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 enough.
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@vidplace.com
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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. -- View this message in context: http://www.nabble.com/Why-Haskell--tf1986013.html#a5458965 Sent from the Haskell - Haskell-Cafe forum at Nabble.com.