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[Mark Lefler]

I tried something like that a long time ago (not extending checks if way ahead in material). I did not such a high margins (8 pawns) though, so that might matter a lot. I did steal Tord's idea of not including chekcs in the qsearch if way ahead in material...I have not idea if it helps, but it makes a lot of sense.

I also think maybe extending even losing checks might make sense if the score is under 0. Capturing say a P with a N, and losing the knight might just expose the king to perpetual checks or something. I should experiment with this.

The conditiions I sent in the original message give me 40-50 ELO score improvement in otherwise identical programs that always extends all checks, but I only played a couple of hundred games, so this might not be useful. Tests against a bunch of programs also showed a small improvement, but again I would need 10000 games or somehting to have confidence.

Another idea is to force a full ply extension for any check that has a single response. It would be less costly than a two ply extension (check and single response), yet still catch things like one side distracting a king by sacrificing something to put it out of the range of protecting something more important.

If only I had Bob's cluster to try out 1900 ideas at once!

Mark