All, I am putting together a halo-exchange benchmark that measures the impact of various strategies including Irecv/Send vs . Irecv/Isend vs use of MPI_datatypes instead of manual pack/unpack. Most importanly, I'd like to measure the impact of using the new MPI_Neighbor_alltoallw. I have a few pieces of working code, but would love to leverage existing work in this area. I get some tantalizing hits on "simple halo exchange program". Does anyone know where I can get the code for "halocompare" Daniel Kokron NASA Ames (ARC-TN) SciCon group 301-286-3959