[petsc-dev] SetPreallocationCSR

[Smith, Barry F.]

   It is an oversight. It saves a global reduction in the MatAssembly since all the processes know they don't need to communicate anything.

   Barry

> On Aug 24, 2019, at 7:55 AM, Pierre Jolivet via petsc-dev <petsc-dev at mcs.anl.gov> wrote:
> 
> Hello,
> Out of the three SetPreallocationCSR implementations (for MPIAIJ, MPIBAIJ, and MPISBAIJ), only MPIAIJ is forcing MAT_NO_OFF_PROC_ENTRIES to PETSC_TRUE before the final AssemblyBegin/AssemblyEnd:
> - AIJ https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/aij/mpi/mpiaij.c.html#line3957
> - BAIJ https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/baij/mpi/mpibaij.c.html#line2782 and SBAIJ https://www.mcs.anl.gov/petsc/petsc-current/src/mat/impls/sbaij/mpi/mpisbaij.c.html#line2262
> 
> Is this option not relevant for those two types or is this an oversight?
> 
> Thanks,
> Pierre