Hi All, I ran into a problem with MPI_SCATTERV. When the sendcounts (scounts in code) is the same for every process, it works fine, but if the sendcounts is different (e.g., 1, 2, 3, 4 for 4 processes, respectively), there will be error as follows: Fatal error in PMPI_Scatterv: Message truncated, error stack: PMPI_Scatterv(376)................: MPI_Scatterv(sbuf=0000000000000000, scnts=0000000000E16CD0, displs=0000000000E16CA0, MPI_INT, rbuf=0000000002BD0050, rcount=1, MPI_INT, root=0, MPI_COMM_WORLD) failed MPIR_Scatterv_impl(187)...........: MPIR_Scatterv(144)................: MPIDI_CH3U_Receive_data_found(129): Message from rank 0 and tag 6 truncated; 16 bytes received but buffer size is 4 The code is simple as follows: call MPI_SCATTERV(ja_in, *scounts*, displs, MPI_INT, ja, *scounts*, MPI_INT, 0, comm , ierr) ja_in is allocated for process #0 and ja is allocated for every process. The size of ja_in and ja is big enough to hold large dataset. Thanks and regards, Danyang