Author: Robert Hyatt
Date: 06:19:23 08/24/01
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On August 24, 2001 at 04:31:27, Tony Werten wrote: >Hi all. > >I like to know if there are some solutions for this problem. > >My program searches for 4 minutes, gets to 14 ply (or whatever), makes a move, >takes a pondermove and starts pondering. > >Now the first 12 ply are taken from the hashtable (<1 sec ) but it starts an >(almost) uninformed 13 ply search from which it is never going to return in the >allocated time, so it's just taking the best move it had from the previous >search, which is costing me plydepth. (and games ) > >Any ideas, sugestions ? > >cheers, > >Tony Internal iterative deepening can help here. The problem is that if your first move comes from the hash table with a good score (typical on pondering) then you reach depth N with a PV that has only that move in it. (there are things you can try to do, such as extending the PV in such cases by probing for the second position, etc when you back up the PV). IID works by doing shallow searches to find good moves at PV-type positions where you have no PV move. If you don't do something like this, you reach critical positions with no real hope of having the best move searched first, which makes the tree explode in a bad way... You can see how I implemented IID in Crafty. It is actually pretty simple, so long as you have an easy way to search the same position twice without causing your data structures any sort of problems..
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