Re: [eigen] patch to add ACML support to BTL

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

Hi,

just to say I updated the main benchmark page.

Gael

On Tue, Mar 17, 2009 at 10:27 AM, Rohit Garg <rpg.314@xxxxxxxxx> wrote:
> Thanks for that. After looking at these benches, I was thinking that
> perhaps Eigen has become quite slower with new versions!!
>
> On Tue, Mar 17, 2009 at 2:52 PM, Gael Guennebaud
> <gael.guennebaud@xxxxxxxxx> wrote:
>> On Tue, Mar 17, 2009 at 9:20 AM, Rohit Garg <rpg.314@xxxxxxxxx> wrote:
>>> I think that with new library versions, new eigen versions, and new
>>> gcc we should put these results on the main benchmark page of eigen
>>> website. BTW I think the eigen's performance has slipped considerably
>>> when I look at your Pentium D benchmarks, or it's all attributable to
>>> core2 being a much better cpu?
>>
>> thanks for the benchs,
>>
>> core2 is indeed much better than a Pentium D, and since I only have a
>> core2, the critical parts (matrix-matrix products) are only fine tuned
>> for the core2. Another reason is that gcc 4.3 generates slower code
>> than 4.2: some constant expressions are not removed out the inner
>> loops, it is not optimal with block expressions, and by default 4.3
>> automatically generates vectorized code which conflicts with Eigen's
>> automatic vectorization. 4.4 do not suffer from all these issues, and
>> sometimes, gcc 4.4 auto-vec is even better than Eigen's explicit one
>> because it better understands what it is doing: an example is rank-2
>> update which simply consists in a series "v += ax + by" ops. But
>> Eigen's explicit vec is still worth it because we are able to
>> vectorize much more cases than gcc. Examples: "v = ax + by" is not
>> vectorized by gcc, matrix products, vectorization + explicit
>> unrolling, in the future sin, cos, pow, exp, etc.
>>
>> gael
>>
>>> On Tue, Mar 17, 2009 at 1:08 PM, Victor <flyaway1212@xxxxxxxxx> wrote:
>>>> Hi all.
>>>> It sure took a while to run all the benchmarks with all the libraries
>>>> available to me... I wish I had read the instructions more carefully and
>>>> hadn't wasted any time testing multithreaded libraries...
>>>> Anyways, the results are on the wiki:
>>>> http://eigen.tuxfamily.org/index.php?title=Benchmark_AMD_Intel_compare
>>>>
>>>> Gael Guennebaud wrote:
>>>>>
>>>>> Hi Victor,
>>>>>
>>>>> thanks a lot for the patch.
>>>>> applied in rev 935462, the syr2 header will follow in a second.
>>>>>
>>>>> so what's your conclusion, is ACML as good as MKL ?
>>>> Unfortunately, no. ACML is not bad though. It's hard to say once and for
>>>> all, but most of the time MKL beats ACML. Even on an AMD CPU MKL is
>>>> typically better. ACML shows decent performance (even on Intel CPU), on
>>>> average similar to ATLAS, but again results differ from test to test.
>>>> The good thing about ACML (and MKL, Goto and ATLAS) is that they can be
>>>> used in multithreading mode, which unfortunately can't be demonstrated
>>>> with BTL as far as I can tell.
>>>>
>>>> Also, it looks like in comparison with other libs Eigen does better on
>>>> Intel than on AMD.
>>>>
>>>> Out of curiosity, I have also run BTL with Eigen compiled with 4
>>>> different compilers. Well, 3 different gcc versions and intel c++. See
>>>> the results here
>>>> http://eigen.tuxfamily.org/index.php?title=Eigen2_benchmark_Intel
>>>>
>>>> I hope this might be useful to somebody.
>>>>
>>>> Cheers,
>>>> Victor.
>>>>
>>>
>>>
>>>
>>> --
>>> Rohit Garg
>>>
>>> http://rpg-314.blogspot.com/
>>>
>>> Senior Undergraduate
>>> Department of Physics
>>> Indian Institute of Technology
>>> Bombay
>>>
>>>
>>>
>>
>>
>>
>
>
>
> --
> Rohit Garg
>
> http://rpg-314.blogspot.com/
>
> Senior Undergraduate
> Department of Physics
> Indian Institute of Technology
> Bombay
>
>
>