Jake Gyllenhaal has reportedly split up with model Alyssa Miller after six months of dating, according to Us Weekly. "They fizzled out. It happened a while back — before the holidays. He's back on the scene," a source says. "Things were really good between Jake and Alyssa right up until he had to leave for L.A. to shoot a movie in the fall. Then the distance just really got to them." Reps for Gyllenhaal and Miller did not respond to requests for comment.