Jim Simons’ RenTech fund halved its Tesla stake last quarter – and dumped meme stocks GameStop and AMC Renaissance Technologies halved its Tesla stake and exited its GameStop and AMC wagers last quarter. Jim Simons'' quant fund supercharged its bet on Warren Buffett''s Berkshire Hathaway to $605 million. RenTech doubled its Tesla holdings and grew its GameStop wager by 118-fold in the first quarter. Renaissance Technologies halved its Tesla stake, dumped GameStop and AMC Entertainment , and bet big on Warren Buffett''s Berkshire Hathaway in the second quarter, a new SEC filing reveals. RenTech, which ranks among the largest and most successful hedge funds in history , was founded by Jim Simons, a former NSA codebreaker and MIT math professor. The quantitative fund employs algorithms to decide many of its trades, resulting in sweeping changes to its stock portfolio each quarter. Simons'' fund slashed its Tesla holdings by 52%, from 1.6 million shares to 748,000. The value of the position tumbled from $1.7 billion to $504 million, in part because Tesla''s stock price plunged by 38% in the period.