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Subject: Analysis and tablebases puzzling behaviour

Author: James Constance

Date: 09:05:27 12/12/05


[D] 6q1/4K3/1k6/7Q/7P/8/8/8 b - - 0 79

I noticed a problem with engines in accessing the tablebases.  FOr instance when
analyzing this position Fritz 9 gives approx -2 evaluation. If Qg7 is played,
the eval is Qf7 gives #75. If then Qf7 is played the engine starts evaluating
again, and so on.  So with white to move Fritz seems to access the tablebase and
gives a mate in eval, but with black to move it doesn't seem to access the
tablebase.

The same occurs in Shredder Classic: After Qg7 is played the engine analyzes.
After Qf7 is played it shows M74 immediately.  Then if Qg2 is played, Shredder
starts analyzing h5 as the best move (which only leads to a draw).

I notice this doesn't occur with Junior 9 (after the first couple of plies of
analysis (scroll main line) it shows the M75 with either side to move).

Can anyone else duplicate this?  And what the heck is going on? :)



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