[Haskell-cafe] Analyzing slow performance of a Haskell program

[Chris Yuen]

Here is an updated version using Data.Array.Unboxed  http://ideone.com/YXuVL
And the profile http://hpaste.org/49940

Still taking 5+ minutes...

Chris

On Sun, Aug 7, 2011 at 5:20 PM, Daniel Fischer <
daniel.is.fischer at googlemail.com> wrote:

> On Sunday 07 August 2011, 10:52:20, Max Bolingbroke wrote:
> > In short I don't see how to get further without changing the algorithm
> > or doing some hacks like manual unrolling. Maybe someone else has some
> > ideas?
>
> Well, the C# implementation uses arrays for lookup while the Haskell
> version uses list lookups
>
>                      in (tens !! fromIntegral t) ++ wordify x
>
> and case'd functions
>
> lenTens 0 = 0
> lenTens 1 = 3
> lenTens 2 = 6
> lenTens 3 = 6
> lenTens 4 = 5
> lenTens 5 = 5
> lenTens 6 = 5
> lenTens 7 = 7
> lenTens 8 = 6
> lenTens 9 = 6
>
> wordify is only called once at the end, so that should not have a
> measurable impact, but the lenXXXs might.
> I'm not sure what
>
> CaseLen.$wlenTens :: GHC.Prim.Int# -> GHC.Prim.Int#
> [GblId,
>  Arity=1,
>  Str=DmdType L,
>  Unf=Unf{Src=<vanilla>, TopLvl=True, Arity=1, Value=True,
>         ConLike=True, Cheap=True, Expandable=True,
>         Guidance=IF_ARGS [12] 11 0}]
> CaseLen.$wlenTens =
>  \ (ww_shY :: GHC.Prim.Int#) ->
>    case ww_shY of _ {
>      __DEFAULT ->
>        CaseLen.lenTens1
>        `cast` (CoUnsafe GHC.Types.Int GHC.Prim.Int#
>                :: GHC.Types.Int ~ GHC.Prim.Int#);
>      0 -> 0;
>      1 -> 3;
>      2 -> 6;
>      3 -> 6;
>      4 -> 5;
>      5 -> 5;
>      6 -> 5;
>      7 -> 7;
>      8 -> 6;
>      9 -> 6
>    }
>
> means at a lower level, but it's certainly worth trying out whether an
> unboxed array lookup is faster.
>
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