Please find inline comments.
On Fri, Aug 22, 2014 at 3:45 PM, Rob Latham <r...@mcs.anl.gov> wrote: > > > On 08/22/2014 02:40 PM, Saliya Ekanayake wrote: > >> Yes, these are all MPI_DOUBLE >> > > well, yeah, but since you are talking about copying into a "direct buffer" > there must be something tricker about the layout than just N*M doubles. > > sometimes people allocate 2d arrays by allocating one array of N elements, > then allocating and storing an array of length M in each of the N slots. > Yes, the computation part of the program stores these values as an array of arrays (N elements each pointing to an array of M elements). > > (you can find a dozen of these types of questions on stackoverflow, for > example) > > if the java interface allows you to describe with an MPI Datatype, or if > you were working in C or Fortran, you can construct an HINDEXED type (or > with very new MPICH, HINDEXED_BLOCK) and send that instead of copying. > I think this would work only if we have all M*N values allocated continuously. Thank you, Saliya > > ==rob > > >> >> On Fri, Aug 22, 2014 at 3:38 PM, Rob Latham <r...@mcs.anl.gov >> <mailto:r...@mcs.anl.gov>> wrote: >> >> >> >> On 08/22/2014 10:10 AM, Saliya Ekanayake wrote: >> >> Hi, >> >> I've a quick question about the usage of Java binding. >> >> Say there's a 2 dimensional double array (size m x n) that needs >> to be >> sent to another rank. I see two options to get this done, >> >> 1. Copy values to a direct buffer of size m*n and send it >> 2. Copy values to a 1D array of size m*n and send it >> >> >> i have no idea about the java mpi bindings, but can you describe the >> type with an mpi datatype? >> >> ==rob >> >> >> I guess 2 would internally do the copying to a buffer and use it, >> so >> suggesting 1. is the best option. Is this the case or is there a >> better >> way to do this? >> >> >> Thank you, >> Saliya >> -- >> Saliya Ekanayake esal...@gmail.com <mailto:esal...@gmail.com> >> <mailto:esal...@gmail.com <mailto:esal...@gmail.com>> >> >> http://saliya.org >> >> >> _________________________________________________ >> >> users mailing list >> us...@open-mpi.org <mailto:us...@open-mpi.org> >> Subscription: >> http://www.open-mpi.org/__mailman/listinfo.cgi/users >> >> <http://www.open-mpi.org/mailman/listinfo.cgi/users> >> Link to this post: >> http://www.open-mpi.org/__community/lists/users/2014/08/ >> __25130.php >> >> <http://www.open-mpi.org/community/lists/users/2014/08/25130.php> >> >> >> -- >> Rob Latham >> Mathematics and Computer Science Division >> Argonne National Lab, IL USA >> >> _________________________________________________ >> >> users mailing list >> us...@open-mpi.org <mailto:us...@open-mpi.org> >> Subscription: http://www.open-mpi.org/__mailman/listinfo.cgi/users >> >> <http://www.open-mpi.org/mailman/listinfo.cgi/users> >> Link to this post: >> http://www.open-mpi.org/__community/lists/users/2014/08/__25135.php >> <http://www.open-mpi.org/community/lists/users/2014/08/25135.php> >> >> >> >> >> -- >> Saliya Ekanayake esal...@gmail.com <mailto:esal...@gmail.com> >> >> Cell 812-391-4914 Home 812-961-6383 >> http://saliya.org >> >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users >> Link to this post: http://www.open-mpi.org/community/lists/users/2014/08/ >> 25136.php >> >> > -- > Rob Latham > Mathematics and Computer Science Division > Argonne National Lab, IL USA > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: http://www.open-mpi.org/community/lists/users/2014/08/ > 25137.php > -- Saliya Ekanayake esal...@gmail.com Cell 812-391-4914 Home 812-961-6383 http://saliya.org
