[petsc-dev] How to add root values to leaves in PetscSF?

[Zhang, Junchao]

I want to add root values to leaves, and keep root unchanged. PetscSFBcast came to my mind, but unfortunately it only broadcasts roots and does not have an MPI_Op argument like PetscSFReduce for me to choose from INSERT_VALUES, ADD_VALUES, etc.
Any tips? Thanks.

PS: I met this problem when I tried to implement VecScatter in SF.  In VecScatter, multiple entries of vec x can be scattered to the same entry of vec y, and one entry of x can also be scattered to multiple entries of y.  I want to use one SF for all combinations of SCATTER_FORWARD/BACKWARD, INSERT/ADD_VALUES. It seems impossible with current SF interface.
--Junchao Zhang
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