Re: [Starpu-devel] Data Distribution using Starpumpi

[Samuel Thibault <samuel.thibault@inria.fr>]

Hello,

Yizhou Qian, le sam. 21 déc. 2019 00:28:38 +0800, a ecrit:
>     starpu_mpi_data_register(data1, 0, rank);
>     starpu_mpi_data_register(data2, 1, rank);

You need to say which node really owns the data, i.e.

starpu_mpi_data_register(data1, 0, 0);
starpu_mpi_data_register(data2, 1, 1);

So that in particular rank 1 will know that data1 is on rank 0.

>     if (rank==0) {
>         starpu_mpi_task_insert(MPI_COMM_WORLD,&cl1, STARPU_RW, data1, 0);
>     }
>     else {
>         starpu_mpi_task_insert(MPI_COMM_WORLD,&
> cl2, STARPU_R, data1,STARPU_RW, data2,0);
>     }

Do not put an if here. starpu_mpi_task_insert really inserts the task
only on the MPI node which owns the data. And here rank 0 needs to know
that rank 1 will need the data, so the second starpu_mpi_task_insert
call really needs to be done on rank 0 too, otherwise it will not make
an MPI_Isend.

Samuel