Re: [eigen] a record for Eigen: 250 GFLOPS !!

[Gael Guennebaud <gael.guennebaud@xxxxxxxxx>]

On Wed, Jun 23, 2010 at 6:12 PM, Manoj Rajagopalan <rmanoj@xxxxxxxxx> wrote:
>
> Congrats! :-)
>
> Quick question: in GEMM benchmarks, does one FLOP represent a * followed by a
> +, or does it mean just one of these. In the latter case, the FLOPS figure
> would be ~ (2-eps) times that from the former.

"one FLOP" == "one *" or "one +"

there is no "eps", the factor is a pure 2 because we are doing C += A * B;

gael

>
> thanks,
> Manoj
>
>
>
> On Wednesday 23 June 2010 06:04:58 am Gael Guennebaud wrote:
>> Hi,
>>
>> this morning I played with a 48 cores AMD SMP server (8 processors
>> AMD-Opteron-8439-SE, 6 cores each @ 2,8 GHz) and a bi-processor made
>> of Intel X5570 @ 2.93GHz (4 multithreaded cores each => a total of 8
>> cores, 16 threads), and here are the results for a product of 2048^2
>> matrices of floats:
>>
>> ** Intel **
>>
>> 16 threads (multi-threading)
>> eigen real        0.158446s     108.427 GFLOPS  (2.22212s)
>> mt speed up x5.55349 => 34.7093%
>>
>> 8 threads
>> eigen real        0.125598s     136.785 GFLOPS  (1.2581s)
>> mt speed up x7.0835 => 88.5438%
>>
>> 4 threads
>> eigen real        0.228977s     75.0287 GFLOPS  (2.37034s)
>> mt speed up x3.88544 => 97.136%
>>
>> 2 threads
>> eigen real        0.449604s     38.2111 GFLOPS  (4.72754s)
>> mt speed up x1.98317 => 99.1583%
>>
>> 1 thread
>> eigen mono cpu    0.891639s     19.2677 GFLOPS  (8.9178s)
>>
>>
>> a speed up factor of ~7 for 8 cores is a very nice scaling IMO.
>>
>>
>> ** AMD **
>>
>>
>> 1 thread
>> eigen mono cpu    1.54084s      11.1496 GFLOPS  (15.4136s)
>>
>> 2 threads
>> eigen real        0.817967s     21.0031 GFLOPS  (8.18607s)
>> mt speed up x1.88375 => 94.1874%
>>
>> 4 threads
>> eigen real        0.41879s      41.0226 GFLOPS  (4.1911s)
>> mt speed up x3.73174 => 93.2936%
>>
>> 8 threads
>> eigen real        0.214083s     80.2485 GFLOPS  (2.15697s)
>> mt speed up x7.49282 => 93.6602%
>>
>> 16 threads
>> eigen real        0.115521s     148.716 GFLOPS  (1.26385s)
>> mt speed up x13.4568 => 84.1048%
>>
>> 24 threads
>> eigen real        0.168208s     102.135 GFLOPS  (1.75357s)
>> mt speed up x9.55177 => 39.7991%
>>
>> 32 threads
>> eigen real        0.0686023s    250.427 GFLOPS  (1.19708s)
>> mt speed up x23.001 => 71.8781%
>>
>> 42 threads
>> eigen real        0.0799503s    214.882 GFLOPS  (0.938163s)
>> mt speed up x19.9015 => 47.3844%
>>
>> 48 threads
>> eigen real        0.143299s     119.888 GFLOPS  (1.62653s)
>> mt speed up x11.2097 => 23.3536%
>>
>>
>> We can see that AMD's SSE implementation is half the speed of Intel's
>> one. This architecture seems to be tricky to control because the peak
>> performance is obtained with 32 threads with a speed up factor of x23
>> that is not bad. With more threads the perf significantly drops down.
>> There is also a slow down with 24 threads.
>>
>> that's all folks.
>>
>> gael
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