Author: Uri Blass
Date: 06:31:57 12/24/04
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On December 24, 2004 at 07:04:59, Joachim Rang wrote: >Hi, > >in the next hour Leo will add the new Fruit 2.0 on his website. The new version >comes with source as usual. Binaries for Linux come (perhaps) later. > >The biggest news: Fruit is no longer a blitzer! Fabien made a risky decision to >activate history pruning with rather aggressive values, so you will notice Fruit >prunes away a lot and reaches good depth rather soon. This makes him most >probably weaker in lightning or blitz, but will (hopefully) pay off in longer >time controls. If you aren't satisfied with the blitz-performance of Fruit try >deactivating history pruning. I think that history based pruning when used in the right conditions is not counter productive at blitz. You can try movei at blitz with history based pruning and without it. My impression was that the main advantage of it is in blitz based on the last time that I tested movei with and without history based pruning in test suites. You can disable history based pruning in movei by changing limit_history_depth from 101 to -1 You can reduce history based pruning in movei by increasing selectivity from 7 to bigger number but there is some pruning that will always remain so pruning does not converge to 0 by increasing selectivity. The problem is that I have condition: badvalue>(goodvalue<<selectivity) selectivity=7 means that you prune the move if the number of fail low is more than 128 times the number of fail high(there are more conditions and it is only one of the conditions). The problem is that this condition can happen also when goodvalue=0 and badvalue is small(there are more conditions so pruning when badvalue<=4 and goodvalue=0 is not possible but pruning when badvalue=5 and goodvalue=0 may be possible and how much you increase selectivity is not important. Note also that big selectivity may cause the value of goodvalue<<selectivity to be wrong. I divide goodvalue and badvalue by 2 everytime when the remaining depth is at least 10 and badvalue>1000 practically if I analyze the opening position for some minutes I find that always goodvalue<(1<<15) and I guess that practically in games I have always goodvalue<(1<<25) so it is no problem with the default parameters. > >The threshold of history pruning is set to 60%. Can you explain what it means? Source code is free so it is possible to look at the source code but I prefer first to read some explanation in words. I also see no reason that the parameter must be the same for different time controls and the program may use the time control and the hardware to calculate the parameter. Uri
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