[petsc-users] Multiple solves with PCMG fail
Mark Adams
mfadams at lbl.gov
Tue Oct 21 17:53:05 CDT 2014
I am getting this in the output:
[0] VecNormalize(): Vector of zero norm can not be normalized; Returning
only the zero norm
[0] KSPGMRESCycle(): Converged due to zero residual norm on entry
[0]PETSC ERROR: KSPComputeEigenvalues() line 119 in
/Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c Null Pointer:
Parameter # 3
[0]PETSC ERROR: PETSC: Attaching /usr/bin/gdb to ./test1 of pid 50632 on
display /tmp/launch-ikNsM1/org.macosforge.xquartz:0 on machine
Macintosh-6.local
and in gdb I see this (appended). The problem is that
KSPComputeEigenvalues is called with NULL outputs. This because
KSPChebyshevComputeExtremeEigenvalues_Private get the number of iterations
and it is zero, it mallocs zero, and this is an error.
Should there be a check like:
326 ierr = KSPGetIterationNumber(kspest,&n);CHKERRQ(ierr);
if (!n) bail out
327 ierr = PetscMalloc2(n,&re,n,&im);CHKERRQ(ierr);
or is something going wrong upstream?
Mark
#5 0x000000010fb86057 in PetscAttachDebuggerErrorHandler (comm=1140850689,
line=119, fun=0x1115b0a25 "KSPComputeEigenvalues", file=0x1115b09b9
"/Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c", num=85,
p=PETSC_ERROR_INITIAL, mess=0x7fff50102290 "Null Pointer: Parameter # 3",
ctx=0x0) at /Users/markadams/Codes/petsc/src/sys/error/adebug.c:462
#6 0x000000010fb88d30 in PetscError (comm=1140850689, line=119,
func=0x1115b0a25 "KSPComputeEigenvalues", file=0x1115b09b9
"/Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c", n=85,
p=PETSC_ERROR_INITIAL, mess=0x1115518ca "Null Pointer: Parameter # %d") at
/Users/markadams/Codes/petsc/src/sys/error/err.c:378
#7 0x0000000110bd3464 in KSPComputeEigenvalues (ksp=0x7fe92d813e60, n=0,
r=0x0, c=0x0, neig=0x7fff50102c14) at
/Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c:119
#8 0x0000000110b6a915 in KSPChebyshevComputeExtremeEigenvalues_Private
(kspest=0x7fe92d813e60, emin=0x7fff50102ca0, emax=0x7fff50102ca8) at
/Users/markadams/Codes/petsc/src/ksp/ksp/impls/cheby/cheby.c:328
#9 0x0000000110b69043 in KSPSolve_Chebyshev (ksp=0x7fe92c869a60) at
/Users/markadams/Codes/petsc/src/ksp/ksp/impls/cheby/cheby.c:373
#10 0x0000000110bd81ce in KSPSolve (ksp=0x7fe92c869a60, b=0x7fe92d002860,
x=0x7fe92d007c60) at
/Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c:460
#11 0x0000000110a8e4b8 in PCMGMCycle_Private (pc=0x7fe92c862e60,
mglevelsin=0x7fe92c868a60, reason=0x0) at
/Users/markadams/Codes/petsc/src/ksp/pc/impls/mg/mg.c:19
#12 0x0000000110a9e1d5 in PCApply_MG (pc=0x7fe92c862e60, b=0x7fe92d002860,
x=0x7fe92d007c60) at
/Users/markadams/Codes/petsc/src/ksp/pc/impls/mg/mg.c:337
#13 0x0000000110ad6f2c in PCApply (pc=0x7fe92c862e60, x=0x7fe92d002860,
y=0x7fe92d007c60) at
/Users/markadams/Codes/petsc/src/ksp/pc/interface/precon.c:440
#14 0x0000000110affbd2 in KSP_PCApply (ksp=0x7fe92c833a60,
x=0x7fe92d002860, y=0x7fe92d007c60) at kspimpl.h:230
#15 0x0000000110afcd31 in KSPSolve_CG (ksp=0x7fe92c833a60) at
/Users/markadams/Codes/petsc/src/ksp/ksp/impls/cg/cg.c:139
#16 0x0000000110bd81ce in KSPSolve (ksp=0x7fe92c833a60, b=0x0, x=0x0) at
/Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c:460
#17 0x000000010fafea7d in main ()
(gdb) frame 8
#8 0x0000000110b6a915 in KSPChebyshevComputeExtremeEigenvalues_Private
(kspest=0x7fe92d813e60, emin=0x7fff50102ca0, emax=0x7fff50102ca8) at
/Users/markadams/Codes/petsc/src/ksp/ksp/impls/cheby/cheby.c:328
328 ierr = KSPComputeEigenvalues(kspest,n,re,im,&neig);CHKERRQ(ierr);
Current language: auto; currently minimal
(gdb) p re
$1 = (PetscReal *) 0x0
(gdb) list
323 PetscReal *re,*im,min,max;
324
325 PetscFunctionBegin;
326 ierr = KSPGetIterationNumber(kspest,&n);CHKERRQ(ierr);
327 ierr = PetscMalloc2(n,&re,n,&im);CHKERRQ(ierr);
328 ierr = KSPComputeEigenvalues(kspest,n,re,im,&neig);CHKERRQ(ierr);
329 min = PETSC_MAX_REAL;
330 max = PETSC_MIN_REAL;
331 for (n=0; n<neig; n++) {
332 min = PetscMin(min,re[n]);
On Tue, Oct 21, 2014 at 6:29 PM, Mark Adams <mfadams at lbl.gov> wrote:
> Humm, GAMG works fine form (like you said), but with MG (with or without
> Galerkin) on 1 or 4 procs I get:
>
> [0]PETSC ERROR: KSPComputeEigenvalues() line 119 in
> /Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c Null Pointer:
> Parameter # 3
>
> Can you tell me exactly what you get with:
>
> ./test1 -pc_type mg
>
> I get:
>
> [0]PETSC ERROR: KSPComputeEigenvalues() line 119 in
> /Users/markadams/Codes/petsc/src/ksp/ksp/interface/itfunc.c Null Pointer:
> Parameter # 3
> [0]PETSC ERROR: PETSC: Attaching /usr/bin/gdb to ./test1 of pid 50433 on
> display /tmp/launch-ikNsM1/org.macosforge.xquartz:0 on machine
> Macintosh-6.local
>
> And, it seems that the RHS is all zeros on one processor.
