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LowPower Optimization by Smart BitWidth Allocation in a SystemCBased ASIC Design Environment
"... Abstract—The modern era of embedded system design is geared toward the design of lowpower systems. One way to reduce power in an applicationspecified integrated circuit (ASIC) implementation is to reduce the bitwidth precision of its computation units. This paper describes algorithms to optimize ..."
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Abstract—The modern era of embedded system design is geared toward the design of lowpower systems. One way to reduce power in an applicationspecified integrated circuit (ASIC) implementation is to reduce the bitwidth precision of its computation units. This paper describes algorithms to optimize the bit widths of fixedpoint variables for low power in a SystemCbased ASIC design environment. We propose an optimal bitwidth allocation algorithm for two variables and a greedy heuristic that works for any number of variables. The algorithms are used in the automation of converting floatingpoint SystemC programs into ASIC synthesizable SystemC programs. Expected inputs are profiled to estimate errors in the finite precision conversions. Experimental results for the tradeoffs between quantization error, power consumption, and hardware resources used are reported on a set of four SystemC benchmarks that are mapped onto a 0.18µmASIC cell library from Artisan Components. We demonstrate that it is possible to reduce the power consumption by 50 % on the average by allowing roundoff errors to increase from 0.5 % to 1%. Index Terms—Fixedpoint arithmetic, highlevel synthesis, lowpower design, quantization.
ANALYTICAL ACCURACY EVALUATION OF FIXEDPOINT SYSTEMS
"... To satisfy cost constraints, application implementation in embedded systems requires fixedpoint arithmetic. Thus, applications defined in floatingpoint arithmetic must be converted into a fixedpoint specification. This conversion requires accuracy evaluation to ensure algorithm integrity. Indeed, ..."
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To satisfy cost constraints, application implementation in embedded systems requires fixedpoint arithmetic. Thus, applications defined in floatingpoint arithmetic must be converted into a fixedpoint specification. This conversion requires accuracy evaluation to ensure algorithm integrity. Indeed, fixedpoint arithmetic generates quantization noises due to some bits elimination during a cast operation. These noises propagate through the system and modify computing accuracy. In this paper, an accuracy evaluation model based on an analytical approach is presented and valid for all systems including arithmetic operations. The LMS algorithm example is developed and its validity is verified through experimentations. 1.
Systematic testing for control applications
 In MEMOCODE
, 2010
"... Abstract—Software controllers for physical processes are at the core of many safetycritical systems such as avionics, automotive engine control, and process control. Despite their importance, the design and implementation of software controllers remains an art form; dependability is generally poor, ..."
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Abstract—Software controllers for physical processes are at the core of many safetycritical systems such as avionics, automotive engine control, and process control. Despite their importance, the design and implementation of software controllers remains an art form; dependability is generally poor, and the cost of verifying systems is prohibitive. We illustrate the potential of applying program analysis tools on problems in controller design and implementation by focusing on concolic execution, a technique for systematic testing for software. In particular, we demonstrate how a concolic execution tool can be modified to automatically analyze controller implementations and (a) produce test cases achieving a coverage goal, (b) synthesize ranges for controller variables that can be used to allocate bits in a fixedpoint implementation, and (c) verify robustness of an implementation under input uncertainties. We have implemented these algorithms on top of the Splat test generation tool and have carried out preliminary experiments on control software that demonstrates feasibility of the techniques. I.
Testbeds and rapid prototyping in wireless system design
 EURASIP Newsletter
, 2006
"... This tutorial paper gives an overview of requirements on testbeds and rapid prototyping suitable for MIMO transmissions. Testbeds support realtime transmissions over the air and thus allow for experimenting with true physical channels, including also an analog frontend. This makes the transmission ..."
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This tutorial paper gives an overview of requirements on testbeds and rapid prototyping suitable for MIMO transmissions. Testbeds support realtime transmissions over the air and thus allow for experimenting with true physical channels, including also an analog frontend. This makes the transmission process very realistic. On the other hand, rapid prototyping allows for sketching transmitter and receiver hardware architectures of future products. Thus, rapid prototyping is very close to the design of a final product, derisking its financial investment. Several experiment examples demonstrate how testbeds and prototypes can support system design significantly.
Analytical approach for numerical accuracy estimation of fixedpoint systems based on smooth operations
 Transactions on Circuits and Systems I
, 2012
"... Abstract—In embedded systems using fixedpoint arithmetic, converting applications into fixedpoint representations requires a fast and efficient accuracy evaluation. This paper presents a new analytical approach to determine an estimation of the numerical accuracy of a fixedpoint system, which is ..."
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Abstract—In embedded systems using fixedpoint arithmetic, converting applications into fixedpoint representations requires a fast and efficient accuracy evaluation. This paper presents a new analytical approach to determine an estimation of the numerical accuracy of a fixedpoint system, which is accurate and valid for all systems formulated with smooth operations (e.g. additions, subtractions, multiplications and divisions). The mathematical expression of the system output noise power is determined using matrices to obtain more compact expressions. The proposed approach is based on the determination of the timevarying impulseresponse of the system. To speedup computation of the expressions, the impulse response is modelled using a linear prediction approach. The approach is illustrated in the general case of timevarying recursive systems by the Least Mean Square (LMS) algorithm example. Experiments on various and representative applications show the fixedpoint accuracy estimation quality of the proposed approach. Moreover, the approach using the linearprediction approximation is very fast even for recursive systems. A significant speedup compared to the best known accuracy evaluation approaches is measured even for the most complex benchmarks. Index Terms—Fixedpoint arithmetic, quantization noises, adaptive filters, accuracy evaluation I.
