On Wed, 25 Feb 2009, Luke Palmer wrote:

On Wed, Feb 25, 2009 at 10:38 AM, Dusan Kolar wrote:  I have a function a computation of which is quite expensive, it is recursively dependent on itself with respect to some other function values - we can roughly model its behaviour with fib function (returns n-th number of Fibonacci's sequence). Unfortunately, it is not fib, it is far more complicated. Nevertheless, for demonstration of my question/problem I will use fib, it's quite good.

I suggest using data-memocombinators for this rather than rolling your own.  It accomplishes the same thing, but makes the choice of memo structure independent of the code that uses it (and Memo.integral has asymptotically better performance than a list).

Nice to know that there is a package for this purpose. See also http://haskell.org/haskellwiki/Memoization

Thanks for all the hints and code provided, nevertheless, it implied another questions: 1) Am I right that MemoCombinators can be hardly ever used with hugs? If not, which guidelines to be used for installation... 2) Is there any paper/tutorial/wiki that describes, which local definitions/expressions are "discarded"/"not shared" after/"to the next" computation, that means separated closure is built for them? Dusan Henning Thielemann wrote:

On Wed, 25 Feb 2009, Luke Palmer wrote:

...

On Wed, Feb 25, 2009 at 10:38 AM, Dusan Kolar wrote: I have a function a computation of which is quite expensive, it is recursively dependent on itself with respect to some other function values - we can roughly model its behaviour with fib function (returns n-th number of Fibonacci's sequence). Unfortunately, it is not fib, it is far more complicated. Nevertheless, for demonstration of my question/problem I will use fib, it's quite good.

I suggest using data-memocombinators for this rather than rolling your own. It accomplishes the same thing, but makes the choice of memo structure independent of the code that uses it (and Memo.integral has asymptotically better performance than a list).

Nice to know that there is a package for this purpose. See also http://haskell.org/haskellwiki/Memoization

-- Dusan Kolar tel: +420 54 114 1238 UIFS FIT VUT Brno fax: +420 54 114 1270 Bozetechova 2 e-mail: kolar@fit.vutbr.cz Brno 612 66 Czech Republic --