On Thu, May 16, 2013 at 11:45 AM, Mark Hahn <h...@mcmaster.ca> wrote:
> I found it unilluminating, actually. don't we all know about power issues? >>> >> >> Know? Yes. To this extent? Maybe not. >> > > OK, I can see that. to me, power is similar to a number of other issues, > which provide extreme limits to scaling. (power, reliability, net, > perhaps even storage and software complexity). from a CS background, > these all have distressing O()-type complexity, so each is clearly > a hard limit at some scale, given some level of technology. > > maybe I'm just more pessimistic ;) > > I guess I did think the flops power versus even on-chip communication thing > was interesting. but isn't the lesson to optimize for dataflow *and* > sometimes perform redundant computations? > > > forward and with a 20 Mw power budget, an exascale machine's network >>>> >>> would >>> >>>> consume all the power leaving nothing for computation. >>>> >>> >>> well, that sounds absurd - were they assuming a full-bisection fat tree >>> of >>> older (hotter, lower fanout) generation interconnect? >>> >> >> Even dragonfly topologies (high-radix routers with low hop count) and a >> bandwidth taper of 1/2 given current power consumption levels will exceed >> 20 Mw. >> > > anyone have an url on this topic? fundamentally, I've always reasoned > that since we exist in 3d, our networks need to be a 3d lattice at scale. > fighting power (flops, comm) seems like a noble, *engineering* fight, > but fighting our existence's dimensionality is silly... > We already exist in 3d - racks. We limit rack heights due to weight already (another item to add to your list of limits above). I understand that you are arguing for 3d is silicon (or other substrate), but there will still be a practical limit. I saw some presentation a year or two ago that showed an exascale system as a sphere with the switch complex in the center. It looked very 60s-ish, proto-EPCOTish... > yes, I would like to demo your new blackhole-based interconnect! ;) > Shouldn't it be wormhole-based? The blackhole-based one will just destroy the data, no?
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