Person: TOPCUOĞLU, HALUK RAHMİ
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TOPCUOĞLU
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HALUK RAHMİ
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Publication Open Access Network Congestion Aware Multiobjective Task Scheduling in Heterogeneous Fog Environments(2023-01-01) TOPCUOĞLU, HALUK RAHMİ; Altin L., TOPCUOĞLU H. R., Gurgen F. S.Task scheduling on fog environments surges new challenges compared to scheduling on conventional cloud computing. Various levels of heterogeneity and dynamism cause task scheduling problem is more challenging for fog computing. In this study, we present a multiobjective task scheduling model with a total of five objectives and propose a multiobjective multirank (MOMRank) scheduling algorithm for fog computing. The performance of the proposed strategy is assessed with well-known multiobjective metaheuristics [the nondominated sorting genetic algorithm II (NSGA-II) and the Strength Pareto Evolutionary Algorithm 2 (SPEA2)] and a widely used algorithm from the literature, the multiobjective heterogeneous earliest finish time (MOHEFT) algorithm using three common multiobjective metrics. Additionally, we incorporate two task clustering mechanisms to the algorithms in order to improve data transmissions on interconnection networks. Results of empirical evaluations given in performance profiles over all problem instances validate significance of both our algorithm and the integrated extensions for diminishing data transfer costs.Publication Open Access Studying error propagation on application data structure and hardware(2022-11-01) ÖZTÜRK, ZUHAL; TOPCUOĞLU, HALUK RAHMİ; ÖZTÜRK Z., TOPCUOĞLU H. R., Kandemir M. T.As technology scales, transistors become smaller and aggressive power optimization techniques combined with high operation frequencies and performance-enhancing microarchitectural techniques are employed to achieve increasingly higher performance and power efficiencies. Unfortunately, these developments make the modern systems more vulnerable to soft errors, which are becoming a critical issues in both hardware and software domains. Motivated by this observation, in this work, we propose, implement, and evaluate two error propagation metrics in order to characterize error propagation at both software and hardware levels. The first metric aims to measure error propagation on program data structures, whereas the second one measures the fraction of corrupted locations in the cache memory structure for a given period of time. We evaluate our proposed metrics by performing an empirical study of two application programs using both single-threaded and multi-threaded executions, and varying various experimental parameters such as thread count, error rate, location of errors, and architectural parameters. Our extensive experimental analysis reveals that error propagation over program data structures is highly dependent on application behavior.Further, depending on the cache parameters used, propagation of errors on cache can exhibit different patterns. This paper also discusses how our observed error propagation trends in program data structures and data caches are correlated with each other, focusing in particular on the differences in error propagation speeds in application data structures and data caches.Publication Open Access Dynamic multi-objective evolutionary algorithms in noisy environments(2023-07-01) TOPCUOĞLU, HALUK RAHMİ; Sahmoud S., TOPCUOĞLU H. R.Real-world multi-objective optimization problems encounter different types of uncertainty that may affect the quality of solutions. One common type is the stochastic noise that contaminates the objective functions. Another type of uncertainty is the different forms of dynamism including changes in the objective functions. Although related work in the literature targets only a single type, in this paper, we study Dynamic Multi-objective Optimization problems (DMOPs) contaminated with stochastic noises by dealing with the two types of uncertainty simultaneously. In such problems, handling uncertainty becomes a critical issue since the evolutionary process should be able to distinguish between changes that come from noise and real environmental changes that resulted from different forms of dynamism. To study both noisy and dynamic environments, we propose a flexible mechanism to incorporate noise into the DMOPs. Two novel techniques called Multi-Sensor Detection Mechanism (MSD) and Welford-Based Detection Mechanism (WBD) are proposed to differentiate between real change points and noise points. The proposed techniques are incorporated into a set of Dynamic Multi-objective Evolutionary Algorithms (DMOEAs) to analyze their impact. Our empirical study reveals the effectiveness of the proposed techniques for isolating noise from real dynamic changes and diminishing the noise effect on performance.Publication Metadata only A new prediction-based algorithm for dynamic multi-objective optimization problems(2023-01-01) TOPCUOĞLU, HALUK RAHMİ; Karkazan K., TOPCUOĞLU H. R., Sahmoud S.The mechanism for reacting to the changes in an environment when detected is the key issue that distinguishes various algorithms proposed for dynamic multi-objective optimization problems (DMOPs). The severity of change is a significant approach to identify the dynamic characteristics of DMOPs. In this paper, a prediction-based strategy based on utilizing the degree of the changes is presented to address environmental changes. In case of a change detection in the given DMOP, the severity of change is evaluated and an appropriate reaction mechanism is followed based on the degree of the observed change. To accelerate the convergence process, the algorithm may respond multiple times for the same change. The performance of our algorithm is evaluated by comparing it with dynamic multi-objective evolutionary algorithms using six benchmarks. The effectiveness of our algorithm is demonstrated in the experimental study where it outperforms other compared algorithms in most of the tested instances considered.