[petsc-dev] Performance of Petsc + ViennaCL 1.5.1 (branch:petsc-dev/next)

[Mani Chandra]

Hi Karl,

I have attached the code already in my last email. It is the last
attachment. The memory leak has been fixed. Thanks!

Cheers,
Mani
On Feb 23, 2014 5:57 AM, "Karl Rupp" <rupp at mcs.anl.gov> wrote:

> Hi Mani,
>
> thanks for the quick feedback.
>
> > I tested the updated implementation of the viennacl bindings in
>
>> petsc-dev/next and I get rather poor performance when using viennacl on
>> either cpu or gpu. I am using the TS module (type:theta) with a simple
>> advection equation in 2D with resolution 256x256 and 8 variables.
>>
>
> Good, this has about 500k unknowns, so OpenCL kernel launch overhead
> should not be a show-stopper.
>
>  I
>> tested with the following cases:
>>
>> 1) Single cpu with petsc's old aij mat and vec implementation
>> 2) Viennacl mat and vec and using VecViennaCLGetArrayRead/Write in the
>> residual evaluation function on an intel cpu with intel's opencl.
>> 3) Viennacl mat and vec and using VecViennaCLGetArrayRead/Write in the
>> residual evaluation function on an nvidia gpu.
>>
>> The first case is the fastest and the other cases are 2-3 times slower.
>> Attached are the log summaries for each cases and the code I used to
>> test with. I am running using the following command:
>>
>> time ./petsc_opencl -ts_monitor -snes_monitor -ts_dt 0.01 -ts_max_steps
>> 10 -ts_type theta -log_summary
>>
>
> As Matt already noted, the bottleneck here is the frequent copy from/to
> the device. I see 90% of the time spent in MatFDColorApply, so this is
> where we need to look at. Is there any chance you can send me the code to
> reproduce this directly? Is it the same you sent me back in January?
>
> Btw: Mani, does the memory still get filled up on the GPU for larger time
> steps?
>
> Best regards,
> Karli
>
>
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