[Beowulf] Computation on the head node
Jeffrey B. Layton
laytonjb at charter.net
Mon May 19 12:59:02 EDT 2008
Perry E. Metzger wrote:
> "Jeffrey B. Layton" <laytonjb at charter.net> writes
>>> In any case, let me note the most important rule: if your CPUs aren't
>>> doing work most of the time, you're not allocating resources
>>> properly. If the task is really I/O bound, there is no point in having
>>> more CPU than I/O can possibly manage. You're better off having 1/2th
>>> the number of nodes with gargantuan amounts of cache memory than
>>> having CPUs that are spending 80% of their time twiddling their
>>> thumbs. The goal is to have the CPUs crunching 100% of the time, and
>>> if they're not doing that, you're not doing things as well as you can.
>> I absolutely disagree.
> Chacun a son gout. I was under the impression that in scientific
> computing the name of the game was having your computation done as
> fast as possible at the lowest possible cost.
> If your CPU is idle, why did you pay for it? They're a huge cost
> differential these days between fast and slow CPUs. Why didn't you buy
> a much cheaper CPU that would remain nearly 100% busy while keeping
> the I/O subsystem as fast? You would have saved lots of cash, your job
> would be done just as fast, and probably (in a modern system) you
> would have saved a whole lot of electricity because slower CPUs eat
> fewer Watts.
Evidently you don't know jack about real codes. In addition, I've gotten
some off-list messages that you have already been added to a number of
kill files as a troll because of you inability to listen, understand,
plus your off-list obnoxious emails. I've joined the gang in adding you
kill file. Enjoy.
>> I believe you're thinking of local IO - like a desktop.
> No, really, I'm not.
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