(Wall Street Journal Interactive) Computer driven hedge funds have had a tough time over the past few months, but when the chips were down for global markets in late August, they came into their own. That’s according to J.P. Morgan, which says that as equity indexes around the world plunged in late August on fears that China’s growth would slow, CTAs, or hedge funds that use computer programs to make money out of long-term macro trends, gained about 1%….