Author: blass uri
Date: 23:46:45 05/09/00
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On May 10, 2000 at 00:23:30, Michael Neish wrote: > >Hi, > >I'd like to ask what people think of the depth at which programs seem to search >nowadays. I've read some posts and analyses on here that suggest that some >commcercial programs habitually search to depth 15 or more in the middlegame, >whereas other programs seem to take a long time just to get to depth 10 or 11. >Of course there are differences in search speed, but given the exponential >nature of the search tree it seems hard for me to believe that these programs >really are searching so much deeper than their contemporaries. > >Are they cheating somehow? Since ply depth is probably a strong selling point I do not think that customers are so stupid to decide on buying programs based on the ply depth. ply depth say nothing about tactical ability of programs even if you assume that the programs use the same extensions because tactical ability can be hidden in the evaluation function. Here is a simple example: A slow searcher may see when white has a knight at c7 and black has a rook at a8 and the black rook cannot move that the rook is lost when a fast searcher needs to search more plies to see that the rook is lost. , >as processor speed is for PCs, there is probably a strong motivation to try to >reach further than your contemporaries, at least on the surface. So, are these >programmers pruning the trees somehow (apart from the usual techniques talked >about here), or otherwise eliminating moves so that the search tree doesn't >expand as quickly? If so, isn't this search depth just illusory? Can >short-term tactics, well below 15 ply, be missed in this way? Null movers sometimes cannot solve mate in 2 because of null move pruning so the answer to your question is certainly yes. Another possible reason for missing tactics are a bug in the program or a decision not to see some things that usually do not happen. I found cases when Junior could not see a simple tactic but these examples are rare in practical games. Uri
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