Author: Robert Hyatt
Date: 10:53:13 03/27/01
Go up one level in this thread
On March 27, 2001 at 13:34:12, Vincent Diepeveen wrote: >On March 27, 2001 at 09:36:54, Robert Hyatt wrote: > >>On March 27, 2001 at 08:52:15, Andrew Dados wrote: >> >>>On March 27, 2001 at 08:17:43, Vincent Diepeveen wrote: >>> >>>>On March 26, 2001 at 22:44:53, Robert Hyatt wrote: >>>> >>>>>On March 26, 2001 at 20:54:48, Dan Andersson wrote: >>>>> >>>>>>I have to agree that multibanked memory and lage cashe size are very beneficial. >>>>>>Those factors could very well explain the superlinearity. >>>>>> >>>>>>Regards Dan Andersson >>>>> >>>>> >>>>>I don't think the 4-way interleaving helps. That _barely_ lets the machine >>>>>hold its own, memory-wise, because there are 4x as many cpus fighting over >>>>>access to memory... making it nearly 4x faster just barely breaks even. The >>>>>larger L2 cache may well make a difference, of course... >>>> >>>>You speak for Crafty. I speak for DIEP. >>>>I'm doing 8 probes of at least 16 bytes an entry. >>>>that's 128 bytes. >>> >>>My guess is big difference for SMP DIEP is running separate processes instead of >>>threads. 8 probes is just icing on that cake. >>> >>>For what I know windows (unix too) will load each process to its own address >>>space, so they will fight for L3 cashe. >>>Or am I totally wrong here? >>> >>>-Andrew- >>> >> >>This is correct. Threads share one address space so this isn't such a huge >>problem... > >but your program with threads is slower as you need extra pointers >everywhere except if you start using non-ansi C standards. > >How do i evaluate a board position in ansi-C using multithreading >without needing to load an extra pointer? > > > This is a moot issue. I mentioned before that when I first converted to the pointer approach, I was expecting a huge performance hit. In reality it was less than 7% and over time that dropped to under 5%. I would bet that that 5% is swamped by the advantage of having one large common virtual address space which prevents continual cache flushes...
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