p4 v itinium
becker at scyld.com
Fri May 17 14:23:00 PDT 2002
On Fri, 17 May 2002, Josip Loncaric wrote:
> based on domain decomposition, the optimal amount of memory per node
> grows very quickly as a function of the CPU/communication speed ratio.
This comes as a surprise to many: as processor performance increases:
the per node communication requirement grows less rapidly than expected, but
the per node memory requirement grows faster than expected.
> If you double the CPU speed but keep the same network, you can maintain
> performance if your domain volume/surface ratio doubles as well. This
> can happen if the volume (computations) grows by a factor of eight and
> surface (communications) by a factor of four. In other words, per node
> memory requirements can grow with the cube of the CPU/communication
> speed ratio.
This paragraph should be the canonical response when people ask about
the future communication and memory needs on a cluster. Not every
problem is a physical finite element grid, but that's the easiest mental
model when explaining trends.
Donald Becker becker at scyld.com
Scyld Computing Corporation http://www.scyld.com
410 Severn Ave. Suite 210 Second Generation Beowulf Clusters
Annapolis MD 21403 410-990-9993
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