[Haskell-cafe] Fannkuch Entry

[Sebastian Sylvan]

On 1/6/06, David F. Place <d at vidplace.com> wrote:
> Hi All,
>
> I've been enjoying following the thread about the "shootout" programs
> and trying to understand the performance of the entries, especially
> the Fannkuch benchmark.  I've been comparing Sebastion's and
> Bertram's proposals found on the wiki.   On my machine (PowerBook g4
> (512M), GHC 6.4.1), Bertam's is about 3x faster. I think the main
> reason for the difference is that Bertram's conses much less and
> keeps much less data live on the heap.
>
> I don't find Bertram's version especially hard to read.  I tripped on
> '>>=', but it was easy to look it up.  You can substitute "concatMap"
> without penalty if you hate monads.  The technique used in Bertram's
> `flop' is known to anyone who has been introduced to streams.
>
> I think Bertram solution is an idiomatic "engineered" Haskell program.

Yes, Bertram's is faster. But it's also a lot less readable, IMO. It
uses explicit recursions instead of standard library functions, and
extra complexities here and there. The usage of >>= (and the list
monad) is one example, but have a look at the flop function. I can
only speak for myself but to me that's pretty difficult to understand,
and I really doubt that anyone who hasn't done a significant amount of
Haskell programming will grasp it at all.

So like it says on the wiki, I wrote the most obvious and clear
solution I could come up with, which proved to be several times faster
than the existing Haskell solution in the shootout. I do not claim
that it's the fastest solution possible (in fact, I knew it wasn't)
but it does *no* optimizations that hurt clarity (by design!).

If you think that Bertrams solution is readible then great, then we
have an optimized version that's somewhat readible (personally, I
think it's pretty rough reading, and I can only imagine how a
non-Haskeller would feel). If it turns out that the fastest we comes
up with uses Ptrs and is written entirely in the IO monad, then we're
not so lucky.

/S

--
Sebastian Sylvan
+46(0)736-818655
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