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Subject: Re: Move ordering?

Author: Josť Carlos

Date: 16:15:59 04/28/00

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On April 28, 2000 at 17:22:24, Dann Corbit wrote:

>On April 28, 2000 at 17:01:20, Severi Salminen wrote:
>>My program finally has AB search, searches some 70 KN/S and it almost knows
>>every rule (no underpromotion, 50 move rule and position repetition :-). Now I
>>would like to add some move ordering. I have two simple ideas: at root I sort
>>the moves by scores from previous iteration and at other nodes maybe by
>>captures, checks and then others. Does this sound reasonable? Where could I find
>>more information on move ordering methods or what do you use?
>Sort them by time it takes to emerge from alpha-beta.
>The ones that take the longest get checked first.  Resort after each new level.

  I don't get the idea. First, when using PVS, PV move will always take more
time than the rest (if not fail high). But, omitting PVS, I don't still
understand why a move that takes longer should be searched first.

  What I do right now is:
  1.- in the first iteration, I sort the root moves exactly the same as the rest
of the moves (captures first, etc.).
  2.- after every fh, I assess that move a value greater that the others, so it
will be searched the first in the next iteration.
  3.- as new fh occur, the moves remain ordered as last_failed_high_first. And
the moves that never failed high, remain ordered by normal ordering heuristics.

  This method seems to work fine for my program.

  Josť C.

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