[MLton-user] defunctorize limit?

[Matthew Fluet]

On Mon, 10 Dec 2007, Sean McLaughlin wrote:
> I'm experiencing some unexpected behavior.  I have a number of
> functors parameterized by
> an abstract arithmetic signature.  For most of my code, when these
> functors are instantiated to
> Real.real type, they run as fast as a version without the abstraction.
> However, I found an
> example that runs over 10X slower with the abstraction than without.
> That is, when I
> inline a monomorphic function at type real, it runs 10X faster than
> when I instantiate
> a functor with the exact same function body.  So far I have been
> unable to construct
> a small example that exhibits this behavior.  I was thus wondering if
> there is a limit
> to the amount of defunctorization being done.  If so, perhaps there is
> a command line
> argument I could increase.

There is no limit to defunctorization; all functor bodies are 
duplicated at every functor application site.  I don't see anything 
obvious from your code fragment that would explain the behavior you are 
seeing.  It should be the case that a functor application is equivalent to 
copying the body of the functor to that point.  Feel free to post code 
demonstrating the behavior to:
   http://mlton.org/TemporaryUpload

One thing that can happen when you manually duplicate code is that you 
introduce identical functions that are inlined independently.