Re: C++ Expression Template Benchmarks for GCC/Clang/Intel/PGI/MSVC

[Walter Landry <wlandry at caltech dot edu>]

Richard Guenther <richard.guenther@gmail.com> wrote:
> On Fri, Jun 15, 2012 at 12:54 AM, Walter Landry <wlandry@caltech.edu> wrote:
>> Hello Everyone,
>>
>> I thought you might be interested in some C++ expression template
>> benchmarks I have done.
>>
>> ?http://www.wlandry.net/Projects/FTensor#Benchmarks
>>
>> I found that GCC optimized the expression template code better than
>> unrolling expressions by hand. ?In fact, GCC was far, far better at
>> optimizing code with expression templates than any other compiler. ?I
>> ran the same benchmarks back in 2003, and GCC has improved quite a lot
>> since then.
> 
> Heh, yeah - quite possibly because I myself was working with a POOMA
> based CFD code during my PhD which made me start working on inproving
> GCC for expression template code ;)  It is btw interesting to try to enable
> profile-feedback for the compilers - for some compilers you'll see that
> the profile-generating executables are so slow as to be unusable (as they
> seem to keep all calls of the expression templates).

I got around to trying profile guided optimization.  For GCC it did
not make much difference, but for Intel it made a huge improvement for
the expression template code.  Of course, the training executable ran
20 times slower.  But that was better than the Open64 compiler which
was too slow for me to get results.  I have added a section on PGO.

  http://www.wlandry.net/Projects/FTensor#PGO

I also added results from Open64 and Pathscale's ENZO.

Cheers,
Walter Landry
wlandry@caltech.edu