Would it be possible to do your calculations on the data as your worked your way through the data using an array of structs?
Even if you only could load 5,000 or 10,000 structs at a time into the array, that could provide a fast way to do the work, and then just reload the array with the next 5,000 (or whatever your array limit is on your system). Surely faster than straight disk access of the data. adak
