I'm trying to optimize some code that processes a bunch of data, basically image pixels, which currently takes on the order of several seconds and seems like it should be much faster (important because it's an interactive application). Coming from C++ I have a good idea in my mind of how I'd write it with low-level operations. I read up on Racket optimization. It is still somewhat unclear to me how Racket deals with fixnums, flonums, unsafe operations, Typed Racket types, and how it all fits together. I chose to optimize my program (partly to learn how) incrementally, trying all the options, timing at every step with debugging info turned off. This worked until I wanted to convert Integers to Fixnums in Typed Racket (which has been giving me much faster results than anything in untyped Racket).
The problem is that I can't find a way to convert a Float to a Fixnum, only to an Integer. None of fl->fx, unsafe-fl->fx, or fl->exact-integer work, as Type Checker tells me they're untyped identifiers. Strangely, it doesn't complain with other things from racket/unsafe/ops and racket/fixnum. Ideally, it'd be nice to have a function that works like a cast in C++, rounding down the float to get an int efficiently. Should I not be trying to use Fixnums? Are they just as efficient as Integers? Using a C module is one possible solution, are there any others? Would love some light shed on this topic. ____________________ Racket Users list: http://lists.racket-lang.org/users
