Re: latest trends in compiler optimization research?

SM Ryan wrote:
> I lost track of Fortran before 90 was standarised, but the array
> notation of 8X was seriously broken: while theoretically letting
> programmers express themselves at a high level, it forced serial
> semantics whether the programmer intended that or no; thus the
> notation could not be vectorised or parallelised any easier than if
> explicit do loops had been used.


The problem with the actual standardized Fortran 90 semantics is
arguably the opposite: it forces parallel semantics whether the
programmer intended that or no. For example,


    a(x) = s * a(y)


(where x and y are vectors) allows x to contain some of the same
elements as y, and requires results that are consistent with calculating
the entire vector of right-hand sides prior to doing any assignments.


This tends, in cases where the scalarizer isn't sufficiently clever (or
sufficiently well-informed), to result in the creation of unnecessary
array temporaries -- which can be a substantial performance hit in cases
where those temporaries are large.


- Brooks


--
The "bmoses-nospam" address is valid; no unmunging needed.

Return to the comp.compilers page.
Search the comp.compilers archives again.