dons:
sedillard:
Hi,
I've got a library that I'm in the process of uploading to hackage (waiting for account) but the darcs repo is here:
[1]http://graphics.cs.ucdavis.edu/~sdillard/Vec
I notice a slight drop in performance when I install the library using cabal. Maybe 10-20%, on one particular function. This is in comparison to when the library is 'local', as in, the source files are in the same directory as the client application.
Lack of unfolding and inlining when compiled in a package? Try compiling with -O2, for maximum unfolding.
What could be causing the performance drop? The function in question requires impractical amounts of inlining (This is something of an experiment), but I don't see how installing it as a library affects that. The functions to be inlined are small, surely available in the .hi files.
You can check this via -show-iface
Its only when they are applied do they agglomerate into a big mess - 80-200K lines of core.
The function in question is invertMany in examples/Examples.hs.
Some general remarks, GHC isn't (yet) a whole program compiler by default. So it doesn't, by default, inling entire packages across package boundaries. So you can lose some specialisation/inlining, sometimes, by breaking things across module boundaries. That said, it's entirely possible to program libraries in a way to specifically allow full inlining of the libraries. The Data.Binary and Data.Array.Vector libraries are written in this style for example, which means lots of {-# INLINE #-} pragmas, maximum unfolding and high optimisation levels. -- Don