>
> I am using a debug build. Try to do the same.
>
>
>
>
> On Tue, Oct 21, 2014 at 2:50 AM, Filippo Leonardi <
> filippo.leonardi at sam.math.ethz.ch> wrote:
>
>> Here,
>>
>> run this e.g. with
>> mpirun -np 4 ./test1 -draw_pause -1 -pc_type mg -pc_mg_galerkin
>>
>> In Debug mode it crashes, in standard mode it fails. Using Petsc current.
>>
>> Run without mg and works!
>>
>> Hope it's not me being stupid and doing something terribly wrong!
>>
>> Best,
>> Filippo
>>
>> On Monday 20 October 2014 07:29:04 Barry Smith wrote:
>> > Can you send us the code: to petsc-maint at mcs.anl.gov or
>> > petsc-users at mcs.anl.gov ? Or something that reproduces the problem?
>> >
>> > Barry
>> >
>> > > On Oct 20, 2014, at 3:31 AM, Filippo Leonardi
>> > > <filippo.leonardi at sam.math.ethz.ch> wrote:
>> > >
>> > > Hi,
>> > >
>> > > I have a very specific problem that I cannot figure out with PCMG and
>> > > multiple solves. I got a linear system that I solve many times, with
>> same
>> > > matrix but different RHS. I can successfully solve the system with
>> > > standard techniques, such as default solver or LU or PCGAMG. Even MG
>> > > works if I destroy the ksp each time or I recompute the matrices at
>> each
>> > > time. But when I try and go to MG and not recomputing the matrices
>> each
>> > > time the solver fails. Any idea?
>> > >
>> > > Here some detail: the setup:
>> > > ierr = KSPSetDMActive(ksp, PETSC_FALSE); CHKERRQ(ierr);
>> > > ierr = KSPSetDM(ksp, da); CHKERRQ(ierr);
>> > > ierr = KSPSetComputeOperators(ksp, ComputeMatrix, ctx); CHKERRQ(ierr);
>> > > ierr = KSPSetComputeRHS(ksp, ComputeRHS, ctx); CHKERRQ(ierr);
>> > > ierr = KSPSetFromOptions(ksp); CHKERRQ(ierr);
>> > >
>> > > Then I solve as usual, for a large number of time steps:
>> > > ierr = KSPSolve(ksp, NULL, NULL); CHKERRQ(ierr);
>> > > ierr = KSPGetSolution(ksp, &phi);
>> > >
>> > > The solver converges and does that in a reasonable number of
>> iterations:
>> > > Linear solve converged due to CONVERGED_RTOL iterations 7
>> > > And ksp_view and ksp_monitor do not show any weird stuff.
>> > >
>> > > - Weirdly enough using any solver (for instance cg+bjacobi or gamg)
>> > > everything works (So the matrix and RHS are working fine).
>> > > - But the problem persists with Galerkin matrices (-pc_mg_galerkin)
>> (So is
>> > > not a ComputeMatrix problem).
>> > > - If I do:
>> > > ierr = KSPSetComputeOperators(ksp, ComputeMatrix, this);
>> CHKERRQ(ierr);
>> > > between each solve or destroy the ksp entirely each time the solution
>> is
>> > > also perfect (So is not a boundary scaling or other stuff problem).
>> > > - If I run MG with only 2 levels (so just coarse) I also get a fine
>> > > result.
>> > >
>> > > Setup RHS is called each time as expected, setup matrix is called just
>> > > once, also as expected.
>> > >
>> > > The only thing I can think is that MG does not update some value that
>> > > actually needs to be recomputed.
>> > >
>> > > Any idea?
>> > >
>> > > The solution is not that different from:
>> > >
>> http://www.mcs.anl.gov/petsc/petsc-current/src/ksp/ksp/examples/tutorials/
>> > > ex29.c.html
>> > >
>> > > Best,
>> > > Filippo
>>
>
>
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