On 5 December 2016 at 16:49, Massoud Rezavand <msdrezav...@gmail.com> wrote:
> Dear Petsc team, > > In order to create a parallel matrix and solve by KSP, is it possible to > directly use MatSetValues() in runtime when each matrix entry is just > created without MatMPIAIJSetPreallocation()? > Yes, but performance will be terrible without specify any preallocation info. See this note http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatMPIAIJSetPreallocation.html For a code example of for how to do the assembly without preallocation (not recommended), you can refer to this (its the same pattern for MPIAIJ) http://www.mcs.anl.gov/petsc/petsc-current/src/ksp/ksp/examples/tutorials/ex1.c.html > > I mean, when you only know the global size of Mat, and the number of > nonzeros per row is not constant neither for all rows nor during time, is > it possible to set the singular entries into Mat one by one after creating > each one? > Why don't you just destroy the matrix and create a new one every time the non-zero structure changes? That's what I recommended last time. Thanks, Dave > Thanks > Massoud > > > > > > >
