"Something's going on. It has to do with that number. There's an answer in that number."
Ah, how often have I said something similar? Well, probably not very often, which is why the movie Pi didn't, shall we say, speak to me as a mathematician. On a superficial level, it's cool to see some similarities between a movie protagonist and oneself. Hey, he's a number theorist? I'm a number theorist! Hey, he works with computers? I work with computers! Hey, he's trying to figure out the essential patterns in the stock market to predict exactly what it will do the next day? I own stock! Hey, he plays Go? I know people who play Go!
As you can see, the parallels break down at a certain point. True, the mathematics in here is slightly less flawed than in Sneakers or Good Will Hunting. But to a certain extent that's because there's less attempt at detail here. I didn't feel like I was watching a movie about mathematics; I felt like I was watching a movie about a crazy guy who worked on mathematics.
And that's about it. The movie is rather thinly plotted. Max thinks he can find patterns in the chaos; so too do two groups -- one is some sinister goverment or financial organization, the other a group of Hasidic Jews. He tries, they pursue him. There are a lot of scenes of flashing lights and dissonant noise. They didn't do too much for me.
All in all, it's got some intriguing scenes and themes, but to me it felt like an unpolished, although talent-driven, "art school" flick more than anything.