From t.dt.aanderson at [hidden] Thu Nov 10 07:01:42 2011 From: t.dt.aanderson at [hidden] (Thomas Anderson) Date: Thu, 10 Nov 2011 21:01:42 +0800 Subject: [Mpi-22] Datatype questions Message-ID: I read the mpi document (http://www.mpi-forum.org/docs/mpi-2.2/mpi22-report.pdf) where it states that a filetype is either a single etype or a derived MPI datatype constructed from multiple instances of the same etype. This looks like the definition only allow one datatype as elementary type. However, when looking some examples such as struct (http://www.osc.edu/supercomputing/training/mpi/Feb_05_2008/mpi_0802_mod_datatypes.pdf), it allows several datatypes passed in to construct a new datatype. In this example (struct), how can a user determine which datatype is the elementary type? Or in fact a filetype can contains multiple elementary types. In addition, is derived datatype can only constructed by routines (mpi_type_contiguous, mpi_type_vector, etc.)? Can a programmer compose derived datatype from predefined mpi datatype (such as mpi_int + mpi_float)? Thanks.