Hi,
In general, even in your serial fortran code, you're already taking a performance hit using a derived type.
That is not generally true. The right statement is: "it depends".Yes, sometimes derived data types and object orientation and so on can lead to some performance hit; but current compiler usually can oprimise alot.
E.g. consider http://www.terboven.com/download/OAbstractionsLA.pdf (especially p.19).
So, I would not recommend to disturb the ready program in order to let it be the old good f77 style. And let us not start a flame about "assembler is faster but OO is easier"! :-)
Best wishes Paul
-----Original Message----- From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org] On Behalf Of Prentice Bisbal Sent: Wednesday, May 05, 2010 11:51 AM To: Open MPI Users Subject: Re: [OMPI users] Fortran derived types Vedran Coralic wrote:Hello, In my Fortran 90 code I use several custom defined derived types.Amongst them is a vector of arrays, i.e. v(:)%f(:,:,:). I am wondering what the proper way of sending this data structure from one processor to another is. Is the best way to just restructure the data by copying it into a vector and sending that or is there a simpler way possible by defining an MPI derived type that can handle it?I looked into the latter myself but so far, I have only found the solution for a scalar fortran derived type and the methodology that was suggested in that case did not seem naturally extensible to the vector case.It depends on how your data is distributed in memory. If the arrays are evenly distributed, like what would happen in a multidimensional-array, the derived datatypes will work fine. If you can't guarantee the spacing between the arrays that make up the vector, then using MPI_Pack/MPI_Unpack (or whatever the Fortran equivalents are) is the best way to go. I'm not an expert MPI programmer, but I wrote a small program earlier this year that created a dynamically created array of dynamically created arrays. After doing some research into this same problem, it looked like packing/unpacking was the only way to go. Using Pack/Unpack is easy, but there is a performance hit since the data needs to be copied into the packed buffer before sending, and then copied out of the buffer after the receive. -- Prentice _______________________________________________ users mailing list us...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/users _______________________________________________ users mailing list us...@open-mpi.org http://www.open-mpi.org/mailman/listinfo.cgi/users
-- Dipl.-Inform. Paul Kapinos - High Performance Computing, RWTH Aachen University, Center for Computing and Communication Seffenter Weg 23, D 52074 Aachen (Germany) Tel: +49 241/80-24915
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