hello, I think that there are 2 main reasons. The university of Tokyo big computers are from Hitachi and this computation is a visibility selling point for them. To hold that record is a matter of pride too. The second reason is to test the machine. They used(?) arctan formulas which is not the fastest but with it they used a lot of disk I/O and cpu. This is a very good stress test for the machine. I don't know yet if they used a Gauss-Salamin formula and/or one of Borwein's quartic formulas, the first being the fastest known. In any case , to do it 2 times with 2 different formulas and arriving at the same result is the test. What anyone could do to test a big super computer like that ? It would be perhaps interesting to see if we could use the so called Earth Simulator (35 teraflop/s) to compute pi once. Simon Plouffe