[Haskell-cafe] Why Haskell?
mattcbro at earthlink.net
Sun Jul 23 16:53:25 EDT 2006
David F. Place wrote:
> On Jul 23, 2006, at 1:20 AM, Matthew Bromberg wrote:
>> I do want to understand the advantages of Haskell. My approach has
>> been to consign the heavy imperative, state manipulating code to C
>> and leave the higher end stuff to Haskell. The nature of my
>> problem (a simulation) necessitates holding state for efficiency
>> reasons. (e.g. I don't want to copy a 500 MB matrix every time I
>> change an entry.) I assumed that Haskell would be easier to write
>> and perhaps maintain than the horrors of pure C. At this point
>> there is no turning back. I will probably answer this question soon
> Hi Matthew,
> It seems that a lot of your issues stem from the design decision to
> implement a good chunk of your program in C. There are certainly
> ways to implement an indexed data-structure in Haskell with good
> performance for persistent functional updates. Alternatively, you
> could write imperative code in Haskell to update the array in place
> non-persistently. So, the decision not to use Haskell for that part
> may be a case of premature optimization.
> Cheers, David
> David F. Place
> mailto:d at vidplace.com
> Haskell-Cafe mailing list
> Haskell-Cafe at haskell.org
You make a good point and the decision was by no means cut and dry. However
I made a point of developing some test code using some the newer array data
types and looked at maintaining the array in Haskell and then directly
calling Blas etc. I even had a nice polymorphic matrix class going.
However I found the array interface just a bit too 'clunky' to use a
technical term. The withArray interface is not very appealing. The layers
of lambda notation was giving me a headache.
The idea of separating the imperative code into an imperative language was
appealing to me. Moreover using a stack based architecture for matrix
operations makes the C end of things very easy to implement. The big
bugaboo of memory management issues pretty much disappears, and thinking of
the world state in the IO monad as a stack of matrices has a nice intuitive
appeal for me. It seems to work well so far as I said earlier. I'm not
sure all my issues would have gone away if I had tried to do more of the
matrix op.s in Haskell. It is pretty much a given that I need to interface
to external optimized libraries, that's where the big number crunching is
occuring and those libraries have had teams of Ph.D.s working on them for
years. I want to leverage that. My approach actually minimizes the amount
of marshalling I have to do between C and Haskell. The stack manipulations
are simply scripted in a do clause, with nary an argument being passed.
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