[mpiwg-rma] RMA WG Telecon

Joseph Schuchart schuchart at hlrs.de
Wed Sep 12 03:26:32 CDT 2018


I listened in for the MPI-RMA WG telco yesterday and found some 
interesting points in it. In particular, I am interested in the 
discussion on atomics and same_op. I support the notion that MPI should 
choose a conservative default to make sure users do not run into 
surprising UB because the implementation expects or supports only 
same_op, which the user may not be aware of.

As a developer of a framework built on top of MPI RMA I would also be 
interested in getting information from the MPI implementation on which 
atomic operations are actually supported in hardware on the current 
system, which would allow me to pick different implementations of a 
specific feature to fully exploit the available hardware capabilities 
(similar to C++ `std::atomic_is_lock_free`). Are there any plans to 
provide such an interface? This could be used in combination with an 
info key (say `native_op`) that promises that the user will only use a 
mix of operations that are supported in hardware, which would then avoid 
the required fall-back to active messages discussed yesterday.

Last but not least, I am also interested in the shared memory 
optimization for collectives (iirc, MPI_DISCARD?). I couldn't find an 
issue on Github on this. Is there any publicly available information you 
can share?

Any input would be much appreciated.

Many thanks in advance,

On 09/10/2018 09:21 PM, Balaji, Pavan via mpiwg-rma wrote:
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