[petsc-users] Weak scaling test with geometric multigrid

[Smith, Barry F.]

   DMDA requires that there be at least 1 grid points in each direction on each process (this simplified the implementation a huge amount but gives up flexibility). In your case you have 16 processes in a particular direction but a total of only 12 grid points hence not enough grid points to have at least 1 per process.

  Barry


> On Jan 10, 2018, at 5:25 AM, Buesing, Henrik <hbuesing at eonerc.rwth-aachen.de> wrote:
> 
> Dear all, 
>  
> I am doing a weak scaling test using geometric multigrid. With increasing the number of cells, and the number of processes, I also increase the number of multigrid levels. With 64 cores, 12288 cells in x-direction and 11 multigrid levels, I see error message [1]. 
>  
> Could you help me understand what is happening here?
>  
> The characteristics of the weak scaling test are summarized in table [2]. Refinement level 7-9 went through fine.
>  
> Thank you!
> Henrik
>  
> [1]
>  
> [0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
> [0]PETSC ERROR: Argument out of range
> [0]PETSC ERROR: Partition in x direction is too fine! 12 16
> [0]PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for trouble shooting.
> [0]PETSC ERROR: Petsc Development GIT revision: v3.8.2-48-g851ec02  GIT Date: 2017-12-05 09:52:17 -0600
> [0]PETSC ERROR: shem_fw64gnu_const.x on a gnu_openmpi named linuxihfc033.rz.RWTH-Aachen.DE by hb111949 Wed Jan 10 11:48:09 2018
> [0]PETSC ERROR: Configure options --download-fblaslapack --with-cc=mpicc -with-fc=mpif90 --with-cxx=mpicxx --download-hypre --download-superlu_dist --download-suitesparse --download-scalapack --download-blacs --download-hdf5 --download-parmetis --download-metis --with-debugging=0 --download-mumps
> [0]PETSC ERROR: #1 DMSetUp_DA_3D() line 299 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/impls/da/da3.c
> [0]PETSC ERROR: #2 DMSetUp_DA() line 25 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/impls/da/dareg.c
> [0]PETSC ERROR: #3 DMSetUp() line 720 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/interface/dm.c
> [0]PETSC ERROR: #4 DMCoarsen_DA() line 1203 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/impls/da/da.c
> [0]PETSC ERROR: #5 DMCoarsen() line 2427 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/dm/interface/dm.c
> [0]PETSC ERROR: #6 PCSetUp_MG() line 618 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/ksp/pc/impls/mg/mg.c
> [0]PETSC ERROR: #7 PCSetUp() line 924 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/ksp/pc/interface/precon.c
> [0]PETSC ERROR: #8 KSPSetUp() line 381 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: #9 KSPSolve() line 612 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/ksp/ksp/interface/itfunc.c
> [0]PETSC ERROR: #10 SNESSolve_NEWTONLS() line 224 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/snes/impls/ls/ls.c
> [0]PETSC ERROR: #11 SNESSolve() line 4179 in /rwthfs/rz/cluster/work/hb111949/Code/petsc/src/snes/interface/snes.c
>  
>  
> [2]
>  
> # refinement level
> # cores
> # cells in x
> # cells in y
> # cells in z
> # mg levels
> 7
> 1
> 1536
> 1
> 256
> 8
> 8
> 4
> 3072
> 1
> 512
> 9
> 9
> 16
> 6144
> 1
> 1024
> 10
> 10
> 64
> 12288
> 1
> 2048
> 11
>  
> --
> Dipl.-Math. Henrik Büsing
> Institute for Applied Geophysics and Geothermal Energy
> E.ON Energy Research Center
> RWTH Aachen University
> ------------------------------------------------------
> Mathieustr. 10            |    Tel +49 (0)241 80 49907
> 52074 Aachen, Germany     |    Fax +49 (0)241 80 49889
> ------------------------------------------------------
> http://www.eonerc.rwth-aachen.de/GGE
> hbuesing at eonerc.rwth-aachen.de
> ------------------------------------------------------