On Tue, Jan 22, 2019 at 1:35 PM Matthew Knepley <[email protected]<mailto:[email protected]>> wrote: On Tue, Jan 22, 2019 at 2:23 PM Zhang, Junchao via petsc-dev <[email protected]<mailto:[email protected]>> wrote: 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. I think you might want this: https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PetscSF/PetscSFFetchAndOpBegin.html I read it as: Leaves are accumulated to root (root is changed), and leaves get a snapshot of the root before each atomic update. It is not what I want. Thanks, Matt --Junchao Zhang -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/<http://www.cse.buffalo.edu/~knepley/>
