Re: [OMPI users] Slow collective MPI File IO

[George Reeke via users]

On Mon, 2020-04-06 at 10:02 -0400, Dong-In Kang via users wrote:
> 
> Thank you Edgar for the information.
> 
> I also tried MPI_File_write_at_all(), but it usually makes the
> performance worse.
> My program is very simple.
> Each MPI process writes a consecutive portion of a file.
> No interleaving among the MPI processes.
> I think in this case I can use MPI_File_write_at().
> 
> 
FWIW, what I do is have each process write its data to node 0 (my term,
I think MPI term is rank 0), and that program does nothing but collect
those messages (using prompts to get them in order without filling all
the buffer space) and write to the file.  I have not timed this vs
other methods, but might be worth a try.
George Reeke