On Mon, May 06, 2013 at 02:30:15PM -0500, Bob Cernohous wrote:

...

From: Rob Ross <[email protected]>

Should we consider this as interest in working on this problem on the IBM side :)? -- Rob

Say what?! ;)

RobR's excited that IBM's looking at the ROMIO piece of DCMF. We thought we were on our own with that one.

I was looking more for agreement that collective i/o is 'what it is'... and maybe some idea if we just have some known limitations on scaling it. Yes, that BG alltoallv is a bigger problem that we can avoid with an env var -- is that just going to have to be 'good enough'? (I think that Jeff P wrote that on BG/P and got good performance with that alltoallv. Trading memory for performance, not unusual, and at least it's selectable.)

I can't test while our Blue Gene is under maintenance. I know the environment variable selection helps only a little bit (like improves scaling from 4k to 8k maybe? don't have the notes offhand). ==rob -- Rob Latham Mathematics and Computer Science Division Argonne National Lab, IL USA