[Libmesh-users] Assemble matrices without initializing equation system?

[David X. <dx...@my...>]

Hi All,

I was trying to assemble the stiffness and mass matrices on a dense mesh
with 531441 nodes (40x40x40, HEX27, 3rd, HERMITE) and I ran into "Out of
memory" problem at the line of:

equation_systems.init();


Here's the error message:

[0]PETSC ERROR: PetscMallocAlign() line 62 in src/sys/memory/mal.c
[0]PETSC ERROR: Out of memory. This could be due to allocating
[0]PETSC ERROR: too large an object or bleeding by not properly
[0]PETSC ERROR: destroying unneeded objects.
[0]PETSC ERROR: Memory allocated 1380430780 Memory used by process 886095872
[0]PETSC ERROR: Try running with -malloc_dump or -malloc_log for info.
[0]PETSC ERROR: Memory requested 907039528!
[0]PETSC ERROR: PetscTrMallocDefault() line 191 in src/sys/memory/mtr.c
[0]PETSC ERROR: MatSeqAIJSetPreallocation_SeqAIJ() line 2735 in
src/mat/impls/aij/seq/aij.c
[0]PETSC ERROR: MatCreateSeqAIJ() line 2621 in src/mat/impls/aij/seq/aij.c
[0]PETSC ERROR: User provided function() line 137 in
unknowndirectory/src/numerics/petsc_matrix.C
[unset]: aborting job:
application called MPI_Abort(comm=0x84000000, 1) - process 0

My question is: is it possible to assemble the matrices without having to
initilize the equation system? My goal is just to output the assembled
system matrices to files and i don't have to solve them inside libmesh.

Thanks!

David