1963957
Fast and efficient searches for effective optimization-phase sequences
It has long been known that a fixed ordering of optimization phases will not produce the best code for every application. One approach for addressing this phase-ordering problem is to use an evolutionary algorithm to search for a specific sequence of phases for each module or function. While such searches have been shown to produce more efficient code, the approach can be extremely slow because the application is compiled and possibly executed to evaluate each sequence's effectiveness. Consequently, evolutionary or iterative compilation schemes have been promoted for compilation systems targeting embedded applications where meeting strict constraints on execution time, code size, and power consumption is paramount and longer compilation times may be tolerated in the final stage of development, when an application is compiled one last time and embedded in a product. Unfortunately, even for small embedded applications, the search process can take many hours or even days making the approach less attractive to developers. In this paper, we describe two complementary general approaches for achieving faster searches for effective optimization sequences when using a genetic algorithm. The first approach reduces the search time by avoiding unnecessary executions of the application when possible. Results indicate search time reductions of 62%, on average, often reducing searches from hours to minutes. The second approach modifies the search so fewer generations are required to achieve the same results. Measurements show this approach decreases the average number of required generations by 59%. These improvements have the potential for making evolutionary compilation a viable choice for tuning embedded applications.
12684339
Frequency-shift-invariant orthonormal wavelet packet representations
It is commonly known that wavelet expansions are very sensitive to translation of an input signal due to their dyadic structure. Without proper time alignment of the signal to the decomposition basis vectors, a compact expansion may be unattainable. Recently, work has been done to combat translation sensitivity by determining the best translation-invariant expansion of a signal with respect to a set of bases. However, the dyadic structure of wavelet expansions also results in frequency alignment sensitivity. In this work, we introduce a frequency-shifted wavelet packet library as well as an efficient best basis algorithm for determining the best signal representation among all frequency shifts of a signal.
2859083
A general joint source-channel matching method for wireless video transmission
With the rapid growth of multimedia content in wireless communication, there is an increasing demand for efficient image and video transmission systems. We present a joint source-channel matching scheme for wireless video transmission which jointly optimizes the source and channel coder to yield the optimal transmission quality while satisfying real-time delay and buffer constraints. We utilize a parametric model approach which avoids the necessity of having detailed a priori knowledge of the coders, thus making the scheme applicable to a wide variety of source and channel coder pairs. Simulations show that the scheme yields excellent results and works for several different types of source and channel coders.
6816511
Joint source channel matching for a wireless communications link
Summary form only given. With the rapid growth of wireless communications systems there is an increasing demand for efficient image and video transmission. Significant performance gains can be obtained from joint source channel matching where system resources are assigned based on the tradeoff between data and redundancy. We develop a more general approach for joint source channel matching based on a parametric distortion model that incorporates the flexibility and constraints of both the source and the channel. We use parametric models describing source and channel. We use parametric models describing source and channel characteristics that can be accurately applied to most classes of source and channel coders. To show the generality of our approach, we applied it to the familiar Said-Pearlman progressive image coder with two types of channel coders, a coder with orthogonal symbols of different power, and fixed-rate BPSK modulation overlaid with Reed Solomon codes.
9647930
Cross-layer adaptive video coding to reduce energy on general-purpose processors
Traditionally, video encoders have been designed assuming that the more redundancy is removed, the better the encoder. However, on current laptops, reducing the compression efficiency of the video encoder by reducing the number of instructions used to perform compression can actually reduce the total energy used to encode and transmit a sequence. The correct balance between computation and compression efficiency may change dynamically, motivating adaptive encoders. At the same time, recent general-purpose processors also employ energy-driven adaptations. For best gains, the adaptations in the hardware and application layers must be coordinated. From a system design viewpoint, this coordination must happen through minimal, well-defined interfaces. This paper develops (1) an adaptive video encoder for general-purpose processors that trades computational complexity for compression efficiency to minimize total system energy, and (2) a method for determining the best configuration for such an encoder when running on a processor that is also adaptive. Our adaptive processor employs recent energy saving techniques of dynamic voltage and frequency scaling and architectural adaptation. Using a detailed simulator, we show that our cross-layer adaptive application algorithm reduces energy significantly, when employed on a fixed or adaptive processor.
17269099
Edge detection in ultrasound speckle noise
Presents a statistical approach to edge detection in ultrasound speckle, and uses actual noise statistics to derive an expression for an optimal detection rule. The authors compute the optimal detector for the special case of uncorrelated speckle, and an approximation to the optimal detector for the case when signal-to-noise ratio (SNR) is high. They also discuss a simple sub-optimal detection scheme, and show that its performance is close to that of the optimal uncorrelated speckle detection rule, and surpasses that of the high-SNR approximation except in the case of extremely high SNR, in which case they both perform equally well.<<ETX>>
16917081
Role of Word Sense Disambiguation in Lexical Acquisition: Predicting Semantics from Syntactic Cues
This paper addresses the issue of word-sense ambiguity in extraction from machine-readable resources for the construction of large-scale knowledge sources. We describe two experiments: one which ignored word-sense distinctions, resulting in 6.3% accuracy for semantic classification of verbs based on (Levin, 1993); and one which exploited word-sense distinctions, resulting in 97.9% accuracy. These experiments were dual purpose: (1) to validate the central thesis of the work of (Levin, 1993), i.e., that verb semantics and syntactic behavior are predictably related; (2) to demonstrate that a 15-fold improvement can be achieved in deriving semantic information from syntactic cues if we first divide the syntactic cues into distinct groupings that correlate with different word senses. Finally, we show that we can provide effective acquisition techniques for novel word senses using a combination of online sources.
