Author: Johan de Koning
Date: 23:51:36 08/13/03
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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
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