On 20:39 Fri 11 Apr , Jeff Squyres wrote: > Also, it's been a long time since I've done anything serious in C++, > but are you guaranteed that &foo[x] for a vector<> will yield > contiguous memory?
Good question. I was used to believe so, but I just had a look at the standard and couldn't find any guarantee on that subject... However, if your implementation doesn't work that way, you're pretty much screwed, as the vector's interface makes it hard to detect non-contiguous blocks. > You might be better off using the Boost C++ MPI bindings; they provide > all kinds of nifty things for classes, etc. True, but sometimes this convenience comes at a cost: "When communicating data types over MPI that are not fundamental to MPI (such as strings, lists, and user-defined data types), Boost.MPI must first serialize these data types into a buffer and then communicate them; the receiver then copies the results into a buffer before deserializing into an object on the other end. For some data types, this overhead can be eliminated by using is_mpi_datatype. However, variable-length data types such as strings and lists cannot be MPI data types." [1] AFAIK, boost::mpi will thus buffer all vectors to be sent. This might not be as efficient as just feeding it a raw pointer and the number of elements. Cheers! -Andreas [1] http://www.boost.org/doc/libs/1_35_0/doc/html/mpi/tutorial.html#mpi.point_to_point -- ============================================ Andreas Schäfer Cluster and Metacomputing Working Group Friedrich-Schiller-Universität Jena, Germany PGP/GPG key via keyserver I'm a bright... http://www.the-brights.net ============================================ (\___/) (+'.'+) (")_(") This is Bunny. Copy and paste Bunny into your signature to help him gain world domination!
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