[1] Univ Pisa, Dipartimento Matemat, Via F Buonarroti 1 C, I-I56127 Pisa, Italy
[2] King Abdullah Univ Sci & Technol KAUST, Comp Elect & Math Sci & Engn Div, Thuwal 239556900, Saudi Arabia
[3] Vienna Univ Technol, Inst Anal & Sci Comp, Wiedner Hauptstr 8-10, A-1040 Vienna, Austria