Its purpose is to preallocate off-diagonal blocks, but unless you're hard up against your memory capacity, I would skip that clumsy code and use MatPreallocator.
"Ellen M. Price via petsc-users" <[email protected]> writes: > Hello again! > > For my multiphysics problem, I think a DMComposite might make the most > sense, since some variables are only defined in 1d (so any 2d > information is just wasting memory and CPU), while others have a full 2d > distribution. To tell PETSc how the two DMs should be coupled, it looks > like I need DMCompositeSetCoupling, but there are no examples on how to > use it, or even what the parameters of the provided function mean. Does > anyone have a simple example to share? Doesn't have to be full code, a > snippet would be just fine. > > Thanks, > Ellen Price
