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I've got a Haskell program that is performing non linearly performance wise (worse then O(n)).
I'm trying to investigate whether memoization is taking place on a function, can I verify this? I'm familiar with GHC profiling - but I'm not too sure which values I should be looking at?
A work around is too just plug some values and observe the execution time - but it's not ideal.
668
Most Haskell compilers and interpreters (all of them that I know of actually) do not memoize polymorphic structures, so m2's internal list is recreated every time it's called, where m1's is not.
The trick is to turn a function into a value because, in Haskell, functions are not memoized but values are.
As far as I know there is no automatic memoization in Haskell.
That said there seems to be an optimization in GHC that caches values for parameterless function like the following
rightTriangles = [ (a,b,c) |
c <- [1..],
b <- [1..c],
a <- [1..b],
a^2 + b^2 == c^2]
If you try out the following in GHCi twice, you'll see that the second call ist much faster:
ghci > take 500 rightTriangles
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