Hello. I was trying to use MPI_Neighbor_alltoallw() and was following the example on page 333 of the MPI-3.0 standard. However I believe the send and receive counts are incorrect. Lines 21 to 25: DO i=1,num_neigh sndcounts(i) = 100 rcvcounts(i) = 100 rcvtypes(i) = sndtypes(i) END DO Since the send/receive counts for 1 and 2 are vectors types of length 100, we should be sending/receiving only 1 type/element. As follows: sndcounts(1) = 1 sndcounts(2) = 1 sndcounts(3) = 100 sndcounts(4) = 100 rcvcounts = sndcounts Indeed if I compile the example as per the standard, I get data corruption. I couldn't find this in the errata published on May 14, 2014. However if it is a known mistake please ignore my comment. Regards Timothy Brown