[petsc-users] KSPSolve errors on blues

Fri Jun 10 15:45:21 CDT 2016

On Fri, Jun 10, 2016 at 2:53 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> > On Jun 10, 2016, at 2:04 PM, Xujun Zhao <xzhao99 at gmail.com> wrote:
> >
> > Using gamg makes the convergence super slow (I don't know why)
> >
> > --->test in StokesSolver::solve(): Start the KSP solve...
> >   0 KSP Residual norm 5.077511671295e+01
> >   1 KSP Residual norm 2.902020348172e+01
> >   2 KSP Residual norm 2.034415002085e+01
> >   3 KSP Residual norm 1.525150176412e+01
> >   4 KSP Residual norm 1.332688121023e+01
> >   5 KSP Residual norm 1.178298922349e+01
> >  ..................................
> >  28 KSP Residual norm 1.300489085085e+00
> >  29 KSP Residual norm 1.200176938138e+00
> >  30 KSP Residual norm 1.087425787854e+00
> >
> >
> >
> > In addition, I found the process memory is less than PetscMalloc().
> Should the process memory usage be the PETScMalloc + others?
>
>    Yes, normally process would be more than what was PetscMalloced. The
> case when PetscMalloc is smaller would be when some of the space that was
> PetscMalloced but was never used (say for example I allocate an array with
> 10 million entries but only access the first 100 entries; memory pages are
> created on-demand in unix so no pages would be allocated for most of the
> array hence the process memory would be less than the PetscMalloced memory.)
>
>   So what conclusions did you reach from this
>
> 1)  hypre is using a lot of memory more than GAMG? (only look at process
> memory) Is this confirmed?
>
In this example, yes.

>
> 2) gamg is converging very poorly compared to hypre? This is not good, can
> you run with -fieldsplit_0_ksp_view_mat and send the resulting binary file
> to petsc-maint at mcs.anl.gov so we can see if we can figure out why hypre
> is doing much better than gamg on the matrix.
>
Again yes, only for this specific example and pc setup, especially when
fine mesh is used. Will do.

