Author: Robin Smith
Date: 14:50:28 08/15/03
Go up one level in this thread
On August 14, 2003 at 02:51:36, Johan de Koning wrote: >On August 13, 2003 at 17:53:30, Dieter Buerssner wrote: > >>On August 13, 2003 at 03:00:10, Johan de Koning wrote: >> >>>On August 10, 2003 at 13:57:00, Amir Ban wrote: >>>>The log doesn't show what J8 was thinking. Apparently it thought it was mating , >>>>because it played all moves in 0 seconds. >>> >>>Yet another good reason to clear out the TT at the start of every search! >>>:-) >> >>Or to use the time to find a shorter mate, even when seeing a mate already. > >Indeed, but that didn't suit my point. :-) > >>What are the other good reasons for clearing TTs? > >1. Predictability > IMHO an engine should just search when a search is needed. > After all it is a tool, not a living creature. >2. Reproducibility > Playing and watching games is the best way to spot funny behaviour. > Not being able to find the cause of this behaviour is pretty frustrating and > may leave unintended features unnoticed. >3. Complexity > Sticky TT requires more data and more code (= more bugs). > Complexity is not a big deal once you've got it right and you're not ever > going to (want to) change things. But that's theory. >4. Preprocessor > A change of the root position might render all TT entries invalid. > Though preprocessing is not as important as it was in the 1980s, I bet most > engines compile at least wood and placement tables based on the game stage > of the root position. >5. Pondering > If an engine has pondered the wrong move, the TT will be overwritten with > positions that are either useless or have the wrong bound. >6. Time management > Admittedly implementation dependent, but the stability of the root (drops, > move changes) is useful infomation. The time manager may get confused if > this information is lost. >7. Unforeseen problems > Eg the perpetual mate that started this thread. Rather funny actually, if it > happens to someone elses engine. But more importantly, rather instructive. > Besides the infamous incomplete-EGDB-problem we now have the infamous > incomplete-TT-problem. :-) > >... Johan Johan, For someone who uses chess engines to do analysis, rather than just playing games, clearing Ttables is a serious flaw. Robin
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