Re: JIT - automated mexing

[David Bateman]

Fotios Kasolis wrote:
> On Jun 24, 2010, at 9:46 PM, David Bateman wrote:
>
>   
> > Fotios Kasolis wrote:
> >     
> > > Is there someone that is planing to introduce (or already implementing) JIT in 
> > > Octave? If not, i ll place that on my MOST_DESIRED list. Unfortunately i do not 
> > > have the knowledge (yet) to do it but i ll start working on that whenever i 
> > > find some time (any help: links, books, whatever ;D).
> > >
> > > An idea (which i do not know if implementable but sounds so)
> > > Instead of a traditional JIT what about automated mexing? Sth like
> > >
> > >  
> > >       
> > > > mex_my_loops(myfunc)
> > > >    
> > > >         
> > > will replace all (replaceable) loops by mexed ones? Does this sound reasonable 
> > > (if not why?)? At least it sounds relatively easier than JIT and more user 
> > > oriented (it is always good to have a choice)
> > >
> > > /Fotios
> > >
> > >  
> > >       
> > I think JIT is a lot harder than you think. There is no strict variable typing 
> > in Octave and so you need to discover what types are used before you can call 
> > the appropriate compiled functions. Also variable types can be polymorphic. 
> > Consider something like
> >
> > a = 1
> > for i = 0:.1:2
> > a += asin(i);
> > endfor
> >
> > Yes I know its an artifical example, but consider what happens to the type of a 
> > when i=1.1.... There is a JIT in FreeMat but FreeMat essentially got rid of 
> > there logical and single precision types to simplify the detection of code 
> > where the JIT compiler might be applied.
> >
> > I'd suggest you look at the JIT code in FreeMat in any case for inspiration, at
> >
> > http://freemat.svn.sourceforge.net/viewvc/freemat/branches/ArraySimplification/libs/libMatC/
> >
> > Regards
> > David
> >
> >     
>
> I think of JIT as hard as it is but no more than that! But what about  the 
> automated mex code solution?
>
> /Fotios
>   
What is automatic mexing but a use of a piece of compiled code in a 
JIT.. I don't really see the distinction. The hard bits are still the 
same (variable type discover, loop optimisation, etc).. Lucky LLVM does 
a lot  of this stuff already

D.


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