Hi Lux, You can still use MPI send/receive or MPI RMA with datatypes to exchange the halo region in a shared window, similar to the flat-MPI version. But I think you might want to completely avoid extra copies for intra-node neighbors when using shared window. I.e., instead of copying the edge elements to neighbors' halo, a process can directly read the edge elements owned by a neighbor if it is in the same shared window. Thus, you use MPI communication with datatypes only for neighbors who are on remote node. Min On 2018/05/10 12:00, Luis Cebamanos wrote:

Hi Min,

Thanks for your help. My intention is to use shared mem windows in a 3D halo exchange communication. The application already uses complex MPI datatypes for the exchange of edges and corners. I guess my question is how should I deal with this? Should I manually unpack the MPI datatypes into a shared memory buffer, then communicate (intra- and inter- node) and finally pack the data back to its original data structure so the simulation can carry on with other operations.

double *baseptr; MPI_Win_allocate_shared (len, 1, MPI_INFO_NULL, mpi3->shmcomm,                                          &baseptr, &mpi3->win);

Pointer baseptr gives me the address to the shared mem window, but I cannot see the way of using datatypes in the shared mem created.

Thanks Lux

On 10/05/2018 16:53, Min Si wrote:

...

Hi Lux,

Yes, you can use MPI datatype with shared window. Can you provide more information about the purpose to use shared window thus we can give appropriate suggestion ?

Best regards, Min

On 2018/05/10 10:05, Luis Cebamanos wrote:

...

Hi all,

Is there a way to deal with MPI datatypes when using shmm windows? What is the advice to convert a flat MPI code that uses MPI datatypes for halo exchanges to use shmm windows?

Thanks! Lux

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