On Fri, Mar 26, 2004 at 01:24:16PM -0000, Simon Marlow wrote:
data PackedString = PS !(ForeignPtr Word8) !Int !Int
A ForeignPtr is a sum type, so it can't be unboxed unfortunately. This is undoubtedly one cause of inefficiency in the code.
Depending on how you're using ForeignPtrs, you could possibly define a specialiased kind of ForeignPtr that would be unboxable. This would require using low-level non-portable stuff though. Are you using mallocForeignPtr? Or adding extra finalizers to ForeignPtrs?
When allocating the ForeignPtr (and not debugging) I use mallocForeignPtrArray without adding extra finalizers. However, I also use ForeignPtr to keep track of mmapped files, in which case I obviously am using munmap (via FFI) as the finalizer and "allocating" using mmap. I think that adding the extra check to see if the pointers are identical sped this up enough that it's probably no longer a major issue--I'm pretty certain that the problem was large strings that were identical, so every byte had to be checked, so probably scary non-portable home-made ForeignPtrs would not be worth the effort. (Although I'm somewhat curious as to how it would be done...) -- David Roundy http://www.abridgegame.org