26613748
A Markov chain sequence generator for power macromodeling
In this paper, we present a novel sequence generator based on a Markov chain model. Specifically, we formulate the problem of generating a sequence of vectors with given average input probability p, average transition density d, and spatial correlation s as a transition matrix computation problem, in which the matrix elements are subject to constraints derived from the specified statistics. We also give a practical heuristic that computes such a matrix and generates a sequence of l n-bit vectors in O(nl + n/sup 2/) time. Derived from a strongly mixing Markov chain, our generator yields binary vector sequences with accurate statistics, high uniformity, and high randomness. Experimental results show that our sequence generator can cover more than 99% of the parameter space. Sequences of 2,000 48-bit vectors are generated in less than 0.05 seconds, with average deviations of the signal statistics p, d, and s equal to 1.6%, 1.8%, and 2.8%, respectively. Our generator enables the detailed study of power macromodeling. Using our tool and the ISCAS-85 benchmark circuits, we have assessed the sensitivity of power dissipation to the three input statistics p, d, and s. Our investigation reveals that power is most sensitive to transition density, while only occasionally exhibiting high sensitivity to signal probability and spatial correlation. Our experiments also show that input signal imbalance can cause estimation errors as high as 100% in extreme cases, although errors are usually within 25%.
13241066
Retiming and clock scheduling for digital circuit optimization
This paper investigates the application of simultaneous retiming and clock scheduling for optimizing synchronous circuits under setup and hold constraints. Two optimization problems are explored: (1) clock period minimization and (2) tolerance maximization to clock-signal delay variations. Exact mixed-integer linear programming formulations and efficient heuristics are given for both problems. When both long and short paths are considered, circuits optimized by the combined application of retiming and clock scheduling can achieve shorter clock periods or demonstrate greater tolerance to clock-signal delay variations than circuits optimized by retiming or clock scheduling. Experiments with benchmark circuits demonstrate the effectiveness of the combined optimization. In comparison with the best result obtained by either of the two optimizations, the joint application of retiming and clock scheduling increased operating speeds by more than 8% on the average. It also increased tolerance to clock delay variations by an average of 12% over a broad range of target clock frequencies. Larger relative improvements were achieved for shorter clock periods, thus suggesting that simultaneous retiming and clock scheduling can play an important role in high-speed design.
62445228
Practical repeater insertion for low power: what repeater library do we need?
This paper investigates the problem of repeater insertion for low power under a given timing budget. A novel repeater insertion algorithm is proposed to compute the optimal repeater number and width in the discrete solution space, as defined by a given repeater library. Using the proposed algorithm, two practical and highly important questions are addressed. Given a certain tolerance to the degradation of repeater power dissipation: 1) how coarse could the repeater size granularity be? 2) What range should repeater widths be in? The experimental results provide valuable insights into repeater library design. Specifically, the investigation reveals that coarse repeater size granularities can be used to reduce the library size by more than 87% with merely a 4% power degradation. Moreover, for two-pin interconnects with various wire lengths and timing targets, the range of optimal repeater sizes for low power is limited, indicating that a low-cost small-size repeater library, if well designed, is adequate to provide high-quality repeater insertion solutions. The proposed scheme can be used in early design stages to generate a compact repeater library that is passed on to other repeater insertion algorithms.
10662727
Power macromodeling of global interconnects considering practical repeater insertion
In this paper, we present a simple yet highly effective power macromodeling technique for global interconnects that considers optimal repeater insertion. Specifically,our model estimates the interconnect power dissipation from the interconnect length, the timing budget, the repeater location flexibility, and the signal activity using an analytical function that is derived for a given repeater library and fabrication technology. In experiments with different standard cell libraries, the average error of our technique is less than 2%.
9790968
Fuzzy approximate disturbance decoupling of MIMO nonlinear systems by backstepping and application to chemical processes
Fuzzy approximate disturbance decoupling concept is introduced for a class of multiple-input-multiple-output (MIMO) nonlinear systems with completely unknown nonlinearities. Based on backstepping technique, a fuzzy almost disturbance decoupling control scheme is proposed. The fuzzy controllers guarantee internal uniform ultimate boundedness of the closed-loop adaptive systems and render a bounded approximate L/sub 2/ gain from the disturbance input to the output. The developed design scheme is applied to control a two continuous stirred tank reactor process. The simulation results illustrate the effectiveness of the method proposed in this paper.
62878
Single-hop probing asymptotics in available bandwidth estimation: sample-path analysis
In this paper, we take the sample-path approach in analyzing the asymptotic behavior of single-hop bandwidth estimation under bursty cross-traffic and show that these results are provably different from those observed under fluid models of prior work. This difference, which we call the probing bias, is one of the previously unknown factors that can cause measurement inaccuracies in available bandwidth estimation. We present an analytical formulation of "packet probing," based on which we derive several major properties of the probing bias. We then experimentally observe the <i>probing bias</i> and investigate its quantitative relationship to several deciding factors such as probing packet size, probing train length, and cross-traffic burstiness. Both our analytical and experimental results show that the probing bias vanishes as the packet-train length or packet size increases. The vanishing rate is decided by the burstiness of cross-traffic.
7819313
Constrained Fairing for Meshes
In this paper, we present a novel fairing algorithm for the removal of noise from uniform triangular meshes without shrinkage and serious distortion. The key feature of this algorithm is to keep all triangle centers invariant at each smoothing step by including some constraints in the energy minimization functional. The constrained functional is then minimized efficiently using an iterative method. Further, we apply this smoothing technique to a multiresolution representation to remove arbitrary levels of detail. A volume-preserving decimation algorithm is presented to generate the multiresolution representation. The experimental results demonstrate the combined algorithm's stability and efficiency.
44693659
Global exponential stability of generalized recurrent neural networks with discrete and distributed delays
This paper is concerned with analysis problem for the global exponential stability of a class of recurrent neural networks (RNNs) with mixed discrete and distributed delays. We first prove the existence and uniqueness of the equilibrium point under mild conditions, assuming neither differentiability nor strict monotonicity for the activation function. Then, by employing a new Lyapunov-Krasovskii functional, a linear matrix inequality (LMI) approach is developed to establish sufficient conditions for the RNNs to be globally exponentially stable. Therefore, the global exponential stability of the delayed RNNs can be easily checked by utilizing the numerically efficient Matlab LMI toolbox, and no tuning of parameters is required. A simulation example is exploited to show the usefulness of the derived LMI-based stability conditions.
6185811
An efficient large deformation method using domain decomposition
Efficiently simulating large deformations of flexible objects is a challenging problem in computer graphics. In this paper, we present a physically based approach to this problem, using the linear elasticity model and a finite elements method. To handle large deformations in the linear elasticity model, we exploit the domain decomposition method, based on the observation that each sub-domain undergoes a relatively small local deformation, involving a global rigid transformation. In order to efficiently solve the deformation at each simulation time step, we pre-compute the object responses in terms of displacement accelerations to the forces acting on each node, yielding a force-displacement matrix. However, the force-displacement matrix could be too large to handle for densely tessellated objects. To address this problem, we present two methods. The first method exploits spatial coherence to compress the force-displacement matrix using the clustered principal component analysis method; and the second method pre-computes only the force-displacement vectors for the boundary vertices of the sub-domains and resorts to the Cholesky factorization to solve the acceleration for the internal vertices of the sub-domains. Finally, we present some experimental results to show the large deformation effects and fast performance on complex large scale objects under interactive user manipulations.