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Subject: extensions

Author: Scott Gasch

Date: 14:57:01 08/18/99


Hi there,

By converting from standard negamax to a negascout search I made a dent in the
move branching factor and the program is searching deeper.  I also got razoring
working.

However razoring is kinda stupid without extensions and whenever I add
extensions to the search routine the program slows _way_ down.  I think the most
common extension is a check extension that is what I am implementing now.  So if
side to move is in check I am calling the recursive search routine with the
depth unadjusted...  This is 1000% slower than no check extensions :(

So I tried a thing that I don't understand completely but I see Crafty do and
have heard about before -- now my depth for one ply is 16 and I try fractional
extensions for check.  This still slows the program down a lot.

I originally thought this might be because of repeated positions and branches of
the tree going back and forth until the 50 move draw rule cut them off.  However
I just added a draw by repetition check that seems to work and still when I turn
on extensions it is  s l o w.

Does anyone have any thoughts about the pitfalls of extension that I might be
falling into?

Thanks again for the help.

Scott



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