[1] Univ Innsbruck, Dept Comp Sci, Technikerstr 21A, A-6020 Innsbruck, Austria
[2] Univ Cambridge, Comp Lab, GE21,William Gates Bldg,JJ Thomson Ave, Cambridge CB3 0FD, England
[3] Tech Univ Munich, Dept Informat, Boltzmannstr 3, D-85748 Garching, Germany
[4] Hebew Univ Jerusalem, IL-91904 Jerusalem, Israel
[5] Univ Grenoble Alpes, CNRS, INRIA, Grenoble INP,LIG, Grenoble, France
[6] MPI SWS, Saarbrucken, Germany
[7] Univ Calif Berkeley, Cory Hall, Berkeley, CA 94720 USA
[8] Lab Informat Grenoble, Batiment IMAG,700 Ave Cent,Domaine Univ, F-38400 St Martin Dheres, France