http://hackage.haskell.org/cgi-bin/hackage-scripts/package/bytestring-lexing

I’d love to know if that solves your performance issues. (I was able to parse a 50M file of Doubles in around 5seconds, so a 160k CSV parser should be easy).

Not initially, because I was getting an error about not having a debug library for bytestring. But once I installed that library, I profiled it, and most of the time was being spent going ByteString -> String -> Double.

Greg

Reading my comment now it seems as though I was implying that in this particular function unsafePerformIO might be inappropriate: it’s not. You are completely correct to use it here, as strtod is a pure function. I was commenting in a more general way.

Haskell’s type system separates pure functions from impure ones for practical reasons: you can make assumptions about pure functions that you can’t make about impure ones, allowing optimizations and such. I guess all I really wanted to say was that unsafePerformIO discards the information that marks the function as impure, and that’s why it’s called “unsafe”. This doesn’t mean you shouldn’t use it, just that you should be aware that the function you’re calling really does need to be pure, in the sense that its behavior can be completely characterized by its arguments (it doesn’t access or depend on values stored in global variables or internal static buffers) and that it doesn’t produce I/O side-effects or similar.

I guess my point was more to add a word of caution — when using the FFI, make sure that you only use unsafePerformIO in situations when the function truly is pure. If it’s not pure, just don’t use unsafePerformIO — leave the value encapsulated in the IO monad, and Haskell’s type system will take care of making sure that everything happens as it should.

Can you suggest an alternate approach? What can I use instead of unsafePerformIO?

augustss: Got it. Thanks.

Thanks. I made those changes, and although they didn’t effect the execution time, I think they’re logical.

Augustss:

I wondered that myself because the documentation for NOINLINE says something like, “you probably don’t need this.” But then the documentation for unsafePerformIO suggests using that pragma.