Jeff Squyres wrote:
On Oct 25, 2007, at 12:11 AM, George Bosilca wrote:
Now you cast a doubt on me. As far as I remember, there is a trick
in MPI2 to do this. You can merge your inter-communicators into one
intra-communicators with MPI_Intercomm_merge and then use
MPI_Intercomm_create to spawn a new inter-comm over the 2 childs
world (using the common parent as a bridge process) ... I have to
try it to refresh my memory :)
If you have the following scenario:
- A spawns B, gets intercomm AB
- A spawns C, gets intercomm AC (that does not include B)
- ...repeat N times (e.g., to AN)
well, how about the following for your example:
- D = intercomm_merge (AB)
- E = intercomm_merge (AC)
- F = intercomm_create (DC, using E as bridge-communicator)
- F' = intercomm_merge (F)
- G = intercomm_create ( BC, using F' as bridge-communicator)
not very nice, but should work...
Edgar
Then B and C are not even aware of each other (from MPI's
perspective). I can't think of an MPI operation to magically connect
all the previously-unknown-to-each-other MPI processes. You could
use COMM_ACCEPT/COMM_CONNECT or COMM_JOIN to connect B and C (and B
and D, and B and E, and C and D, and ...) and then you might have
some more options, but that might be even more trouble that doing the
cumulative COMM_SPAWN/INTERCOMM_MERGE.
George: if you know of some trick, it would be interesting to hear.
