[Beowulf] New HPCC results, and an MX question

Patrick Geoffray patrick at myri.com
Tue Jul 19 21:38:35 PDT 2005

Greg Lindahl wrote:
> On Tue, Jul 19, 2005 at 11:11:33PM -0400, Patrick Geoffray wrote:
>>If you randomize the machine list, then there is no difference
>>between the random ring latency and the average pingpong.
> Patrick,
> There likely will be a difference, because average pingpong doesn't
> run on all the cpus. On a 4-cpu node, that can make a big difference.

I believe the difference will not be that big. I will get my hands on a 
quad in the next couple of weeks, I will look into int.

> To give you an example, look at the Quadrics reported numbers for
> random ring latency of 11.4568 usec and average ping-pong of 1.552
> usec. This is on a 2-cpu node (I think). I'd bet that most of this
> difference has nothing to do with machine size. But I'd be happy to be
> proven wrong.

I would think 1.5 is shared memory in this case (all pairs are ordered 
and they end up being on the same nodes). This is one of the thing I 
don't like with HPCC, so much variation in results depending on size of 
clusters, process mapping, order/topology.

> Hopefully someone will publish a Myrinet MX-based set of HPCC results
> soon. (hint, hint!)

I don't have time to do that. At least, as long as HPCC, like HPL, take 
a gazillions parameters. Give me HPCC with no parameters and I will take 
5 minutes to start it. I was promised it would be this way eventually.

I don't believe much in any analytic benchmarks. HPL can yield 90% of 
peak if rewritten for modern MPI implementations, Pallas is nice to find 
out when something is very wrong, but not much more, and the NAS are 
marginaly more interesting.

I prefer benchmarking real codes, and we will publish that, but 10G is 
taking most of my time these days (got to get something for you to 
compare against).

>>I know, tongue-in-cheek. Will you publish the raw numbers on the web 
>>site eventually ?
> Yes. That's what I meant in the first place.

I bet the next time you won't :-\


Patrick Geoffray
Myricom, Inc.

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