>
> 3) somewhere in gamg it is allocating much larger memory regions then is
> needed. This is actually not surprising since with sparse matrix algorithms
> such as R A R^T one doesn't know in advance the memory needed and has to
> make upper bound estimates.
>
>    Barry
>
>
>
>
>
>
> > So the former should be more than the later.
> >
> > Summary of Memory Usage in PETSc
> > Maximum (over computational time) process memory:        total
> 1.4316e+10 max 3.7933e+09 min 3.4463e+09
> > Current process memory:                                  total
> 1.4316e+10 max 3.7933e+09 min 3.4463e+09
> > Maximum (over computational time) space PetscMalloc()ed: total
> 6.5987e+10 max 1.7018e+10 min 1.5901e+10
> > Current space PetscMalloc()ed:                           total
> 3.0957e+05 max 7.7392e+04 min 7.7392e+04
> >
> > On Fri, Jun 10, 2016 at 12:07 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> >
> > > On Jun 10, 2016, at 11:43 AM, Xujun Zhao <xzhao99 at gmail.com> wrote:
> > >
> > > I found that this was caused by using -fieldsplit_0_pc_type hypre,
> which ate a lot of memory during the KSPSolve().
> > > Does hypre use BoomerAMG as the default pc type?
> >
> >   Yes
> >
> > > I am curious why it uses such a huge memory. PETSs allocated mem is
> about 22G, but the total process memory is up to 100G. So it looks like the
> additional 70+G is associated with hypre, which is more than 3 times of
> Petsc matrices and vectors!
> >
> >   You can try -fieldsplit_0_pc_type gamg and see how that goes
> memory-wise. The memory used by GAMG will be listed as PETSc allocated
> memory.
> >
> >    Barry
> >
> > >
> > > -Xujun
> > >
> > > On Wed, Jun 8, 2016 at 4:29 PM, Xujun Zhao <xzhao99 at gmail.com> wrote:
> > > OK, this makes sense.
> > > Now my libMesh code use SerialMesh, which keeps a copy on each
> processor, although the operation is parallelized. So it requires more
> memory if multiple CPUs are used. This may be a potential culprit. But I
> suppose the 60x60x60 mesh data(all second order) shouldn't be so large....
> there may be some other bugs
> > >
> > > On Wed, Jun 8, 2016 at 4:18 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > >
> > > > On Jun 8, 2016, at 4:08 PM, Xujun Zhao <xzhao99 at gmail.com> wrote:
> > > >
> > > > Barry,
> > > >
> > > > Thank you. I am testing on the blues.
> > > > btw, what do they mean for the different types of memory usage? for
> example, below is the summary of mem usage for 60x60x60(with 2.9M dofs).
> The max process memory is 3 times as the max space PetscMalloc()ed.
> > >
> > >    PetscMalloced is basically the PETSc data structures; Process
> memory is size of the program plus PETSc malloced space plus space
> allocated by any other library, in this case libMesh. It looks like libMesh
> is requiring a lot of space?
> > >
> > >   Barry
> > >
> > > >
> > > > Summary of Memory Usage in PETSc
> > > > Maximum (over computational time) process memory:        total
> 1.0930e+11 max 5.6928e+10 min 5.2376e+10
> > > > Current process memory:
>        total 3.1762e+09 max 2.8804e+09 min 2.9583e+08
> > > > Maximum (over computational time) space PetscMalloc()ed: total
> 3.0071e+10 max 1.5286e+10 min 1.4785e+10
> > > > Current space PetscMalloc()ed:
>      total 1.5453e+05 max 7.7264e+04 min 7.7264e+04
> > > >
> > > >
> > > >
> > > > On Wed, Jun 8, 2016 at 1:40 PM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > >
> > > > > On Jun 8, 2016, at 1:30 PM, Xujun Zhao <xzhao99 at gmail.com> wrote:
> > > > >
> > > > > A quick test of a smaller system on my laptop with 25x25x25 mesh
> gives the following info.
> > > > > The memory used keeps increasing from 1 to 3 CPUs, but slightly
> decreases with 4 CPUs.
> > > >
> > > >    yes this does not look problematic
> > > >
> > > > > On the other hand, 60x60x60 mesh (2.9M dofs) is also not a big
> system...
> > > >
> > > >   True.
> > > >
> > > >    I think you need to run the 60 60 60 system also on 1 2 4 and 8
> processes to see how the memory trends. I don't think we should eliminate
> memory as the culprit yet.
> > > >
> > > >
> > > >   Barry
> > > >
> > > > >
> > > > >
> > > > > ------------------------------------------------- 1 CPU
> -------------------------------------------------
> > > > > Summary of Memory Usage in PETSc
> > > > > Maximum (over computational time) process memory:        total
> 4.7054e+09 max 4.7054e+09 min 4.7054e+09
> > > > > Current process memory:
>          total 4.7054e+09 max 4.7054e+09 min 4.7054e+09
> > > > > Maximum (over computational time) space PetscMalloc()ed: total
> 1.6151e+09 max 1.6151e+09 min 1.6151e+09
> > > > > Current space PetscMalloc()ed:
>        total 7.7232e+04 max 7.7232e+04 min 7.7232e+04
> > > > >
> > > > > ------------------------------------------------- 2 CPU
> -------------------------------------------------
> > > > > Summary of Memory Usage in PETSc
> > > > > Maximum (over computational time) process memory:        total
> 6.2389e+09 max 3.1275e+09 min 3.1113e+09
> > > > > Current process memory:
>          total 6.2389e+09 max 3.1275e+09 min 3.1113e+09
> > > > > Maximum (over computational time) space PetscMalloc()ed: total
> 2.1589e+09 max 1.1193e+09 min 1.0397e+09
> > > > > Current space PetscMalloc()ed:
>        total 1.5446e+05 max 7.7232e+04 min 7.7232e+04
> > > > >
> > > > > ------------------------------------------------- 3 CPU
> -------------------------------------------------
> > > > > Summary of Memory Usage in PETSc
> > > > > Maximum (over computational time) process memory:        total
> 7.7116e+09 max 1.9572e+09 min 1.8715e+09
> > > > > Current process memory:
>          total 7.7116e+09 max 1.9572e+09 min 1.8715e+09
> > > > > Maximum (over computational time) space PetscMalloc()ed: total
> 2.1754e+09 max 5.8450e+08 min 5.0516e+08
> > > > > Current space PetscMalloc()ed:
>        total 3.0893e+05 max 7.7232e+04 min 7.7232e+04
> > > > >
> > > > > ------------------------------------------------- 4 CPU
> -------------------------------------------------
> > > > > Summary of Memory Usage in PETSc
> > > > > Maximum (over computational time) process memory:        total
> 7.1188e+09 max 2.4651e+09 min 2.2909e+09
> > > > > Current process memory:
>          total 7.1188e+09 max 2.4651e+09 min 2.2909e+09
> > > > > Maximum (over computational time) space PetscMalloc()ed: total
> 2.1750e+09 max 7.6982e+08 min 6.5289e+08
> > > > > Current space PetscMalloc()ed:
>        total 2.3170e+05 max 7.7232e+04 min 7.7232e+04
> > > > >
> > > > >
> > > > > On Wed, Jun 8, 2016 at 11:51 AM, Barry Smith <bsmith at mcs.anl.gov>
> wrote:
> > > > >
> > > > >    Signal 9 SIGKILL on batch systems usually means the process was
> killed because it ran out of time or ran out of memory.
> > > > >
> > > > >     Perhaps there is something in the code that is unscalable and
> requires more more memory with more processes. You can run on 1 2 and 3
> processes and measure the memory usage to see if it goes up with the number
> of processes using for example -memory_view
> > > > >
> > > > >   Barry
> > > > >
> > > > >
> > > > >
> > > > > > On Jun 8, 2016, at 11:41 AM, Xujun Zhao <xzhao99 at gmail.com>
> wrote:
> > > > > >
> > > > > > Hi all,
> > > > > >
> > > > > > I am running a FE Stokes Solver with schur complement type PC on
> blues. The program runs well when mesh is 40X40X40 (0.88M dofs), but when I
> use 60X60X60 mesh, the program crashes and gives out some errors, which
> looks like a segmentation fault. The "strange" thing is that it runs well
> with 1CPU, 2CPUs, but fails on 4 or 8 CPUs. The log files are also
> attached. It seems like the global matrix and vector are assembled well,
> and errors come out before calling the KSPSolve().
> > > > > >
> > > > > > btw, I use the recent PETSc 3.7 dbg version. for libMesh I use
> both dbg and opt version, but none of those can give useful information.
> Has anyone met such situations before? Many thinks.
> > > > > > <ex01_validation_test.o1386940><ex01_validation_test.o1387007>
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> > >
> >
> >
>
>
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