7149054
Minimizing sensitivity to delay variations in high-performance synchronous circuits
This paper investigates retiming and clock skew scheduling for improving the tolerance of synchronous circuits to delay variations. It is shown that when both long and short paths are considered, circuits optimized by the combined application of the two techniques are more tolerant to delay variations than when optimized by either of the two techniques separately. A novel mixed-integer linear programming formulation is given for simultaneous retiming and clock scheduling with a target clock period and tolerance under setup and hold constraints. Experiments with LGSynth93 and ISCAS89 benchmark circuits demonstrate the effectiveness of the combined optimization. For half of the test circuits, tolerance to delay variations increased by at least 23% over the separate application of retiming and clock scheduling. Moreover, for two thirds of the test circuits, maximum tolerance improved by at least 11%.
17545097
Design of Rotary Clock Based Circuits
Rotary clock technique has been shown to reduce the power dissipation of clock distribution by up to 80%. However, to our knowledge, no practical digital synchronous circuit has been designed that utilizes the rotary technique due to the multi-phase nature of rotary clock signals and the strong coupling between a rotary clock network and the circuit it drives. In this paper, we make the first attempt to design rotary based circuit by proposing a unified clock and circuit design methodology. Given a sequential circuit and a clock frequency, our scheme derives a rotary clock network and a functionally equivalent circuit so that they can be integrated to operate reliably at the target frequency. We have applied our scheme to design several rotary clock based DSP modules. Simulation results show that all designs operate correctly with no timing violation. Compared with designs using conventional clock trees, our designs achieve an average clock power saving of more than 70%.
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%.
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%.
5855159
Skew spreading for peak current reduction
This paper presents a circuit optimization technique called skewspreading. Given an edge-triggered sequential circuit, skew spreadingderives the required clock arrival times for all registers so that theskews are distributed evenly in a preselected time window without changing the operating frequency of the circuit. Skew spreading is ideal for peak current reduction, since it distributes clock activities and the ensuing signal activities widely in time. We have developed a skew spreading algorithm and applied it to a suite of benchmark circuits. Simulation results demonstrate that the variance of the resulting skew from the uniform distribution can be reduced to 4% on the average. In comparison to other gate-level peak current reduction techniques, our scheme achieves an average improvement of 17% with a speedup of up to 13.9 times.
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.
35018228
Service-Level Management of Adaptive Distributed Network Applications
The paper is on generic service-level management tools that enable the reconfiguration of a distributed network application whenever there are resource-level changes or failures in the underlying network sub-systems. A network service is provided to client applications through a protocol module, with the latter exercising network infrastructure resources in a manner to meet the client requirements. Client requests for a network service instantiate the underlying protocol module with parameters specified at the service interface level, along with a prescription of critical properties to be enforced therein. At run-time, a management module may automatically monitor the service compliance to client-prescribed requirements, and notify the client whenever a service quality degradation is detected. The paper proposes a ‘function’-based model of service provisioning to realize our management approach. In this model, a service prescription conforms to generic interface templates based on an enumeration of the service attributes visible to clients, and how these attributes logically relate to one another in composing a client-level quality expectation. Our management model is independent of the specifics of problem-domain, which simplifies the development of distributed adaptive applications through a ‘software reuse’ of the management module. The paper presents the case study of an application: CDN, to demonstrate the usefulness of our model.
34468051
Approximation Algorithms for Bi-clustering Problems
One of the main goals in the analysis of microarray data is to identify groups of genes and groups of experimental conditions (including environments, individuals and tissues), that exhibit similar expression patterns. This is the so-called bi-clustering problem. In this paper, we consider two variations of the bi-clustering problem: the Consensus Submatrix Problem and the Bottleneck Submatrix Problem. The input of the problems contains a m×n matrix A and integers l and k. The Consensus Submatrix Problem is to find a l×k submatrix with l<m and k<n and a consensus vector such that the sum of distance between all rows in the submatrix and the vector is minimized. The Bottleneck Submatrix Problem is to find a l×k submatrix with l<m and k<n, an integer d and a center vector such that the distance between every row in the submatrix and the vector is at most d and d is minimized. We show that both problems are NP-hard and give randomized approximation algorithms for special cases of the two problems. Using standard techniques, we can derandomize the algorithms to get polynomial time approximation schemes for the two problems. To our knowledge, this is the first time that approximation algorithms with guaranteed ratio are presented for microarray analysis.
2568010
Stability of nontrivial solution of delay differential equations with state-dependent impulses
This paper considers the stability problem of nontrivial solutions of delay differential equations with state-dependent impulses. By using the concepts of reduced system and quasi-stability, the stability problem of a nontrivial solution of the impulsive delay differential equation with state-dependent impulses is converted to that of the trivial solution of the impulsive delay differential equation with fixed impulses. Several stability criteria are then established utilizing the known results for systems with fixed impulses.
11194956
Fuzzy guaranteed cost control for nonlinear systems with time-varying delay
This paper focuses on the problem of guaranteed cost control for Takagi-Sugeno (T-S) fuzzy systems with time-varying delayed state. A linear quadratic cost function is considered as a performance index of the closed-loop fuzzy system. Then, the guaranteed cost control of the closed-loop fuzzy system is discussed, and the sufficient conditions are provided for the construction of a guaranteed cost controller via state feedback and observer-based output feedback. When these conditions, which are given in terms of the feasibility of linear matrix inequalities (LMIs), are satisfied, the designed state feedback controller and observer-based controller gain matrices can be obtained via a convex optimization problem. Two illustrative examples are provided to demonstrate the effectiveness of the approaches proposed in this paper.
792291
Variable grouping in multivariate time series via correlation
The decomposition of high-dimensional multivariate time series (MTS) into a number of low-dimensional MTS is a useful but challenging task because the number of possible dependencies between variables is likely to be huge. This paper is about a systematic study of the "variable groupings" problem in MTS. In particular, we investigate different methods of utilizing the information regarding correlations among MTS variables. This type of method does not appear to have been studied before. In all, 15 methods are suggested and applied to six datasets where there are identifiable mixed groupings of MTS variables. This paper describes the general methodology, reports extensive experimental results, and concludes with useful insights on the strength and weakness of this type of grouping method.