Research Interests
- Task Scheduling and Mapping for Multicore Architectures
- Paralel Algorithm Design
- Reliability Issues for Multicore Architectures, Fault Tolerant Computing
- Workflow Scheduling in Cloud Computing / Fog Computing
- Dynamic Optimization Problems
- Hybrid Evolutionary Algorithms and their applicability on various domains
- Meta-Heuristic and Hyper-Heuristic Techniques
Funded Projects
- Elastik: A Cross-Layer Reliability Optimization Framework for Manycore Architectures
TUBITAK, 1001 Project, Project No: 113E530
Period: 4/2014 – 9/2016
Role: Principal Investigator
Abstract: Modern architectures are vulnerable to soft errors due to shrinking transistor sizes and high frequencies. Cache structures in a multicore system are more vulnerable to soft errors due to high transistor density. Protecting all caches unselectively has notable overhead on performance and energy consumption. In this project, we propose asymmetrically reliable caches to supply reliability need of the system using sufficient additional hardware under the performance and energy constraints. In our reliability optimization framework, a chip multiprocessor is composed of at least one high reliability core which has ECC protection on its L1 cache, and a set of low reliability cores which have no protection on their L1 caches. Application threads are mapped on the different cores in terms of reliability based on their critical data usage. In our framework, reliability-based critical code regions are assumed as the high priority functions which are extracted by examining execution time percentages and call graph, statically. In this system, software threads which execute reliability-based critical code regions are mapped onto the protected cores, whereas the threads which execute non-critical regions are mapped to the unprotected ones, dynamically during the execution. Our framework benefits preserving reliability-based critical regions of the applications exclusively by providing notable power and cost savings with close performance and reliability values for a set of functions reported in experimental results. As part of the project, we propose and evaluate various scheduling algorithms for mapping the application threads on the protected cores. In our first approach, we started with a primitive scheduler which is based on First Come First Served (FCFS) policy. Different types of priority-based scheduling and equal-time based scheduling techniques are proposed and utilized in the later phases of the project.
- Application Scheduling and Optimization for Chip Multiprocessor (CMP) Architectures
TUBITAK 1010 Project, Project No: 108E035
Period: 8/2008 – 6/2011
Role: Principal Investigator
Abstract: In this project, we developed static and dynamic techniques for mapping application threads onto cores of a given chip multiprocessor (CMP) architecture. For static application mapping case, we designed two novel parallel formulations for the Barnes-Hut on the Cell Broadband Engine architecture by considering technical specifications and limitations of the Cell architecture. Our experimental evaluation indicates that this application performs much faster on the Cell architecture compared to the reference architecture, an Intel Xeon based system. Our first system for dynamic application mapping assigns application threads onto cores and maps the data they manipulate onto available on-chip memory components. In addition to the dynamic application mapping approach, a locality-aware dynamic mapping algorithm is proposed in this study, which targets to assign computations with similar data access patterns to the same core. In addition to our performance-aware application mapping techniques, a novel metric called “Thread Vulnerability Factor (TVF)” was proposed and developed as part of this project in order to measure the reliability of multi-threaded applications. The TVF metric measures vulnerability of a thread against transient errors; and the TVF calculation for a given thread (which is typically one of the threads of a multithreaded application) does not depend on its code alone, but also on the codes of the threads that share resources and data with that thread. Due to its efficiency of determining less reliable or less fault tolerant threads of a multithreaded application, our TVF metric will provide a vital role in order to propose reliability-aware application mapping strategies.
- Locating and Utilizing Sensors with Hybrid Evolutionary Algorithms in a Synthetically Generated Landscape
TÜBİTAK 1001 Project, Project No: 106E059
Period: 2/2007 – 11/2009
Role: Principal Investigator
Deploying and configuring multiple sensors for acqusition of a given area is one of the fundamental research areas of researchers from various fields including computer vision, autonomous systems and robotics. In this project, we presented a novel multi-atribute utility theory based model and a framework for determining the types and number of sensors, locating the selected sensors and setting their orientational sensor-specific parameters including heading and tilt angles on a synthetically generated 3-D terrain with multiple objectives. Our model relies on rational trade-off between the three conflicting objectives which are maximizing the coverage area while maintaining the maximum stealth, and minimizing the total acquisition cost of deploying the sensors. In addition to theoretical foundations, we developed a new hybrid evolutionary algorithm for the sensor placement problem. We incorporated new and specialized operators for hybridization, including problem-specific heuristics for initial population generation, intelligent variation operators (Contribution-Based Crossover operator and Proximity-Based Crossover operator) which comprise problem specific knowledge, and a local search phase. The experimental study validates finding the optimal balance among visibility-oriented, stealth-oriented and cost-oriented objectives. In this project, we also developed a new hybrid solution for path planning of moving sensors with different access characteristics including different slopes of climbing and different minimum turning angles.
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Hybrid Solutions for Dynamic Optimization Problems
Marmara University Research Fund Period: 09/2015 -09/2017
Role: Principal Investigator
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Reliability-Aware Core Partitioning Strategies for Multicore Architecture
Marmara University Research Fund, Project No: FEN-A-200611-0210 Period: 7/2011 – 6/2013
Role: Principal Investigator
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Task Scheduling Algorithms for Heterogeneous Environments
Marmara University Research Fund Period: 2000 – 2002
Role: Principal Investigator
