707 research outputs found
Automated Circuit Approximation Method Driven by Data Distribution
We propose an application-tailored data-driven fully automated method for
functional approximation of combinational circuits. We demonstrate how an
application-level error metric such as the classification accuracy can be
translated to a component-level error metric needed for an efficient and fast
search in the space of approximate low-level components that are used in the
application. This is possible by employing a weighted mean error distance
(WMED) metric for steering the circuit approximation process which is conducted
by means of genetic programming. WMED introduces a set of weights (calculated
from the data distribution measured on a selected signal in a given
application) determining the importance of each input vector for the
approximation process. The method is evaluated using synthetic benchmarks and
application-specific approximate MAC (multiply-and-accumulate) units that are
designed to provide the best trade-offs between the classification accuracy and
power consumption of two image classifiers based on neural networks.Comment: Accepted for publication at Design, Automation and Test in Europe
(DATE 2019). Florence, Ital
Fusion of imprecise qualitative information
In this paper, we present a new 2-tuple linguistic representation model, i.e. Distribution Function Model (DFM), for combining imprecise qualitative information using fusion rules drawn from Dezert-Smarandache Theory (DSmT) framework. Such new approach allows to preserve the precision and efficiency of the combination of linguistic information in the case of either equidistant or unbalanced label model. Some basic operators on imprecise 2-tuple labels are presented together with their extensions for imprecise 2-tuple labels. We also give simple examples to show how precise and imprecise qualitative information can be combined for reasoning under uncertainty. It is concluded that DSmT can deal efficiently with both precise and imprecise quantitative and qualitative beliefs, which extends the scope of this theory
Privacy Leakages in Approximate Adders
Approximate computing has recently emerged as a promising method to meet the
low power requirements of digital designs. The erroneous outputs produced in
approximate computing can be partially a function of each chip's process
variation. We show that, in such schemes, the erroneous outputs produced on
each chip instance can reveal the identity of the chip that performed the
computation, possibly jeopardizing user privacy. In this work, we perform
simulation experiments on 32-bit Ripple Carry Adders, Carry Lookahead Adders,
and Han-Carlson Adders running at over-scaled operating points. Our results
show that identification is possible, we contrast the identifiability of each
type of adder, and we quantify how success of identification varies with the
extent of over-scaling and noise. Our results are the first to show that
approximate digital computations may compromise privacy. Designers of future
approximate computing systems should be aware of the possible privacy leakages
and decide whether mitigation is warranted in their application.Comment: 2017 IEEE International Symposium on Circuits and Systems (ISCAS
MSB-First Interval-Bounded Variable-Precision RealTime Arithmetic Unit
This paper presents a paradigm of real-time processing on the lowest level of computing systems: the arithmetic unit. The arithmetic unit based on this principle containing addition, subtraction, multiplication and division operations is described. The development of the computation model is based on the Soft Computing and the Imprecise Computation paradigms, combined with the MSBFirst and the Interval Arithmetic techniques. Those paradigms and techniques give the arithmetic unit design the ability to compute with precisions as a function of time available or accuracy needed. The predictability of processing time and result's accuracy are obtained by means of processing granularity of k bits and by using look-up tables. We present an evaluation of the operation in time delay and computation accuracy that shows significant performance improvement over conventional arithmetic unit architecture, that is, the ability to produce intermediate-result during execution time, to give certainty in computation accuracy even before the process finish time by providing two intermediate-results, which act as the lower and upper bound of the real and complete computation result, and finally, gain high computation accuracy from the early time of the execution process
A course on digital electronics based on solving design-oriented exercises by means of a PBL strategy
Recently, new syllabuses are being implemented accordingly to the European Higher Education Area (EHEA) in Spain.
This paper describes the methodology and assessment strategy applied in the subject ‘‘Digital Circuits and Systems’’ (CSD)
in the third semester course in the Telecommunications Engineering degree at the Castelldefels School of Telecommunications
and Aerospace Engineering (EETAC) of the Universitat Polite`cnica de Catalunya (UPC). The course’s main learning
objective is that students be able to analyse and design simple combinational and sequential circuits by means of hardware
description languages for programmable devices and program applications using microcontrollers and C language.
Small groups of two or three students work in cooperation using PBL techniques to solve design-oriented assignments,
while instructors act more as mediators than lecturers in order to facilitate project development and knowledge acquisition.
The experience we describe corresponds to the spring term of 2011, a period in which this methodology was applied to 46
students.
This work compares statistically the influence of the students’ background on their academic performance in our subject.
A significant correlation has been detected between test marks and the final grade, based on continuous assessment.
Students’ opinions have been obtained by means of a survey at the end of the course. Although the high workload and
involvement, because this methodology requires constancy and commitment from the students, most of them have positive
opinions on the development of the subject, due to the fact that they realise that they have put into practice several
competences or cross-curricular skills, while acquiring the course content, and furthermore, most of them have passed the
course, even with higher grades than the ones from other subjects in the same semester.Peer ReviewedPostprint (published version
Satisfiability-Based Methods for Digital Circuit Design, Debug, and Optimization
Designing digital circuits well is notoriously difficult. This difficulty stems in part from the very
many degrees of freedom inherent in circuit design, typically coupled with the need to satisfy
various constraints. In this thesis, we demonstrate how formulations of satisfiability problems
can be used automatically to complete a design, or to find a specific design architecture that
satisfies certain constraints; how these can be used to create, debug, and optimize designs;
and introduce a domain-specific language particularly well-suited for satisfiability-assisted
design, debug, and optimization.
In the first application, we show how explicit uncertainties called âholesâ can both be natural
to use and conducive to the creation of formal satisfiability problems useful for designing
circuits. We further develop a Scala-hosted Domain Specific Language (DSL) with appropriate
syntactic sugar to make design with holes easy and effective.
We then show how, utilizing the same kind of satisfiability formulation, we can automatically
instrument a given buggy design to replace suspicious syntax fragments with potentially-correct alternatives. The satisfiability solver then determines if there is any possible set of
alternative fragments which fix the bug. We also demonstrate that this approach is reasonably
scalable, in part because there is less need for a fully-precise specification in the formulation
of the satisfiability problem.
We then advance beyond mere hole-filling and show how a tight integration of design elaboration with satisfiability solvers allows totally new approaches. To point, we use this tight
integration to create the first known methods to optimize Gate-Level Information Flow Track-
ing (GLIFT) model circuits and to make principled trade-offs in their precision.
Finally, integrating all the previous work, we propose a more powerful DSL specifically designed to address the shortcomings of the first âhole-fillingâ language. This language, which
we call Nasadiya, affords more general integrations of satisfiability into circuit design and optimization, and provides built-in modeling functionality useful for optimizing extra-functional
properties like critical path delay and circuit area. We demonstrate the utility of these features
by implementing an automatic power optimizer for a popular type of parallel prefix adders
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