[Bug c++/35117] Vectorization on power PC

["victork at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #28 from victork at gcc dot gnu dot org  2008-02-11 14:21 -------
>   As for the last email, Victor:
>   1. Using a smaller number of iterations, doesnt help me. This is not what the
> real world code runs.

Looks like in your example the memory subsystem is a performance bottleneck.
Vectorization alone does not help. Probably you need to think how to partition
your arrays to fit the data cache.

>   2. new/malloc almost didnt do anything maybe a gain of 20%

With data allocated my malloc compiler is able to prove independence
statically. So, it would be better to alocate memory by malloc.

>   3. The difference between 1.738sec and 0.781sec can either be a 2 times
> performance gain or simply a 1 second gain that would remain 1 second for more
> intensive calculations. Therefore I cant use/rely on the test you did.

See an example in my previous comment. It is about 2.4 times performance gain.
-- Victor


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35117