[Beowulf] Cheap SDR IB

Mark Hahn hahn at mcmaster.ca
Wed Jan 30 13:49:11 EST 2008


> Bandwidth is one aspect of an interconnect. Other aspects are
> of course latency, CPU overhead etc etc. Some application will
> benefit from the latency, and some form bandwidth and some
> from a combination of all. Weather codes will show great benefits,
> and also CFD, rendering, bio codes (NAMD etc), Monte Carlo simulations
> and even mathematica users. Just a partial list.

duh.

>> IB for gaming?  I have one ratio: 1e-1/3e-6.  that's human
>> reaction time versus IB latency.
>
> Oh yes... I guess you did not play for a long time. Did you? Talk

I understand human psychophysics and I understand cluster performance.
I have never spent much time playing games.  it is perhaps ironic that 
my wife is a psych professor who _does_ actually study psychophysics
and behavior, including gaming.  humans really do run at only about 
100 Hz, so whether the interconnect is 1 or 50 us is really really 
not going to make a difference.

> with someone who suffer from lagging and you will get the story, even

I suspect you are referring mainly to wide-area gaming, which is 
so entirely different as to be not comparable.  it's certainly true
that wide-area gaming suffers network issues, but isn't that equally
obvious?  cable-modem congestion, for instance, or geographic 
timelag has no bearing on this IB-gaming idea.

> When he has a great video card. It's the network and the CPU overhead
> that are the cause of this issue

thanks for reiterating the obvious again.

>> PS: does anyone have first-hand experience with ConnectX performance?
>
> I do, but you probably want to hear from Myricom ... :-)

why the heck do you think I did not mean exactly what I said?
I would be most interested in hearing from someone who has bought
and is using a connectx cluster, especially the latency they experience.
in fact, my comparison would be to our elan4 clusters.
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