[petsc-dev] http://www.hpcwire.com/hpcwire/2012-11-12/intel_brings_manycore_x86_to_market_with_knights_corner.html

[John R. Cary]

But for FDTD-EM, e.g., we would be doing many tri-diagonal solves at once.  So modulo
memory bandwidth (i.e., small enough problems), AVX should do fine?

Is this the case you are talking about, Paul?

Thx....John

On 11/13/12 11:11 AM, Paul Mullowney wrote:
> Sparse solves. MKL has an option for using multiple CPU cores for their sparse triangular solve with:
>
> mkl_set_num_threads()
>
> Under the hood, the MKL implementation uses the level-scheduler algorithm for extracting some amount of parallelism. We've tested this on many matrices and never seen scalability on a sandy bridge. I don't know the reason for this. For some matrices, the level-scheduler algorithm has a modest amount of parallelism and I would expect some benefit going to multiple cores.
>
> -Paul
>
>
>> On 11/13/12 2:54 AM, Paul Mullowney wrote:
>>> Every test we've done shows that the MKL triangular solve doesn't scale at all on a sandy bridge multi-core. I doubt it will be any different on the Xeon Phi.
>>>
>>> -Paul
>> Do you mean sparse or dense solves? Sparse triangular solves are sequential in MKL. PARDISO also does it sequentially.
>>
>> Anton
>>
>>>>>
>>>>>>
>>>>>> In terms of raw numbers, $2,649 for 320 GB/sec and 8 GB of memory is quite a lot compared to the $500 of a Radeon HD 7970 GHz Edition at 288 GB/sec and 3 GB memory. My hope is that Xeon Phi can do better than GPUs in kernels requiring frequent global synchronizations, e.g. ILU-substitutions.
>>>>>
>>>>>     But, but, but it runs the Intel instruction set, that is clearly worth 5+ times the price :-)
>>>>
>>>> I'm tempted to say 'yes', but at a second thought I'm not so sure whether any of us is actually programming in x86 assembly (again)?
>>>> Part of the GPU/accelerator hype is arguably due to a rediscovery of programming close to hardware, even though it was/is non-x86. With Xeon Phi we might now observe some sort of compiler war instead of low-level kernel tuning - is this what we want?
>>>>
>>>> Best regards,
>>>> Karli
>>>>
>>>
>>>
>