Author: Vincent Diepeveen
Date: 10:39:08 11/11/02
Go up one level in this thread
On November 11, 2002 at 13:18:12, Russell Reagan wrote: That's how the OS reports it to you. In fact i have different statements here from different OS experts. One of them said for example: "in console this OS (without quoting which OS he referred to) i measured for my application A that i saved out up to 10% in speed". I am no expert here, but at least his words made sense. If many threads are running at an OS, then i can imagine that switching each 0.002 seconds to another thread is going to cause damage. Context switching of the processor etcetera. At todays processors however it won't be 10% i bet. So taking that into account, basically the compiler matters a lot. Nowadays however compilers work for different OSes. I do not know how good compilers are for mckinley/R14000/alpha/Sun when compared to X86 compilers. I get impression that the x86 compilers have made up a lot of terrain. the alpha compiler was said to be very very good, but it never impressed upon DIEP in fact. Speeds at alpha were horrible. On the other hand others reported the Sun to be a horrible processor/compiler combination, but DIEP ran fine at SUN cpu's. McKinley is very fast for DIEP (1Ghz Mckinley like a 1.33Ghz K7 even) but i have no idea how well its compiler is compared to other processors. If i compare the specs from the K7/P3 versus the McKinley, we see a major difference in specifications: K7 + P3 can do up to 3 instructions a clock McKinley is doing 6 instructions a bundle (if i understand well) K7 + P3 have horrible small L2 cache McKinley has *huge* L3 cache 3 MB even Yet it is only 33% faster or so. With some more fine tuning i might get it bigger. I wasn't capable yet to check out what branch prediction means for it. In general i have *no* idea what the OS eats from those processors. I get impression however that the OS gets more important at SMP machines than it is at single cpu machines. Basically these compilers which usually only works for 1 or 2 OSes, determine what speed you get under that OS, because even if it would be an incredible 10% which the OS eats (hard to believe for me it would be that high for todays OSes) then that still means peanuts compared to what a good compiler can save you out. >On November 11, 2002 at 13:02:44, Bob Durrett wrote: > >>Would the engine perform significantly better using that dedicated operating >>system? [As compared to using a commercially available OS] > >You can get an idea of how much time is used by the OS. On my computer I look >under Task Manager and it says: > >Image Name CPU Time >System Idle Process 6:19:14 >IEXPLORE.EXE 0:02:16 >msdev.exe 0:01:22 >Explorer.exe 0:00:53 >System 0:00:22 > >And so on. So I have over 6 hours of idle time, and the next biggest chunk of >CPU usage time was by Internet Explorer, of a whole 2 minutes. That means there >is 99.5% of the CPU time that could have been used by a chess program. So the >question is whether or not a 0.5% increase in speed is going to mean >"significantly better" results. I think not.
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