boost::mpi::scatterv and boost::mpi::gatherv added

[Júlio Hoffimann <julio.hoffimann@…>]

Two more collective operations for Boost.MPI. I made the headers completely based on the existent one: scatter.hpp and gather.hpp

"common use versions" was added too, for those cases where the great buffer is stored contiguously at the root process.

The "common use version" of gatherv needs a warning in the docs: Since the process send it's own buffer size and nothing more, all sizes will be gathered before the real call. I don't know if this is tolerable, you have the decision.

Other doubt about gatherv implementation: I did switch to the packed_archive_send() / packed_archive_recv() communication, i tried to figure out the difference in send an archive or send using communicator::send when dealing with non-MPI types, but without success. boost::mpi::scatter uses the first and boost::mpi::gather uses the second. Anyway,the snippet of code is commented if you want to switch back.

I'm sending a Main.cpp file with the simple tests i made, comment or uncomment the prototypes in pairs: scatterv / gatherv.

To see the results in a separate terminal for each process, this is a possible way:

mpicxx Main.cpp -o test && echo 107 > input.txt && mpirun -np 4 xterm -e ./test

[Júlio Hoffimann <julio.hoffimann@…>]

Fixed version

[Júlio Hoffimann <julio.hoffimann@…>]

Fixed version

[Júlio Hoffimann <julio.hoffimann@…>]

Fixed version

[Júlio Hoffimann <julio.hoffimann@…>]

Fixed version 2

[Júlio Hoffimann <julio.hoffimann@…>]

Fixed version 3

[Júlio Hoffimann <julio.hoffimann@…>]

Fixed version 2

[Júlio Hoffimann <julio.hoffimann@…>]

Thinking better... the gatherv prototype that calls gather is not great. Was discarded and the user needs to pass all sizes.

[Júlio Hoffimann <julio.hoffimann@…>]

I don't understand so much about copyright terms, be free to remove my name in the header files. :-)

Júlio.

[dkushner2@…]

Can we receive an update on this, please? Seems like an excellent and much-needed addition to the present implementation. As it stands, the Boost implementation of scatter is all but useless (i.e. no support for count-array and thus no ability to scatter a vector that is greater than the comm size).