[Haskell-beginners] Functional Data Structure with Cheapest Modification?

[Edward Z. Yang]

Excerpts from Travis Erdman's message of Tue Apr 06 15:31:30 -0400 2010:
> In my application, I have a collection of (only) about 200 objects.  So from
> the surface, not large at all.  However, each object in the collection is a
> large tree that might be up to 20 MB in size.  The application pulls objects
> one at a time from the collection, performs some processing, and delivers a
> new, updated object that needs to be inserted in the collection for future
> processing (the original object is now obsolete).  I'm guessing a Data.IntMap
> might involve copying over about 8 objects for each single object update,
> which while better than copying all 200, is still not perfect.

The construction of Haskell tree types is such that the tree is automatically
storing pointers to the actual object: it's only if you ask that the value
be unboxed explicitly that it gets stored with the node.  So you're only paying
for a few pointer copies, not a huge 20MB copy.

Have you profiled your application and found this to be the bottleneck?

Cheers,
Edward