameters
used in current state-of-the-art implementations.
相似文献
Hamid Sarbazi-AzadEmail: Email: |
992.
993.
Hamid Noori Farhad Mehdipour Kazuaki Murakami Koji Inoue Morteza Saheb Zamani 《The Journal of supercomputing》2008,45(3):313-340
To improve the performance of embedded processors, an effective technique is collapsing critical computation subgraphs as
application-specific instruction set extensions and executing them on custom functional units. The problem with this approach
is the immense cost and the long times required to design a new processor for each application. As a solution to this issue,
we propose an adaptive extensible processor in which custom instructions (CIs) are generated and added after chip-fabrication.
To support this feature, custom functional units are replaced by a reconfigurable matrix of functional units (FUs). A systematic
quantitative approach is used for determining the appropriate structure of the reconfigurable functional unit (RFU). We also
introduce an integrated framework for generating mappable CIs on the RFU. Using this architecture, performance is improved
by up to 1.33, with an average improvement of 1.16, compared to a 4-issue in-order RISC processor. By partitioning the configuration
memory, detecting similar/subset CIs and merging small CIs, the size of the configuration memory is reduced by 40%. 相似文献
994.
We consider the Sequential Monte Carlo (SMC) method for Bayesian inference applied to the problem of information-theoretic
distributed sensor collaboration in complex environments. The robot kinematics and sensor observation under consideration
are described by nonlinear models. The exact solution to this problem is prohibitively complex due to the nonlinear nature
of the system. The SMC method is, therefore, employed to track the probabilistic kinematics of the robot and to make the corresponding
Bayesian estimates and predictions. To meet the specific requirements inherent in distributed sensors, such as low-communication
consumption and collaborative information processing, we propose a novel SMC solution that makes use of the particle filter
technique for data fusion, and the density tree representation of the a posterior distribution for information exchange between
sensor nodes. Meanwhile, an efficient numerical method is proposed for approximating the information utility in sensor selection.
A further experiment, obtained with a real robot in an indoor environment, illustrates that under the SMC framework, the optimal
sensor selection and collaboration can be implemented naturally, and significant improvement in localization accuracy is achieved
when compared to conventional methods using all sensors. 相似文献
995.
Segment-based adaptive hyper-Erlang model for long-tailed network traffic approximation 总被引:1,自引:1,他引:0
Modeling the long-tailedness property of network traffic with phase-type distributions is a powerful means to facilitate the consequent performance evaluation and queuing based analysis. This paper
improves the recently proposed Fixed Hyper-Erlang model (FHE) by introducing an adaptive framework (Adaptive Hyper-Erlang
model, AHE) to determine the crucially performance-sensitive model parameters. The adaptive model fits long-tailed traffic
data set directly with a mixed Erlang distribution in a new divide-and-conquer manner. Compared with the well-known hyperexponential based models and the Fixed Hyper-Erlang model, the Adaptive Hyper-Erlang
model is more flexible and practicable in addition to its accuracy in fitting the tail behavior.
相似文献
Junfeng WangEmail: |
996.
This paper presents an adaptive robust control method for trajectory tracking and path following of an omni-directional wheeled
mobile platform with actuators’ uncertainties. The polar-space kinematic model of the platform with three independent driving
omnidirectional wheels equally spaced at 120 from one another is briefly introduced, and the dynamic models of the three
uncertain servomotors mounted on the driving wheels are also described. With the platform’s kinematic model and the motors’
dynamic model associated two unknown parameters, the adaptive robust controller is synthesized via the integral backstepping
approach. Computer simulations and experimental results are conducted to show the effectiveness and merits of the proposed
control method in comparison with a conventional PI feedback control method. 相似文献
997.
