By luck or design, Nomura's Simplex Equity Futures Strategy Fund ended the day with a 3.4 percent gain, one of its best results in three months of trading. The tumult has been rough on hedge funds, with a gauge of Japan-focused managers tracked by Eurekahedge Pte dropping 3.5 percent this year. It's often difficult to distinguish AI funds from their more ubiquitous "quantitative" investing precursors, according to Motoyuki Sato, a general manager and researcher at Man Group Japan Ltd., a unit of the world's largest publicly traded hedge fund manager. Simplex Asset Management is one of Japan's fastest-growing money managers, overseeing 560 billion for clients.