Author: Tord Romstad
Date: 07:41:29 01/15/04
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On January 15, 2004 at 09:56:26, Volker Böhm wrote: >On January 15, 2004 at 08:06:34, Tord Romstad wrote: >>I generate safe moves for hanging pieces if all of the following are >>satisfied: >> >>a) The value of the static eval is >= alpha. >> >>b) At least two of the pieces for the side to move is hanging. >> >>c) static_eval-(value of capturing the smallest hanging piece)/4 < alpha> >>d) I am in one of the first two plies of the qsearch. >> >>Always generating all safe moves for all hanging pieces is probably a >>waste of time. For instance, if you are a queen up, it is not very >>important to find out whether it is possible to save a hanging knight. >>And in positions with only one hanging piece, it will usually be safe >>to assume that the piece can be saved. Of course there are exceptions, >>but I think it is better to ignore them and use the time saved to >>search deeper. > >Hanging pieces in the qSearch?! I planned (not yet implemented) to search one >ply deeper if my eval reports: > >1. More than one hanging pieces (and pieces attacked by less valuable pieces). >2. A tied (hope this word is correct, I mean a piece that can´t move because it >has a king or a valuable or hanging piece behind) piece attacked by a "smaller" >piece. >3. Some kind of mate threads > >Tried this too? I do some similar stuff, yes. I don't usually extend in such cases (except for mate threats), but I am much more careful about reductions and forward pruning at nodes where there are hanging or pinned pieces. In addition, the null move reduction factor is often reduced (R=1 or 2 instead of my default R=3) at such nodes. >How did you implement the "hanging piece" move? In q-Search you are never >forced to move. In my qsearch(), you sometimes are. :-) In some cases when the static eval for the side to move is good, but it seems that there is a big danger of losing material (usually because there are at least two pieces hanging, or because there is a mate threat combined with at least one hanging piece), I don't always allow the qsearch to return the static eval. Tord
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