[petsc-users] Eisenstat-Walker method with GPU assembled matrices

[Matthew Knepley]

On Tue, Oct 20, 2020 at 4:40 AM Héctor Barreiro Cabrera <hecbarcab at gmail.com>
wrote:

> El jue., 15 oct. 2020 a las 23:32, Barry Smith (<bsmith at petsc.dev>)
> escribió:
>
>>
>>   We still have the assumption the AIJ matrix always has a copy on the
>> GPU.  How did you fill up the matrix on the GPU while not having its copy
>> on the CPU?
>>
>> My strategy here was to initialize the structure on the CPU with dummy
> values to have the corresponding device arrays allocated. Ideally I would
> have initialized the structure on a kernel as well, since my intention is
> to keep all data on the GPU (and not hit host memory other than for
> debugging). But since the topology of my problem remains constant over
> time, this approach proved to be sufficient. I did not find any problem
> with my use case so far.
>
> One thing I couldn't figure out, though, is how to force PETSc to transfer
> the data back to host. MatView always displays the dummy values I used for
> initialization. Is there a function to do this?
>

Hmm, this should happen automatically, so we have missed something. How do
you change the values on the device?

  Thanks,

    Matt


> Thanks for the replies, by the way! I'm quite surprised how responsive the
> PETSc community is! :)
>
> Cheers,
> Héctor
>
>
>>   Barry
>>
>>   When we remove this assumption we have to add a bunch more code for CPU
>> only things to make sure they properly get the data from the GPU.
>>
>>
>> On Oct 15, 2020, at 4:16 AM, Héctor Barreiro Cabrera <hecbarcab at gmail.com>
>> wrote:
>>
>> Hello fellow PETSc users,
>>
>> Following up my previous email
>> <https://lists.mcs.anl.gov/pipermail/petsc-users/2020-September/042511.html>,
>> I managed to feed the entry data to a SeqAICUSPARSE matrix through a CUDA
>> kernel using the new MatCUSPARSEGetDeviceMatWrite function (thanks Barry
>> Smith and Mark Adams!). However, I am now facing problems when trying to
>> use this matrix within a SNES solver with the Eisenstat-Walker method
>> enabled.
>>
>> According to PETSc's error log, the preconditioner is failing to invert
>> the matrix diagonal. Specifically it says that:
>> [0]PETSC ERROR: Arguments are incompatible
>> [0]PETSC ERROR: Zero diagonal on row 0
>> [0]PETSC ERROR: Configure options PETSC_ARCH=win64_vs2019_release
>> --with-cc="win32fe cl" --with-cxx="win32fe cl" --with-clanguage=C++
>> --with-fc=0 --with-mpi=0 --with-cuda=1 --with-cudac="win32fe nvcc"
>> --with-cuda-dir=~/cuda --download-f2cblaslapack=1 --with-precision=single
>> --with-64-bit-indices=0 --with-single-library=1 --with-endian=little
>> --with-debugging=0 --with-x=0 --with-windows-graphics=0
>> --with-shared-libraries=1 --CUDAOPTFLAGS=-O2
>>
>> The stack trace leads to the diagonal inversion routine:
>> [0]PETSC ERROR: #1 MatInvertDiagonal_SeqAIJ() line 1913 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\mat\impls\aij\seq\aij.c
>> [0]PETSC ERROR: #2 MatSOR_SeqAIJ() line 1944 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\mat\impls\aij\seq\aij.c
>> [0]PETSC ERROR: #3 MatSOR() line 4005 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\mat\INTERF~1\matrix.c
>> [0]PETSC ERROR: #4 PCPreSolve_Eisenstat() line 79 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\ksp\pc\impls\eisens\eisen.c
>> [0]PETSC ERROR: #5 PCPreSolve() line 1549 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\ksp\pc\INTERF~1\precon.c
>> [0]PETSC ERROR: #6 KSPSolve_Private() line 686 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\ksp\ksp\INTERF~1\itfunc.c
>> [0]PETSC ERROR: #7 KSPSolve() line 889 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\ksp\ksp\INTERF~1\itfunc.c
>> [0]PETSC ERROR: #8 SNESSolve_NEWTONLS() line 225 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\snes\impls\ls\ls.c
>> [0]PETSC ERROR: #9 SNESSolve() line 4567 in
>> C:\cygwin64\home\HBARRE~1\PETSC-~1\src\snes\INTERF~1\snes.c
>>
>> I am 100% positive that the diagonal does not contain a zero entry, so my
>> suspicions are either that this operation is not supported on the GPU at
>> all (MatInvertDiagonal_SeqAIJ seems to access host-side memory) or that I
>> am missing some setting to make this work on the GPU. Is this correct?
>>
>> Thanks!
>>
>> Cheers,
>> Héctor
>>
>>
>>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20201020/26c03436/attachment.html>