Mark Adams <[email protected]> writes: > I don't need your branch because 1) we are not doing any communication in > this VecAssembly
There is still synchronization cost in determining that nothing needs to be done. Moreover, using a size P MPI_Allreduce for that (in PetscMaxSum) is non-scalable. My branch uses MPI_Reduce_scatter_block (scalable) when available (MPI-2.2). > and I added the IGNORE stuff So it takes no time now and everything is groovy?
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