These are long integers, right? Otherwise the array could almost fit into 4MB cache of Itanium or Woodcrest.
However even this would not be enough for Power5 which has a massive 36 MB L3 cache. By the way, we have Power5 and PowerPC available if you want. > I wrote a pthread based latency tester that will access N integers > randomly per thread. Each member of the array is accessed once. > All the numbers below are for N=1,000,000 integers. Every integer is > loaded exactly once, randomly. > > The first number is the latency per thread, so it increases with memory > contention. The second number is the "effective" ns, where I divide > the run time[1] of all threads and divide it by the integers retreived. > It should decrease with increased threads if the machine has the CPU > and memory system parallelism to avoid contention. > > 1 thread 2 threads 4 threads > Dual Opteron 275[2] 83.69ns/83.69ns 80ns/52.08ns 85ns/21.72ns > Quad opteron 846[3] 108.07/108.07ns 115ns/61.39ns 110ns/27.89ns > Dual Woodcrest-2.66[2] 107.18/107.18ns 108ns/54.03ns 118ns/29.69ns > Dual core amd64-2.2GHz[5] 89.45/89.45ns 89.45ns/44.72 145ns/52.76ns > AMD64 3200[4]-2.0GHz 69.74ns/69.74ns 69ns/69.31ns 137ns/69.85ns > Dual socket nacoma 3.4GHz[6] 130.45/130.45ns 133/66.72ns 230ns/67.72ns > Dual core p4-3.0[6] 115.45/115.46ns 185ns/101.03ns 283ns/92.67ns > Dual it2-1.4GHz[6] 200.47/200.47ns 203ns/101.92ns 362ns/101.57ns > > I'm happy to say that Pathscale, Intel, GCC-3, and GCC-4 all share > mostly identical performance. Although, I had to be very careful with > pathscale to avoid the benchmark routine from getting optimized away. > > Anyone have a Rev F opteron handy? > > [1] Where runtime = max(finishtimes)-min(starttimes) > [2] Dual socket, dual core = 4 cores > [3] Quad socket, single core = 4 cores > [4] Single core/single socket = 1 core > [5] Dual core/single socket = 2 cores > [6] Dual socket, single core = 2 cores. > > -- > Bill Broadley > Computational Science and Engineering > UC Davis > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org > To change your subscription (digest mode or unsubscribe) > visit http://www.beowulf.org/mailman/listinfo/beowulf > _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
