Right, there is a mismatch between MPI handles and shared memory handles. IPC shared memory relies on having a portable handle (filename, etc) in order to support asynchronous attach/detach to/from shared allocations. In order to fully support this, we would also need to have a portable handle. There was an earlier suggestion of letting the programmer supply a handle. We didn't seem to like it, but that would get around the problem of needing to share and MPI handle. Another alternative would be to make attaching to a shmem region collective. This is tricky too since it would be collective across a new communicator that includes the added processes. We would also need a collective detach. ~Jim. On 2/17/11 2:27 PM, Jeff Squyres wrote:
In fact, chapter 2 explicitly says that handles only have meaning in the local process.
On Feb 17, 2011, at 3:19 PM, Hubert Ritzdorf wrote:
MPI_Comm_shm_attach() is a little tricky - in the current proposal I don't think we've defined the shm handle to be portable. Can we make it valid to send this to another node-local process in order for them to call attach?
Is there an example in MPI where we allow sending an MPI handle to object between ranks? This seems like a bad idea to me.
No, there isn't.
Hubert
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