I think, technically, copy-in/out might occur on the subroutine boundary in this case. This is one of the big problems, especially for the nonblocking calls like MPI_Isend/Irecv. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Iain Bason Sent: Thursday, September 18, 2008 7:28 PM To: MPI-3 Fortran working group Subject: [MPI3 Fortran] Non-contiguous arrays (was Re: Argument data sizes) On Sep 18, 2008, at 1:13 PM, Jeff Squyres wrote:

How else would you do it efficiently for non-contiguous datatypes without a copy (which would be quite Bad for multiple reasons, especially for very large datasets)? Such issues are certainly not unique to C (even in very large Fortran arrays, particularly if you want to send just a plane from the middle of a 3D array, or somesuch). As another example of where datatypes are useful: with the Fortran equivalent of C structs, you need to build up a composed datatype to describe the message that you want to send/receive.

Didn't this come up in another thread? In Fortran, you can use assumed shape arrays to pass these sorts of data without copying. It would be nice if MPI could take advantage of that in order to make life easier for Fortran programmers. Iain _______________________________________________ mpi3-fortran mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-fortran --------------------------------------------------------------------- Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen Germany Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer Registergericht: Muenchen HRB 47456 Ust.-IdNr. VAT Registration No.: DE129385895 Citibank Frankfurt (BLZ 502 109 00) 600119052 This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies.