Ece Olcay Gunes

Search algorithms for the multiple constant multiplications problem: Exact and approximate

This article addresses the multiplication of one data sample with multiple constants using addition/subtraction and shift operations, i.e., the multiple constant multiplications (MCM) operation. In the last two decades, many efficient algorithms have been proposed to implement the MCM operation using the fewest number of addition and subtraction operations. However, due to the NP-hardness of the problem, almost all the existing algorithms have been heuristics. The main contribution of this article is the proposal of an exact depth-first search algorithm that, using lower and upper bound values of the search space for the MCM problem instance, finds the minimum solution consuming less computational resources than the previously proposed exact breadth-first search algorithm. We start by describing the exact breadth-first search algorithm that can be applied on real mid-size instances. We also present our recently proposed approximate algorithm that finds solutions close to the minimum and is able to compute better bounds for the MCM problem. The experimental results clearly indicate that the exact depth-first search algorithm can be efficiently applied to large size hard instances that the exact breadth-first search algorithm cannot handle and the heuristics can only find suboptimal solutions.

On the realization of oscillators using state equations

Summary In this work, an extension to the oscillator synthesis method using the state variable technique is presented. It is shown that using suitable block diagrams, which represent the state equations, systematic circuit realizations can be performed. The most critical steps of the presented method are the selection of the suitable characteristic equation and thederivation of the corresponding sub-circuits. The selection criteria of thecharacteristic equations for the realization of single resistance controlled oscillators (SRCOs) are also given. By using the extended state variable synthesis method, SRCOs employing a single current feedback amplifier (CFA)are obtained. Furthermore, a new active element, namely the differentialvoltage current feedback amplifier (DVCFA) is proposed for the realization of oscillators employing only grounded capacitors and new SRCOs employing thisactive element are presented. SPICE simulations and experimental results confirm the operation of the presented oscillators.

An Exact Breadth-First Search Algorithm for the Multiple Constant Multiplications Problem

This paper addresses the multiplication of one data sample with multiple constants using addition/subtraction and shift operations, i.e., the multiple constant multiplications (MCM) problem. The MCM problem finds itself and its variants in many applications, such as digital finite impulse response (FIR) filters, linear signal transforms, and computer arithmetic. Although many efficient algorithms have been proposed to implement the MCM using the fewest number of operations, due to the NP-hardness of the problem, they have been heuristics, i.e., they cannot guarantee the minimum solution. In this work, we propose an exact algorithm based on the breadth-first search that finds the minimum number of operations solution of mid-size MCM instances in a reasonable time. The proposed exact algorithm has been tested on a set of instances including FIR filter and randomly generated instances, and compared with the previously proposed efficient heuristics. It is observed from the experimental results that, even though the previously proposed heuristics obtain similar results with the minimum number of operations solutions, there are instances for which the exact algorithm finds better solutions than the prominent heuristics.

Realization of voltage and current-mode transfer functions using unitygain cells

A synthesis procedure for voltage and current-mode transfer functions using unity-gain current and voltage followers is presented, and two networks that realize the general second-order voltage and current transfer functions are given. For both circuits, the element values are expressed in terms of the second-order transfer functions coefficients. The proposed circuits have low sensitivity characteristics.

An nth-order allpass voltage transfer function synthesis using commercially available active components

A general synthesis procedure for the realisation of an nth-order allpass voltage transfer function using an active RC circuit comprising a commercially available active component current feedback amplifier (CFA, i.e. AD844), which contains a plus-type second generation current conveyor (CCII+) and a unity-gain voltage buffer is presented.

On ear biometrics

Today the most successful biometric based identification technologies such as fingerprint, iris, retina, palm and face recognition are used worldwide in both criminal investigations and high security facilities. These technologies are well-studied, but research shows they have many drawbacks which decrease the success of the methods applied. Ear images are not affected by emotional expression, illumination, aging, poses and alike. In this study principal component analysis (PCA), fisher linear discriminant analysis (FLDA), discriminative common vector analysis (DCVA), and locality preserving projections (LPP) were applied to ear images for personal identification. The error and hit rates of four algorithms were calculated by random subsampling and k-fold cross validation.

Effects of the facial and racial features on gender classification

This paper presents an experimental study on examining the effects of facial and racial features on gender classification. In order to show which facial feature is the most influential for gender classification, parts of several face images, such as, forehead, eyebrows, eyes, nose, lip and chin were masked. For dimension reduction, Principal Component Analysis (PCA) and for determination of gender, Fisher Linear Discriminant (FLD) algorithms were applied to masked face images. Moreover, the effects of racial features on gender classification were studied. Experimental results indicated that the nose is the most influential part for gender classification. Furthermore the gender of the Asian people is more easily distinguished than that of the people of African origin.

Effect of Number Representation on the Achievable Minimum Number of Operations in Multiple Constant Multiplications

In this work, we analyze the effect of representing constants under binary, CSD, and MSD representations on the minimum number of operations required in a multiple constant multiplications problem. To this end, we resort to a recently proposed algorithm that computes the exact minimum solution. To extend the applicability of this algorithm to much larger instances, we propose problem reduction and model simplification techniques that significantly reduce the search space. We have conducted experiments on a rich set of instances including randomly generated and FIR filter instances. The results show that, contrary to common belief, the binary representation clearly yields better solutions than CSD, and even provides slightly better solutions than MSD. Moreover, the superiority of the binary solutions increases as the number and bit-width of the constants increase.

An approximate algorithm for the multiple constant multiplications problem

Multiple constant multiplications (MCM) problem that is to obtain the minimum number of addition/subtraction operations required to implement the constant multiplications finds itself and its variants in many applications, such as finite impulse response (FIR) filters, linear signal transforms, and computer arithmetic. There have been a number of efficient algorithms proposed for the MCM problem. However, due to the NP-hardness of the problem, the proposed algorithms have been heuristics and cannot guarantee the minimum solution. In this paper, we introduce an approximate algorithm that can ensure the minimum solution on more instances than the previously proposed heuristics and can be extended to an exact algorithm using an exhaustive search. The approximate algorithm has been applied on a comprehensive set of instances including FIR filter and randomly generated hard instances, and compared with the previously proposed efficient heuristics. It is observed from the experimental results that the proposed approximate algorithm finds competitive and better results than the prominent heuristics.

Realization of voltage/current-mode filters using four-terminal floating nullors

A signal-flow graph synthesis procedure for generating voltage/current-mode filters using four-terminal floating nullors (FTFNs) is presented. Novel networks which realize second-order voltage/current-mode filters are given. For presented circuits the element values are expressed in terms of second-order transfer function coefficients and they have grounded capacitors.