Department of Information Technology, University of Turku and Turku Centre for Computer Science (TUCS), Lemminkäisenkatu 14 A, 20520 Turku, Finland. tapio.pahikkala@it.utu.fi|Department of Information Technology, University of Turku and Turku Centre for Computer Science (TUCS), Lemminkäisenkatu 14 A, 20520 Turku, Finland. tapio.pahikkala@it.utu.fi|Department of Information Technology, University of Turku and Turku Centre for Computer Science (TUCS), Lemminkäisenkatu 14 A, 20520 Turku, Finland. tapio.pahikkala@it.utu.fi|Department of Information Technology, University of Turku and Turku Centre for Computer Science (TUCS), Lemminkäisenkatu 14 A, 20520 Turku, Finland. tapio.pahikkala@it.utu.fi|Department of Information Technology, University of Turku and Turku Centre for Computer Science (TUCS), Lemminkäisenkatu 14 A, 20520 Turku, Finland. tapio.pahikkala@it.utu.fi