Author: Robert Hyatt
Date: 21:25:58 09/11/04
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On September 11, 2004 at 11:17:35, Charles Roberson wrote: > > This discussion brings out an interesting thought. I agree with all of > Bob's statements, but how about a change of use? > > Lets assume a single stage cache and replacement scheme of > current depth > previous depth. Also, we have a collision test to ensure > we really are on the same position. If you do simple depth-preferred you will crush performance, as your table will fill with deep draft entries and local sub-trees can't store anything at all.. That is a known problem and is the primary reason for the two-tier Belle approach many use... > > Now, the PV is set but in a later tree branch one of the PV positions > is overwritten due to greater search. True this changes the PV from what > you originally setup but there may be a positive side effect of this. > > If we only allow the last few moves of the PV to be changed by hash > replacement(I can think of two ways to do this) then wouldn't we get better > moves for the PV tail? Thus, improve move ordering for the next iteration due > to a somewhat better PV? > > Charles Remember that two different positions can map to the same table address, even though the hash signature is different. Short PV = bad move ordering. Also if you do only depth-preferred hopefully you will prefer exact over upper or lower entries, and that leads to lots of problems with the wrong PV move that comes from a _shallower_ search than the real PV move...
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