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info about zappa on 512 cores ?
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Robert Hyatt



Joined: 27 Feb 2006
Posts: 15865
Location: Birmingham, AL
PostPost subject: Re: numa scaling    Posted: Tue Jun 26, 2012 3:34 am Reply to topic Reply with quote
Daniel Shawul wrote:
Quote:

You don't consider 50% as a significant variance??? I did look at the "test code" to see what it is doing, and it is purely a bandwidth measure. There is latency and there is bandwidth. Infiniband can provide bandwidth, but it is very slow in terms of latency when compared to a normal local memory access...

How did you come up with 50%. I considered the worst and best and it is about a 25% variation. Compared to the example given before, this machine seem more SMP than that one...


I took 6 and 9 seconds. difference = 3 seconds. 3 / 6 = 50%,,,

Not that it is very significant since that test code is primarily a memcpy() test which is bandwidth rather than latency. At a split point, you need some bandwidth to be sure, when doing the copy/split, but after that, it becomes more latency... And I am not sure what that box does with all the shared read-only data, if you plant it on one node, and make the others access over the infiniband switch, that would be an issue for sure...




Quote:

Quote:

The AMD approach, if you REALLY have 8 chips, is a large ring. And for each hop, the access time goes way up. With 4 chips, you have one local, two 1-hops, and one 2-hop access. With 8, it is 1 local, 2 1-hops, 2 2-hops, 2 3-hops and 1 4-hop, which gets sticky.

Crafty was tuned on a 4 chip AMD box... I have not done any sort of tuning (yet) for the newer AMD and/or Intel boxes where everyone is using NUMA now.


We have 3 clusters here that use infiniband, and while it looks great compared to other network topologies, it does not look great compared to actual memory over the bus..

The interconnect between cpus (quad-core opterons) is a HyperTransport bus.That is why it scaled well upto 8 procesors which it woudn't have it used infiniband. So you can't blame it on inifiniband.


Without knowing exactly how you are testing, exactly what the hardware looks like, scaling is difficult to discuss precisely. Normally, Crafty scales well on a normal AMD box (or Intel box). But I have not done a ton of testing on 6 core and up chips and have seen some issues there because with 6 cores, you can have 6x the demand, with the same HT hardware you have with just one core. So there is definitely a bottleneck. I just have not played around with any AMD hardware in quite a while since Intel has ruled the roost for several years in terms of chess performance...
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Subject Author Date/Time
info about zappa on 512 cores ? Daniel Shawul Sat Jun 23, 2012 2:05 pm
      numa scaling Daniel Shawul Sun Jun 24, 2012 10:20 am
            Re: numa scaling Robert Hyatt Sun Jun 24, 2012 5:01 pm
                  Re: numa scaling Daniel Shawul Sun Jun 24, 2012 5:41 pm
                        Re: numa scaling Robert Hyatt Mon Jun 25, 2012 12:37 am
                              Re: numa scaling Daniel Shawul Mon Jun 25, 2012 1:23 am
                                    Re: numa scaling Robert Hyatt Mon Jun 25, 2012 10:05 am
                                          Re: numa scaling Daniel Shawul Mon Jun 25, 2012 4:00 pm
                                                Re: numa scaling Daniel Shawul Mon Jun 25, 2012 5:21 pm
                                                Re: numa scaling Daniel Shawul Mon Jun 25, 2012 8:09 pm
                                                      Re: numa scaling Robert Hyatt Mon Jun 25, 2012 8:38 pm
                                                            Re: numa scaling Daniel Shawul Mon Jun 25, 2012 8:53 pm
                                                                  Re: numa scaling Robert Hyatt Mon Jun 25, 2012 9:17 pm
                                                                        Re: numa scaling Daniel Shawul Mon Jun 25, 2012 9:46 pm
                                                                              Re: numa scaling Robert Hyatt Tue Jun 26, 2012 3:34 am
                                                                                    Re: numa scaling Daniel Shawul Tue Jun 26, 2012 11:06 am
                                                      Re: numa scaling Daniel Shawul Tue Jun 26, 2012 12:55 am
            transposition tables Daniel Shawul Sun Jun 24, 2012 5:53 pm
                  Re: transposition tables Daniel Shawul Wed Jun 27, 2012 11:17 pm
                        Re: transposition tables Ronald de Man Fri Jun 29, 2012 11:47 pm
                              Re: transposition tables Daniel Shawul Sat Jun 30, 2012 12:40 am
      Re: info about zappa on 512 cores ? Vincent Diepeveen Fri Jun 29, 2012 11:07 pm
            Re: info about zappa on 512 cores ? Daniel Shawul Sat Jun 30, 2012 12:32 am
                  Re: info about zappa on 512 cores ? Daniel Shawul Sat Jun 30, 2012 10:50 am
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