Giuseppe,
We totally rewrote the GPU matrix-free framework on the latest release of
deal.II (version 9.5). One of the advantages is that you can now
write/debug the code on the CPU and then switch to run the code on the GPU.
The new code is not 100% backward compatible but the changes are pretty
small. I advise you to switch to the latest version of deal.II, debug the
code on the CPU, and then run on the GPU.
Best,
Bruno
Le lun. 17 juil. 2023 à 14:12, giuseppe orlando <giusor...@gmail.com> a
écrit :
> Dear Bruno,
> thank you very much. That was the issue with the matrix-based version.
> I take the opportunity for another question (sorry in advance to bother).
> I also tried to implement a matrix-free version of the same problem,
> exploiting therefore all the routines such as 'assemble_rhs' and delegating
> the action of the matrix to suitable operators. The results are the same
> for a few time-steps and then it blows up. I guess that it is something
> again related to the memory access, but I couldn't figure out the issue. In
> thics case, it should not be CUDA::Handle, because I am not using it since
> we are in a matrix-free framework.
>
> Thanks again for the previous suggestion.
>
> Best,
>
> Giuseppe
>
> Il giorno lunedì 17 luglio 2023 alle 17:50:27 UTC+2 bruno.t...@gmail.com
> ha scritto:
>
>> Giuseppe,
>>
>> The CUDA::Handle needs to live longer than the sparse matrix but in your
>> code it goes out-of-scope at the end of assemble_system(). I know the same
>> code works with assemble_matrix but it only works "by chance" because
>> nothing wrote over the memory. I don't know if that's the only problem but
>> that's definitely wrong.
>>
>> Best,
>>
>> Bruno
>>
>> Le lun. 17 juil. 2023 à 11:06, giuseppe orlando <gius...@gmail.com> a
>> écrit :
>>
>>> Here, you can find the two codes. 'SBR_GPU' is the one that arrives up
>>> to the end, whereas 'SBR_GPU_WRONG' is the one that stops with the error
>>> described above once I call 'output_results'. If the code is too long and
>>> can be helpful, I could try to reduce it avoiding ParameterHandler and
>>> other more 'advanced' stuff and to reduce everything to a unique file.
>>>
>>> Best,
>>>
>>> Giuseppe
>>>
>>> Il giorno lunedì 17 luglio 2023 alle 16:11:18 UTC+2 bruno.t...@gmail.com
>>> ha scritto:
>>>
>>>> Giuseppe,
>>>>
>>>> It's hard to tell what's wrong without seeing the code.
>>>>
>>>> Best,
>>>>
>>>> Bruno
>>>>
>>>> On Monday, July 17, 2023 at 9:04:42 AM UTC-4 gius...@gmail.com wrote:
>>>>
>>>>> Hello everyone,
>>>>> I'm writing this post to ask some help for a CUDA code. I have
>>>>> implemented a matrix-based CUDA coda for the so-called solid body
>>>>> rotation,
>>>>> namely a time dependent advection problem. In my first implementation, I
>>>>> encapulased the computation of the matrix and of the right-hand side of
>>>>> the
>>>>> resulting linear system in the same routine ('assemble_system'). Then, I
>>>>> tried to separate the assembling of the matrix ('assemble_matrix') and of
>>>>> the rhs ('assemble_rhs'). Since the matrix does not change (I am using an
>>>>> explicit time integration scheme and, therefore, the resulting matrix is a
>>>>> mass matrix), I compute it at the beginning and then I just update the
>>>>> right-hand side. Everything works until I save the results, after which I
>>>>> obtain this error ("On entry to cusparseSpMV() parameter number 1 (handle)
>>>>> had an illegal value: invalid pointer mode").
>>>>> I also tried to create an auxiliary vector just for saving, but
>>>>> nothing changes.
>>>>> Everything runs with 1 GPU. Have anyone ever obtained this kind of
>>>>> issue? If it can help, I can share the two versions of the code.
>>>>>
>>>>> Thanks in advance
>>>>>
>>>>> Best
>>>>>
>>>>> Giuseppe
>>>>>
>>>> --
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