[Beowulf] Help with inconsistent network performance

[Peter St. John]

Brendan,

I'm a day late but maybe not a dollar short :-) When I read the original
question, I was going to ask, "do the compute (render) nodes push their
results when ready, or does the head (view) node pull?" and from the
subsequent discussion and clarifications it seems to be the former. And yeah
what Mark said.

So if it were me, each compute node would send the (short) message, "I'm
ready"; the head node would maintain a list of ready nodes, and pull from
them sequentially ("Ok node number 7, upload now please"). That way the only
collision is word-sized and not image-sized, and the overhead is trivial.
But that would be me using FTP and tcsh :-)  Dunno what you'd do
specifically with the software you have.

Peter




> (Hahn)
> it's the _timing_ of the data.  using bcast, you attempt to cause the
> render nodes to, as simultaneously as possible, saturate their own
> links, and therefore (N-1)-times oversaturate the viewer link.
>
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