Synthesis of FixedPoint Programs
"... Several problems in the implementations of control systems, signalprocessing systems, and scientific computing systems reduce to compiling a polynomial expression over the reals into an imperative program using fixedpoint arithmetic. Fixedpoint arithmetic only approximates real values, and its o ..."
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Several problems in the implementations of control systems, signalprocessing systems, and scientific computing systems reduce to compiling a polynomial expression over the reals into an imperative program using fixedpoint arithmetic. Fixedpoint arithmetic only approximates real values, and its operators do not have the fundamental properties of real arithmetic, such as associativity. Consequently, a naive compilation process can yield a program that significantly deviates from the real polynomial, whereas a different order of evaluation can result in a program that is close to the real value on all inputs in its domain. We present a compilation scheme for realvalued arithmetic expressions to fixedpoint arithmetic programs. Given a realvalued polynomial expression t, we find an expression t ′ that is equivalent to t over the reals, but whose implementation as a series of fixedpoint operations minimizes the error between the fixedpoint value and the value of t over the space of all inputs. We show that the corresponding decision problem, checking whether there is an implementation t ′ of t whose error is less than a given constant, is NPhard. We then propose a solution technique based on genetic programming. Our technique evaluates the fitness of each candidate program using a static analysis based on affine arithmetic. We show that our tool can significantly reduce the error in the fixedpoint implementation on a set of linear control system benchmarks. For example, our tool found implementations whose errors are only one half of the errors in the original fixedpoint expressions.
PARETO FRONT GENERATION FOR A TRADEOFF BETWEEN AREA AND TIMING
"... Different implementation possibilities of an algorithm into hardware offer a variety of design solutions. Only best solutions so called pareto optimal solutions are for design decision of interest. Heuristic methods are preferred for the generation of these pareto optimal solutions, because exhausti ..."
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Different implementation possibilities of an algorithm into hardware offer a variety of design solutions. Only best solutions so called pareto optimal solutions are for design decision of interest. Heuristic methods are preferred for the generation of these pareto optimal solutions, because exhaustive search methods cannot efficiently cope with this problem. This paper describes the mapping of this problem to a genetic algorithm. Further the generation of pareto optimal solutions is presented within an example. 1.
Efficient Design Methods for Embedded Communication Systems
"... Nowadays, design of embedded systems is confronted with complex signal processing algorithms and a multitude of computational intensive multimedia applications, while time to product launch has been extremely reduced. Especially in the wireless domain, those challenges are stacked with tough require ..."
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Nowadays, design of embedded systems is confronted with complex signal processing algorithms and a multitude of computational intensive multimedia applications, while time to product launch has been extremely reduced. Especially in the wireless domain, those challenges are stacked with tough requirements on power consumption and chip size. Unfortunately, design productivity did not undergo a similar progression, and therefore fails to cope with the heterogeneity of modern architectures. Electronic design automation tools exhibit deep gaps in the design flow like highlevel characterization of algorithms, floatingpoint to fixedpoint conversion, hardware/software partitioning, and virtual prototyping. This tutorial paper surveys several promising approaches to solve the widespread design problems in this field. An overview over consistent design methodologies that establish a framework for connecting the different design tasks is given. This is followed by a discussion of solutions for the integrated automation of specific design tasks. Copyright © 2006 M. Holzer et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1.
MODELBASED PRECISION ANALYSIS AND OPTIMIZATION FOR DIGITAL SIGNAL PROCESSORS
"... Embedded signal processing has witnessed explosive growth in recent years in both scientific and consumer applications, driving the need for complex, highperformance signal processing systems that are largely application driven. In order to efficiently implement these systems on programmable platfo ..."
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Embedded signal processing has witnessed explosive growth in recent years in both scientific and consumer applications, driving the need for complex, highperformance signal processing systems that are largely application driven. In order to efficiently implement these systems on programmable platforms such as digital signal processors (DSPs), it is important to analyze and optimize the application design from early stages of the design process. A key performance concern for designers is choosing the data format. In this work, we propose a systematic and efficient design flow involving modelbased design to analyze application data sets and precision requirements. We demonstrate this design flow with an exploration study into the required precision for eigenvalue decomposition (EVD) using the Jacobi algorithm. We demonstrate that with a high degree of structured analysis and automation, we are able to analyze the data set to derive an efficient data format, and optimize important parts of the algorithm with respect to precision. 1.
Hardware/Software Partitioning of Floating Point Software Applications to FixedPointed Coprocessor Circuits
 Embedded System Weeks CODES+ISSS Atlanta
, 2008
"... ABSTRACT General Terms Design, Performance. Keywords Hardware/software partitioning, floating point to fixed conversion, floating point, fixed point. ..."
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ABSTRACT General Terms Design, Performance. Keywords Hardware/software partitioning, floating point to fixed conversion, floating point, fixed point.