Author: Robert Hyatt
Date: 05:49:19 03/12/99
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On March 12, 1999 at 02:26:49, JW de Kort wrote: >Hi chess friends, > >I have a small basic question about MVA/LVA move ordering. I have come across >this methode a few time, but i'am not sure what it accectly means? > >Does it mean to sort captures: > >1. Acoording to the difference of the capturing piece and the captured piece > >or > >2. Sort all captures first using the piece value of the most valued captured >piece and as a second critrium use the value of the capturing piece. this is close. You simply find (a) the most valuable piece (victim) that is under attack. You then capture it with the least valuable piece that is attacking it (aggressor). MVV = most valuable victim, LVA = least valuable aggressor (or attacker). This started in Belle, because it is a logical way to generate capture moves in hardware. Belle had two hardware things it could do (1) enumerate all squares that are under attack and find the one with the most valuable piece (the MVV part) and (b) for that square, find all the pieces attacking it and choose the least valuable one as the move to try (the LVA part). It is ok for hardware. But tests I ran a couple of years ago showed two important things: (1) using a static exchange evaluator gives more accurate move ordering. IE which do you want to try first, QxP where the pawn is undefended or QxR where the rook is defended? MVV/LVA will take the rook. This reduced the size of my tree by something over 10%, but the SEE algorithm costs me 6-8% so I don't get a lot out of that. But then there is (2) once you know that a capture loses material (ie QxR ?XQ) you can cull that capture completely and not even consider it. This can reduce the size of your search by 50% more. And _that_ is signficant. As it is close to another ply of depth. > >e.g suposse we have the following possible captures: PxN, PxR, QxR > >using methode 1: PxR, PxN, QxR >using methode 2: PxR, QxR, PxN > >Wich one is MVA/LVA? > >Thanks in advance > >Jan Willem
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