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Subject: Re: is the

Author: Roberto Waldteufel

Date: 06:00:29 07/21/98

Go up one level in this thread

On July 20, 1998 at 19:21:27, Dan Newman wrote:

>On July 20, 1998 at 17:02:51, Roberto Waldteufel wrote:
>>On July 20, 1998 at 15:20:24, Dan Newman wrote:
>>>On July 20, 1998 at 14:36:12, Bruce Moreland wrote:
>>>>On July 20, 1998 at 14:30:47, Dan Newman wrote:
>>>>>One of the biggest effects I see is that I get a much larger node rate
>>>>>the longer I run.  If I run a test for 10 s I might get 170 knps.  If
>>>>>I run for 40 s 200 knps.  It does level off of course.  I'm using a
>>>>>P6/200, so I've attributed this effect to improving branch prediction
>>>>>as the code runs.  Any ideas?
>>>>Maybe it has something to do with the deeper search having characterstics that
>>>>differ from the shallower search.
>>>I bet that's it or at least a lot of it.  The major difference is that
>>>the deeper plies will have fewer pieces on average.  So move generation
>>>will be a little cheaper, a smaller portion of the moves generated
>>>will be wasted, and so forth.
>>Have you considered that the deeper iterations contain the most transpositions,
>>so you will process more nodes quickly by hash table look-up? I think this must
>>surely account for at least some of the difference.
>>Best wishes,
>I hadn't thought about that either--but I've seen the effect even
>without a transposition table.
>Actually, I'm beginning to return to my original guess--I've noticed
>this effect when benchmarking the move generator in isolation too, just
>generating the same set of moves over and over.  The longer the run,
>the more move generations per second.  I imagine this could be due to
>the branch prediction hardware settling into an improved (but probably
>not optimal) pattern.  Or, it could be the OS doing a lot of stuff
>immediately after loading the program in--disk accesses or whatever.
>Just one more in a series of quirky, unfathomable computer behaviors.

Hi Dan,

Now that you mention it, the OS may well be partly responsible. This reminds me
of a peculiarity I have noticed running my program under Windows95. The program
uses about 44 MB RAM for storage, but my machine has 64MB which should be more
than enough spare to keep Windows happy. When I first load my program,
everything is fine. When I start play, the program thrashes the hard disk for
about 15 seconds, during which time the program runs very slowly. Afterwards
everything is fine. If I then quit the program and reload it, this disk access
does not occur again, but if I run another application in between, then I get
the disk thrashing at startup again. I know virtually nothing about Windows,
having only recently switched from DOS so as to use 32-bit code, but it seems as
if Windows is swapping a lot of stuff out of RAM to make room for the program
data while the program is actually running!

Best wishes,

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