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Subject: Re: hash---what is really going on in ram

Author: José Carlos

Date: 05:55:33 03/14/01

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On March 14, 2001 at 00:51:02, K. Burcham wrote:

>ok so i boot up, start my program. set my hash to 128, with 384 megs of ram, and
>i start playing. when i start out the % of hash reads 0, and will climb to about
>50% in 30 seconds. does this mean that one stick of ram is at this point half
>full of positions considered? if yes, then after every move why does this
>percentage go back to 0. does this mean the ram clears after every move?

  Probably. Some programs clear the hash tables after every move, because their
evaluations depend on the root position, so the evals in the hash table are not
valid anymore.
  What program are you using?

>what is
>this 50% referring to? what is the 0% of hash, after every move  referring to?
>also i have noticed how fast sos and shredder5 will fill hash.

  Duno for shredder, but SOS is know to use MTD(f), and algorithm that uses HT
much more than others.

>i can see why
>stefan always had a very large amount of hash in his tournaments, 768 megs. what
>are these programs doing in a long analysis, or in an all nighter? does this
>hash fill, and it just starts a read/write from the hard drive? or does the
>operating system constantly move these calulations to the hard drive to clear
>hash?

  The hash tables only work fine if they are everytime in RAM. If moved to the
hard disk, the performance gets very poor.

  José C.

>if yes, then during this file moving, from ram to hard drive, can we say
>that the program never "thinks" to the hard drive (excluding tablebases), and
>only thinks (stores nodes) to  ram?
>
>thanks      xracer



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