18506033
Evaluation of voting systems
T he recent spate of security issues and allegations of " lost votes " in the U.S. demonstrates the inadequacy of the standards used to evaluate our election systems. The current standards (the FEC Voting Systems Standards) along with the revision being developed by IEEE 1583 (see the article by Deutsch and Berger in last month's Communications) are poor from another perspective: they establish a single pass/fail threshold for all systems, thereby eliminating incentives for existing suppliers to improve their products and rendering the market unattractive to new entrants. Moreover, they fail to precisely define the properties that should be required of a voting system. Instead, the standards rely on specific designs that are more than 15 years old. These legacy designs handicap promising new approaches, such as the various voter-verified printing schemes. New systems are unnecessarily burdened, while their substantial advantages go unrecognized. A set of well-defined properties would encourage the development and commercialization of better voting systems, especially when combined with objective ways to measure performance with respect to those properties. The overall result would then resemble the quantitative federal ratings for automobiles , where features such as vehicle safety and fuel efficiency form a basis for Consumer Reports-style comparative tables. Similarly, specific performance rating guidelines for different aspects of voting systems would provide meaningful metrics upon which system developers could compete. Decision makers, both regulatory and purchasing, would then be free to establish their own minimums for these metrics. Such a rating system can thus cleanly disentangle the development of the technical evaluation process from the various political and regulatory processes. asked the technical community for assistance in determining a new standard. This community is no stranger to the area of voting system properties and standards: a number of authors have tried to characterize requirements , and, in 2002, the Workshop on Election Standards and Technology addressed similar issues. The performance properties for voting systems might include the following: integrity of the votes (both voter verification, " I can check that my vote was captured correctly " and public verification, " anyone can check that all recorded votes were counted correctly "); ballot secrecy (both voter privacy and resistance to vote selling and coercion); robustness (including resistance to denial of service attacks); usability and accuracy (including access for the disabled); and transparency (both of mechanism and election data). The inherent differences in system architectures can be characterized …
9402109
Toward a Scoring Function for Quality-Driven Machine Translation
We describe how we constructed an automatic scoring function for machine translation quality; this function makes use of arbitrarily many pieces of natural language processing software that has been designed to process English language text. By machine-learning values of functions available inside the software and by constructing functions that yield values based upon the software output, we are able to achieve preliminary, positive results in machine-learning the difference between human-produced English and machine-translation English. We suggest how the scoring function may be used for MT system development.
14721450
Implementation of a block based neural branch predictor
This paper contributes to a dynamic branch predictor algorithm based on a perceptron in two directions: Firstly, a new block form of computation is introduced that reduces theoretically by half the combinational critical path for computing a prediction. Secondly, implementation in FPGA hardware is fully developed for quantitative comparison purposes. FPGA circuits for a one-cycle block predictor produces 1.7 faster clock rates than a direct implementation of the original perceptron predictor. This faster clock allows to realize predictions with longer history lengths for the same hardware budget.
12160909
An Architecture For A Universal Lexicon: A Case Study on Shared Syntactic Information in Japanese, Hindi, Bengali, Greek, and English
Naoyuki Nomura, Douglas A. Jones, Robert C. Berwick Massachusetts Institute of Technology, NE43-802 Artificial Intelligence Laboratory nomura@ai.mit.edu Introduction. Given the prominence of the lexicon in most current linguistic theories (LFG, HPSG, GB), the inventory of language particular information left in the lexicon deserves special attention. Constructing large computerized lexicons remains a difficult problem, building a large array of apparently arbitrary information. This paper shows that this arbitrariness can be constrained more than might have been previously thought. In particular, arbitrariness of argument structure, word sense, and paraphrasability will be shown not only to be constrained, but also to be integrally related. Our (radical) view is that variation of lexical behavior across languages is exactly like lexical variation within languages, specifically, the difference lies in the presence or absence of certain morphemes. For example, the fact that Japanese has richer possibilities in certain verbal patterns is derived solely from its morphological inventory.1 Put another way, language parameters simply are the presence or absence of lexical material in the morphological component. Observed language variation patterns reflect morphological systematicity. The generative machinery for producing argument structure positions is fixed across languages. Linguistic Motivation. A striking example underscoring universality of argument structure is the familiar Spray/Load alternation2, shown in (1). Despite the many surface differences in these data across languages, they share several essential properties. (1) a. b. John loaded the hay on the wagon. John loaded the wagon with the hay. Japanese (2) a. taroo-wa teepu-o boo-ni maita. Taro-NOM tape-ACC stick-DAT wrap-PRF 'Taro wrapped the tape around the stick.'