bug ? number of processor, coarse and fine DA for DMMG

[nicolas aunai]

Hello,


I have a code that uses the DMMG objet for a linear problem. The DA I
create for the coarse grid is DA_XPERIODIC and 2D. I let petsc decide
for the number of processors in each direction.

I have a problem which depends on the number of processors I use.
If I want a 1024x1025 grid with 4 levels, the coarsest grid will be
128x129 with the default refinement factor.

Everything seems to work fine when I run with 1, 2, 3, 4, 6, 8...
processors... but 5, 7, 11 proc fail with the following error :


nicolas at lx-nau:~/code/tests/petsc/dmmg$ mpiexec -n 5 ./inertia6
-ksp_type gmres -pc_type sor -ksp_rtol 1e-9

size of the coarse level : 128 129
debug 1, number of proc in each dir. : 1 5

[3]PETSC ERROR: --------------------- Error Message
------------------------------------
[3]PETSC ERROR: Arguments are incompatible!
[3]PETSC ERROR: Processor's coarse DA must lie over fine DA
    j_start 615 j_c 307 j_start_ghost_c 308!
[3]PETSC ERROR:
------------------------------------------------------------------------
[3]PETSC ERROR: Petsc Release Version 3.0.0, Patch 7, Mon Jul  6
11:33:34 CDT 2009
[3]PETSC ERROR: See docs/changes/index.html for recent updates.
[3]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
[3]PETSC ERROR: See docs/index.html for manual pages.
[3]PETSC ERROR:
------------------------------------------------------------------------
[3]PETSC ERROR: ./inertia6 on a linux-gnu named lx-nau by nicolas Fri
Sep  4 14:39:27 2009
[3]PETSC ERROR: Libraries linked from
/home/nicolas/bin/petsc-3.0.0-p7/linux-gnu-debug/lib
[3]PETSC ERROR: Configure run at Mon Aug 17 11:34:27 2009
[3]PETSC ERROR: Configure options --with-cc=gcc --with-fc=gfortran
--download-f-blas-lapack=1 --download-mpich=1
PETSC_ARCH=linux-gnu-debug --with-shared=0
[3]PETSC ERROR:
------------------------------------------------------------------------
[3]PETSC ERROR: DAGetInterpolation_2D_Q1() line 280 in src/dm/da/src/dainterp.c
[3]PETSC ERROR: DAGetInterpolation() line 879 in src/dm/da/src/dainterp.c
[3]PETSC ERROR: DMGetInterpolation() line 144 in src/dm/da/utils/dm.c
[3]PETSC ERROR: DMMGSetDM() line 309 in src/snes/utils/damg.c



it seems that the error come from the routine DMMGSetDM, when petsc
build the restriction/interpolation operators... but I can't figure
out why I couln't use 5 processors with this grid size ?

if the code is needed, it is here : http://nico.aunai.free.fr/inertia6.c


Thx for your help

Nico