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Subject: Re: MVVLVA sorting does not help for move ordering

Author: Uri Blass

Date: 22:20:00 09/21/02

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On September 21, 2002 at 18:09:27, Severi Salminen wrote:

>>3. winning captures ordered by MVVLVA
>>4. other moves
>>5. losing captures
>>
>>My updated move ordering is:
>>1. from hastable first
>>2. killers next
>>3. all captures, ordered by the size of the captured piece (largest first), and
>>ties broken by size of attacker only
>>4. other moves
>>5. losing captures
>
>With MVV/LVA you can never know if a capture is a losing capture.

I guess that he first evaluates which captures are losing captures and later
sort only the good captures by MVV/LVA.

Today I also do it(I have ideas to improve it but it is more easy to think about
ideas then to implement and it was not in the top of my priorities).

The way that I do it today is to tell movei that if the attacker is bigger than
the victim and the square is defended by the side of the victim and not by the
side of the attacker the capture is a bad capture.

I do not detect all bad captures by this way.

r1bqkbnr/ppp2ppp/2np4/4p2Q/4P3/5N2/PPPP1PPP/RNB1KB1R w KQkq - 0 1

I do not detect that Nxe5 or Qxe5 is bad because white has more than one piece
to attack e5 but at least I detect Qxh7 or Qxf7 as bad captures.

I also may be wrong in detecting bad captures inspite of the fact that I do not
include all bad captures

Here is a simple example:

[D]4kbn1/6pp/5p2/4p3/4P1r1/3P1N2/4BPPP/4RK2 w - - 0 1

Nxe5 is detected by movei as a bad capture but it is a good capture.

 And only if
>the victim is more valuable piece than aggressor , you can be sure it is a
>winning capture -

Even then you cannot be sure
Here is a simple example

[D]4kbn1/6pp/5p2/4r3/4P1b1/3P1N2/4QPPP/4RK2 w - - 0 1

Nxe5 is a bad capture but today movei does not detect it as a bad capture.

Uri



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