If you are not familiar with the two dimensional heat equation, please have a look for basic description in "Parallel programming with MPI" exercise material.
Here, starting point is a working code parallelized over columns (in Fortran) or rows (in C/C++).
Implement the halo exchange in the exchange() routine in cpp/core.cpp
or fortran/core.F90 with MPI_Neighbor_alltoall. In order to proceed,
you need to have the usage of Cartesian communicator implemented.
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Before start of the communication, the values at the real domain boundaries (i.e not the in the ghost region) need to be copied into a send buffer in the correct order. You may allocate and deallocate the send and receive buffers within the
exchangeroutine, or as recommended as part of the "parallel" data structure. -
Perform the halo exchange with a single call to
MPI_Neighbor_alltoall. -
As the boundary values of neighboring processes are in the receive buffer, values need to be copied to the ghost region.
To build the code, please use the provided Makefile (by typing make). By default, Intel
compiler is used, in order to use gcc type make COMP=gnu.