Department of Computer Engineering, Middle East Technical University, Ankara, Turkey. ahmet@ceng.metu.edu.tr|Department of Computer Engineering, Middle East Technical University, Ankara, Turkey. ahmet@ceng.metu.edu.tr|Department of Computer Engineering, Middle East Technical University, Ankara, Turkey. ahmet@ceng.metu.edu.tr|Department of Computer Engineering, Middle East Technical University, Ankara, Turkey. ahmet@ceng.metu.edu.tr