Claire,
> Is it possible to use the one-sided communication without combining
it with synchronization calls?
What exactly do you mean by "synchronization calls"? MPI_Win_fence is
indeed synchronizing (basically flush+barrier) but MPI_Win_lock (and the
passive target synchronization interface at large) is not. It does incur
some overhead because the lock has to be taken somehow at some point.
However, it does not require a matching call at the target to complete.
You can lock a window using a (shared or exclusive) lock, initiate RMA
operations, flush them to wait for their completion, and initiate the
next set of RMA operations to flush later. None of these calls are
synchronizing. You will have to perform your own synchronization at some
point though to make sure processes read consistent data.
HTH!
Joseph
On 4/24/20 5:34 PM, Claire Cashmore via users wrote:
Hello
I was wondering if someone could help me with a question.
When using RMA is there a requirement to use some type of
synchronization? When using one-sided communication such as MPI_Get the
code will only run when I combine it with MPI_Win_fence or
MPI_Win_lock/unlock. I do not want to use MPI_Win_fence as I’m using the
one-sided communication to allow some communication when processes are
not synchronised, so this defeats the point. I could use
MPI_Win_lock/unlock, however someone I’ve spoken to has said that I
should be able to use RMA without any synchronization calls, if so then
I would prefer to do this to reduce any overheads using MPI_Win_lock
every time I use the one-sided communication may produce.
Is it possible to use the one-sided communication without combining it
with synchronization calls?
(It doesn’t seem to matter what version of openmpi I use).
Thank you
Claire
