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Subject: Re: late move reductions

Author: Volker Böhm

Date: 00:40:36 03/02/06

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Hi Bob,

for Spike I discovered the following:

Statistically most fail highs occures at the first three moves. The fourth move
has again some fail highs, all others have very little fail highs.

History based reduction gains at max. 20 Elo compared to a simple move ordering
based reduction (allways reduce after move 3). The move ordering is based on
history thus this is again some sort of history based pruning.

Typically Spike plays better if more is reduced, I hardly found any
"less-reducing" rule that is better. Thus the test you are doing will show
little success for Spike as it will quickly drops beyond the "allways reduce"
level.

In consequence the calculation of the history reduction threshold is very easy
in spike. Every time a move fails high it gets one point and every time a move
does not fail high (but a later move does) it is reduced by one point (there is
some depth related factor). Below zero: reduce; above zero: don´t reduce.
Surprisingly the value of a move does not grow too much and gets relative
stable.

Greetings Volker



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