Jan Rosell Carlos Vázquez Alexander Pérez Pedro Iñiguez 《Journal of Intelligent and Robotic Systems》2008,53(3):223-245
Haptic devices allow a user to feel either reaction forces from virtual interactions or reaction forces reflected from a remote
site during a bilateral teleoperation task. Also, guiding forces can be exerted to train the user in the performance of a
virtual task or to assist him/her to safely teleoperate a robot. The generation of guiding forces relies on the existence
of a motion plan that provides the direction to be followed to reach the goal from any free configuration of the configuration
space (-space). This paper proposes a method to obtain such a plan that interleaves a sampling-based exploration of -space with an efficient computation of harmonic functions. A deterministic sampling sequence (with a bias based on harmonic
function values) is used to obtain a hierarchical cell decomposition model of -space. A harmonic function is iteratively computed over the partially known model using a novel approach. The harmonic function
is the navigation function used as motion plan. The approach has been implemented in a planner (called the Kautham planner) that, given an initial and a goal configuration, provides: (a) a channel of cells connecting the cell that contains
the initial configuration with the cell that contains the goal configuration; (b) two harmonic functions over the whole -space, one that guides motions towards the channel and another that guides motions within the channel towards the goal; and
(c) a path computed over a roadmap built with the free samples of the channel. The harmonic functions and the solution path
are then used to generate the guiding forces for the haptic device. The planning approach is illustrated with examples on
2D and 3D workspaces.
This work was partially supported by the CICYT projects DPI2005-00112 and DPI2007-63665. 相似文献
998.
Uniprocessor schedulability theory made great strides, in part, due to the simplicity of composing the delay of a job from
the execution times of higher-priority jobs that preempt it. In this paper, we bound the end-to-end delay of a job in a multistage
pipeline as a function of job execution times on different stages under preemptive as well as non-preemptive scheduling. We
show that the end-to-end delay is bounded by that of a single virtual “bottleneck” stage plus a small additive component. This contribution effectively transforms the pipeline into a
single stage system. The wealth of schedulability analysis techniques derived for uniprocessors can then be applied to decide
the schedulability of the pipeline. The transformation does not require imposing artificial per-stage deadlines, but rather
models the pipeline as a whole and uses the end-to-end deadlines directly in the single-stage analysis. It also does not make
assumptions on job arrival patterns or periodicity and thus can be applied to periodic and aperiodic tasks alike. We show
through simulations that this approach outperforms previous pipeline schedulability tests except for very short pipelines
or when deadlines are sufficiently large. The reason lies in the way we account for execution overlap among stages. We discuss
how previous approaches account for overlap and point out interesting differences that lead to different performance advantages
in different cases. Further, we also show that in certain cases non-preemptive scheduling can result in higher system utilization
than preemptive scheduling in pipelined systems. We hope that the pipeline delay composition rule, derived in this paper,
may be a step towards a general schedulability analysis foundation for large distributed systems.
相似文献
Tarek AbdelzaherEmail: |
999.
Dynamic memory allocation has been used for decades. However, it has seldom been used in real-time systems since the worst
case of spatial and temporal requirements for allocation and deallocation operations is either unbounded or bounded but with
a very large bound.
In this paper, a new allocator called TLSF (Two Level Segregated Fit) is presented. TLSF is designed and implemented to accommodate
real-time constraints. The proposed allocator exhibits time-bounded behaviour, O(1), and maintains a very good execution time. This paper describes in detail the data structures and functions provided by
TLSF. We also compare TLSF with a representative set of allocators regarding their temporal cost and fragmentation.
Although the paper is mainly focused on timing analysis, a brief study and comparative analysis of fragmentation incurred
by the allocators has been also included in order to provide a global view of the behaviour of the allocators.
The temporal and spatial results showed that TLSF is also a fast allocator and produces a fragmentation close to that caused
by the best existing allocators.
相似文献
Alfons Crespo (Corresponding author)Email: |
1000.
This research introduces a new optimality criterion for motion planning of wheeled mobile robots based on a cost index that assesses the nearness to singularity of forward and
inverse kinematic models. Slip motions, infinite estimation error and impossible control actions are avoided escaping from singularities. In addition, high amplification of wheel velocity errors and high wheel velocity values are
also avoided by moving far from the singularity. The proposed cost index can be used directly to complement path-planning and motion-planning techniques (e.g. tree graphs, roadmaps, etc.) in order to select the optimal collision-free path or trajectory among several possible solutions. To illustrate the applications of the proposed
approach, an industrial forklift, equivalent to a tricycle-like mobile robot, is considered in a simulated environment. In particular, several results are
validated for the proposed optimality criterion, which are extensively compared to those obtained with other classical optimality criteria, such as shortest-path, time-optimal and minimum-energy. 相似文献