Author: Gerd Isenberg
Date: 06:42:50 10/22/03
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On October 22, 2003 at 06:30:13, Sergei S. Markoff wrote: >Hello All! > >DS - is a term for using some features of classical evaluation that consists of >two parts - material and positional. >There are a lot of positions in that for one side material evaluation is >0 but >positional evaluation is <0 or vice versa. The root of big part of mistakes made >by modern engines is underestimating of positional eval because the positional >evaluation is constructed of several "atomic" factors. The _sum_ of this factors >frequently isn't good positional evaluation (anyway there are a lot of >"palliative" methods to avoid this problem like evaluation the relationship >between several factors). We can't fully trust positional evaluation and that's >why most of modern programs using a small values for a lot of factors. >The idea of DS is to use disagreement between positional and material >evaluation. There are a lot of ways how to use it. For example we can check >nodes in which sum_eval < alpha, but positional eval is large (for example we >sacrificed a pawn for attack e.t.c.). For this nodes we can: >1. Rebuild quiescence to include checks e.t.c. >2. Extend search >3. Change eval for the case of losing pawn or quality (trade bishop or knight >for rook) for big passed pawn / king attack eval. >4. Do assymetric eval. >5. Something else? > >Do you have some ideas in this area? > >Best wishes, >Sergei Hi Sergei, very interesting stuff. I'm currently using some feedback from eval to control search's behaviour, mainly (leaf node) extensions. Even if huge positional terms compensate each other, e.g. passers versus king safety. May be other search algorithms than alpha-beta are more convenient to handle such DS stuff to back it up to the root. Gerd
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