Spent the day debugging some digital filter code. Atrociously hard stuff, because the numbers have no rational basis in anything, so I don't understand what they mean (they're just coefficients in a long calculation), and small changes make big disturbances. The hardest part is that when some of the coefficients are non-zero, the system crashes eventually. Maybe. But if the first three number sets are there, the filter seems to work as it's supposed to.