Yet Another Opportunity to Optimize by the Front End.

[Toon Moene]

L.S.,

Last week, when on holiday and really having time to think (as opposed 
to spend my brain cells on office politics), I changed some of our 
Numerical Weather Prediction software (http://hirlam.org) to use a 
linked list of (a derived type consisting of) arrays.

One of the peculiarities of this set up is that the "correct" entry in 
the linked list is found by performing the following test:

       SUBROUTINE AAP(M,N,...,WIM,....)
       ...
       REAL WIM(M,N)
       ...
       IF ( ALL(CURRENT % WIM == WIM) ) THEN
       ...

IOW, the check for matching is ALL("The stored array equals the array 
passed as an argument").

Now this idiom would be greatly sped up if the front end didn't compile 
this the obvious way:

       allocate (temp (m,n))
       loop over n
          loop over m
             temp (...) = x(...) == y(...)
       loop over n
          loop over m
             all = all .and. temp(...)

and evaluated the reduction operator "all" directly into a register.

Is this already considered by some on their to-do list ?

[ The same goes for "any", "sum", etc. ]

Thanks in advance,

-- 
Toon Moene - e-mail: toon@moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
A maintainer of GNU Fortran: http://gcc.gnu.org/fortran/
Who's working on GNU Fortran: 
http://gcc.gnu.org/ml/gcc/2006-01/msg00000.html