From: "Alain Coetmeur" Newsgroups: comp.parallel.mpi Subject: Re: is it possible to send objects ? Date: Thu, 15 Apr 1999 13:02:05 +0200 Organization: Informatique-CDC Message-Id: <7f4h1o$dk72@puligny.idt.cdc.fr> References: <924170828.773010@www3.netland.nl> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8bit Xref: ukc comp.parallel.mpi:4929 chiwai a écrit dans le message <924170828.773010@www3.netland.nl>... > >Hi thanx for helping me out with the permission denied problem.. it is >finally solved now.. I have an another question can I send objects to an >another process as a derived datatype ? (you mean in C++ ? ) >MPI_Send(object,.......) ? if you create a correct MPI user Type you can ask MPI to transfer a complex structure, but this il restrictued by two facts: 1- your MPI user type be used by the MPI system to read plain data in various place of the structure, but it cannot transfer internal data, identity, which constitute a c++ object. anyway this can be very usefull for an already constructed C++ object that you will fill with the content of a remote one. 2- the MPI type define constant offset from the base pointers, and constant sizes. thus you cannot transmit dynamicaly sized data or data through pointers like we do in C++ for me the second point make MPI_Type unusefull. I've prefered to use MPI_Pack, which is slower (there are copies) but more versatile. however you may design some complex C++ structures so they can be transmited through MPI user type very efficiently. the idea would be to allocate all the C++ data into one new/malloc block, either by making size static or by allocating various objects and arrays at fixed offset in a given block. if the sizing is dynamical you may have to create a MPI_UserType for each size of object and even for every object. be carefull that at the receiving side the sizing must be compatible. in C++ the single block allocation can be acchieved by allocationg a raw memory block (new char or malloc) and using constructor and destructor manually like manual allocator do. there is definetly a place for an Standard Template Library aware extension of MPI so that structures like valarray and vectors are MPI_UserTyped easily. > >is that possible ? > > >My boss has a object oriented program and he wants to know if it is >possible to embed the mpi functions to make it work faster. > >Thanx ! > >