Confused by profiling

Ian Lynagh
Fri, 14 Sep 2001 17:18:14 +0100

On Fri, Sep 14, 2001 at 04:53:27PM +0100, Simon Marlow wrote:
> >      p_aexp_list         Parser           0    0.0   0.0      
> >       con2tag_Token#     Tokens         880    0.0   0.0      
> >       pIfThing           PC_base        896    0.0   0.0      
> > 
> > Now basically my problem is how things under p_aexp_list can 
> > be entered
> > 896 times if p_aexp_list is entered 0 times - am I reading it wrong?
> Hmmm.  I suspect it may be to do with the fact that p_aexp_list isn't a
> function, it's a CAF (constant applicative form - basically a top-level
> expression).  The "entries" field counts the number of times an SCC
> annotation is executed, which corresponds more to "calls" than entries.
> I must admit I haven't thought too hard about this.
> It might be helpful to see what happens to the code inside the compiler:

OK, I think I see why the output being generated is what it is. However,
it doesn't actually seem very useful to me.

> Perhaps the act of appending an SCC annotation when entering a  function
> closure should bump the entry counts for all the cost centres  in the
> stack.  That might yield more reasonable-looking figures.

If that means what I think it might mean then I agree, but I don't get
the "in the stack" bit.