KTH Royal Institute of Technology, Swedish e-Science Research Centre, Science for Life Laboratory, School of Computer Science and Communication, Solna, SE-171 77, Sweden.|KTH Royal Institute of Technology, School of Information and Communication Technology, Kista, SE-164 40, Sweden.|KTH Royal Institute of Technology, School of Information and Communication Technology, Kista, SE-164 40, Sweden.|KTH Royal Institute of Technology, Swedish e-Science Research Centre, Science for Life Laboratory, School of Computer Science and Communication, Solna, SE-171 77, Sweden.|Department of Numerical Analysis and Computer Science, Swedish e-Science Research Centre, Science for Life Laboratory, Stockholm University, Stockholm, SE-100 44, Sweden.|KTH Royal Institute of Technology, Laboratory for Communication Networks, School of Electrical Engineering, Stockholm, SE-100 44, Sweden.|Department of Computer Science and Engineering, University of Gothenburg, Gothenburg, SE-411 37, Sweden.|Department of Numerical Analysis and Computer Science, Swedish e-Science Research Centre, Science for Life Laboratory, Stockholm University, Stockholm, SE-100 44, Sweden. arve@nada.su.se.