On Wed, Feb 22, 2023 at 5:45 PM Paul Grosse-Bley <
paul.grosse-b...@ziti.uni-heidelberg.de> wrote:
> I thought to have observed the number of cycles
> with -pc_mg_multiplicative_cycles to be dependent on rtol. But I might have
> seen this with maxits=0 which would explain my missunderstanding of
I thought to have observed the number of cycles withÂ
-pc_mg_multiplicative_cycles to be dependent on rtol. But I might have seen
this with maxits=0 which would explain my missunderstanding of richardson.
I guess PCAMGX does not use this PCApplyRichardson_MG (yet?). Because I still
see the
Preonly means exactly one application of the PC so it will never converge by
itself unless the PC is a full solver.
Note there is a PCApplyRichardson_MG() that gets used automatically with
KSPRICHARSON. This does not have an"extra" application of the preconditioner so
2 iterations of
On Wed, Feb 22, 2023 at 4:57 PM Paul Grosse-Bley <
paul.grosse-b...@ziti.uni-heidelberg.de> wrote:
> Hi again,
>
> I now found out that
>
> 1. preonly ignores -ksp_pc_side right (makes sense, I guess).
> 2. richardson is incompatible with -ksp_pc_side right.
> 3. preonly gives less output for
Hi again,
I now found out that
1. preonly ignores -ksp_pc_side right (makes sense, I guess).
2. richardson is incompatible with -ksp_pc_side right.
3. preonly gives less output for -log_view -pc_mg_log than richardson.
4. preonly also ignores -ksp_rtol etc..
5. preonly causes -log_view to
I was using the Richardson KSP type which I guess has the same behavior as
GMRES here? I got rid of KSPSetComputeInitialGuess completely and will use
preonly from now on, where maxits=1 does what I want it to do.
Even BoomerAMG now shows the "v-cycle signature" I was looking for, so I think
Hi Barry,
the picture keeps getting clearer. I did not use KSPSetInitialGuessNonzero or
the corresponding option, but using KSPSetComputeInitialGuess probably sets it
automatically (without telling one in the output of -help).
I was also confused by the preonly KSP type not working which is
> On Feb 22, 2023, at 2:56 PM, Paul Grosse-Bley
> wrote:
>
> Hi Barry,
>
> I think most of my "weird" observations came from the fact that I looked at
> iterations of KSPSolve where the residual was already converged. PCMG and
> PCGAMG do one V-cycle before even taking a look at the
Hi Barry,
I think most of my "weird" observations came from the fact that I looked at
iterations of KSPSolve where the residual was already converged. PCMG and
PCGAMG do one V-cycle before even taking a look at the residual and then
independent of pc_mg_multiplicative_cycles stop if it is
> On Feb 22, 2023, at 2:19 PM, Paul Grosse-Bley
> wrote:
>
> Hi again,
>
> after checking with -ksp_monitor for PCMG, it seems my assumption that I
> could reset the solution by calling KSPSetComputeInitialGuess and then
> KSPSetupwas generally wrong and BoomerAMG was just the only
Hi again,
after checking with -ksp_monitor for PCMG, it seems my assumption that I could
reset the solution by calling KSPSetComputeInitialGuess and then KSPSetupwas
generally wrong and BoomerAMG was just the only preconditioner that cleverly
stops doing work when the residual is already
> On Feb 22, 2023, at 1:10 PM, Paul Grosse-Bley
> wrote:
>
> Hi Mark,
>
> I use Nvidia Nsight Systems with --trace
> cuda,nvtx,osrt,cublas-verbose,cusparse-verbose together with the NVTX markers
> that come with -log_view. I.e. I get a nice view of all cuBLAS and cuSPARSE
> calls (in
OK, Nsight Systems is a good way to see what is going on.
So all three of your solvers are not traversing the MG hierching with the
correct logic.
I don't know about hypre but PCMG and AMGx are pretty simple and AMGx dives
into the AMGx library directly from out interface.
Some things to try:
*
Hi Mark,
I use Nvidia Nsight Systems with --trace
cuda,nvtx,osrt,cublas-verbose,cusparse-verbose together with the NVTX markers
that come with -log_view. I.e. I get a nice view of all cuBLAS and cuSPARSE
calls (in addition to the actual kernels which are not always easy to
attribute). For
On Wed, Feb 22, 2023 at 11:15 AM Paul Grosse-Bley <
paul.grosse-b...@ziti.uni-heidelberg.de> wrote:
> Hi Barry,
>
> after using VecCUDAGetArray to initialize the RHS, that kernel still gets
> called as part of KSPSolve instead of KSPSetup, but its runtime is way less
> significant than the
On Tue, Feb 7, 2023 at 6:40 AM Matthew Knepley wrote:
> On Tue, Feb 7, 2023 at 6:23 AM Mark Adams wrote:
>
>> I do one complete solve to get everything setup, to be safe.
>>
>> src/ts/tutorials/ex13.c does this and runs multiple solves, if you like
>> but one solve is probably fine.
>>
>
> I
Hi Barry,
after using VecCUDAGetArray to initialize the RHS, that kernel still gets
called as part of KSPSolve instead of KSPSetup, but its runtime is way less
significant than the cudaMemcpy before, so I guess I will leave it like this.
Other than that I kept the code like in my first
On Tue, Feb 7, 2023 at 6:23 AM Mark Adams wrote:
> I do one complete solve to get everything setup, to be safe.
>
> src/ts/tutorials/ex13.c does this and runs multiple solves, if you like
> but one solve is probably fine.
>
I think that is SNES ex13
Matt
> This was designed as a benchmark
I do one complete solve to get everything setup, to be safe.
src/ts/tutorials/ex13.c does this and runs multiple solves, if you like but
one solve is probably fine.
This was designed as a benchmark and is nice because it can do any order FE
solve of Poisson (uses DM/PetscFE, slow).
It should not crash, take a look at the test cases at the bottom of the file.
You are likely correct if the code, unfortunately, does use DMCreateMatrix() it
will not work out of the box for geometric multigrid. So it might be the wrong
example for you.
I don't know what you mean about
Hi Barry,
src/ksp/ksp/tutorials/bench_kspsolve.c is certainly the better starting point,
thank you! Sadly I get a segfault when executing that example with PCMG and
more than one level, i.e. with the minimal args:
$ mpiexec -c 1 ./bench_kspsolve -split_ksp -pc_type mg -pc_mg_levels 2
Paul,
I think src/ksp/ksp/tutorials/benchmark_ksp.c is the code intended to be
used for simple benchmarking.
You can use VecCudaGetArray() to access the GPU memory of the vector and
then call a CUDA kernel to compute the right hand side vector directly on the
GPU.
Barry
> On
Hi,
I want to compare different implementations of multigrid solvers for Nvidia
GPUs using the poisson problem (starting from ksp tutorial example ex45.c).
Therefore I am trying to get runtime results comparable to hpgmg-cuda
(finite-volume), i.e. using multiple warmup and measurement solves
23 matches
Mail list logo
