Re: Re[8]: [Haskell-cafe] Strange type behavior in GHCi 6.4.2

What Kirsten said. I think you can be much more productive in optimizing your code if you actually understand what's going on. I usually don't go as far as looking at compiler intermediate code; I usually stick with profiling (or look at assembly code if it's a really performance critical inner loop). Then you can start optimizing. That can be by changing algorithm, changing data representation, strictness annotations, etc. It can also be by inserting some INLINE or SPECIALIZE pragmas, but that's more rare (don't get me wrong about those pragmas, I introduced them in Haskell with hbc). But I think just adding pragmas willy-nilly is a bad idea; I find that most serious performance problems cannot be solved by those means, instead you need a higher level approach. -- Lennart On Dec 31, 2006, at 11:47 , Kirsten Chevalier wrote:

On 12/31/06, Bulat Ziganshin wrote:

...

this don't say anything place. and these rules have their own source: it's hard to optimize using your path. but when program optimization is just adding a few options/pragmas to the program, it' becomes cheap enough to change these rules. didn't you thought about it?

In my experience, adding pragmas and toying with options without insight into what they do is not "cheap", because it takes up the programmer's time, and time is more important than anything else. Every minute spent typing in pragmas is a minute lost that could have been spent thinking about how to write your code more elegantly, and in my experience -- and again, maybe it's just that I'm slow -- adding pragmas doesn't help. When it comes to inlining and specializing, GHC tends to be smarter than I am. (Once more, maybe it's just that I'm slow.) I'd rather focus my energies on doing the things GHC can't (usually) do, like replacing an O(n^2) algorithm with an O(log n) algorithm.

Cheers, Kirsten

-- Kirsten Chevalier* chevalier@alum.wellesley.edu *Often in error, never in doubt "Happy is all in your head / When you wake up and you're not dead / It's a sign of maturation / That you've lowered your expectations..."-- Barbara Kessler _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe