[Haskell-cafe] Strange memory consumption problems in something
that should be tail-recursive
jeff at renci.org
Tue Feb 13 16:05:45 EST 2007
On Tuesday 13 February 2007 15:59, Duncan Coutts wrote:
> On Tue, 2007-02-13 at 15:27 -0500, Jefferson Heard wrote:
> > Hi, I am running the following code against a 210 MB file in an attempt
> > to determine whether I should use alex or whether, since my needs are
> > very performance oriented, I should write a lexer of my own. I thought
> > that everything I'd written here was tail-recursive
> Isn't that exactly the problem - that it's tail recursive? You do not
> want it to be tail recursive since then it must consume the whole input
> before producing any output. You want it to be as lazy as possible so
> that it can start producing tokens as soon as possible without having to
> consume everything.
> If performance is really important to you then you may also want to
> investigate lexing from a lazy ByteString. Alex can now do that (darcs
> version) or you can do it by hand as you're trying now.
Argh, bitten by the scheme bug! Right -- NO tail recursion... So that leaves
me with some rather non-intuitive strategies for achieving execution time
efficiency. Anyone care to point me in the direction of a document on
efficiency in Haskell?
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