PARIS -- Proud Mary keeps on rollin' -- to her own high-speed beat.A techno music beat.Mary Pierce, the No. 12 seed, on Tuesday routed Austrian Petra Ritter 6-0, 6-2 to reach a Grand Slam semifinal for the first time. In her five matches through the quarterfinals, Pierce has lost only six games.Her five matches have taken a total of four hours, 44 minutes, less than 57 minutes each.Even her next opponent, top seed and defending champion Steffi Graf, is taking notice."She's been playing very, very well, so I've heard ... She's definitely on a roll," Graf said.Pierce attributes some of her improvement to dance classes aimed at helping her footwork."I just started doing it this year," Pierce said. "It is a kind of aerobics ... but not really.''And what kind of music."It is very fast," Pierce said. "Techno music."About as fast as some of her matches. Half of Pierce's 10 sets have been 6-0 scores and Ritter was the first player to take more than a game from Pierce in one set.The previous record of fewest games lost en route to the French Open semifinals was eight, by Andrea Jaeger in 1982, but she had a bye in the first round. Graf, by comparison, has lost 26 games in her five matches here.In addition to the stepwork, Pierce also says she is stronger."I had done weight training since I started playing tennis," Pierce said. "But I have started to do it more seriously. "