Author: Uri Blass
Date: 00:49:40 07/04/02
Go up one level in this thread
On July 03, 2002 at 14:29:17, Robert Hyatt wrote: >On July 03, 2002 at 13:46:17, Christophe Theron wrote: > >>On July 02, 2002 at 20:20:37, Robert Hyatt wrote: >> >>>On July 02, 2002 at 18:54:49, Keith Evans wrote: >>> >>>> >>>>Sorry to be anal retentive, but that's a bit of a stretch. Here's what they say: >>>> >>>>"The chess chips optionally support the use of an external FPGA (Field >>>>Programmable Gate Array) to provide access to an external transposition table, >>>>more complicated search control, and additional terms for the evaluation >>>>function. In theory this mechanism would have allowed the hardware search to >>>>approach the efficiency and complexity of the software search. Null move search >>>>was also explicitly supported by this method. Due to time constraints, this >>>>capability was never used in Deep Blue." >>>> >>> >>> >>>Read on. On page 67, section 4.1, item 3, "mate threat". >>> >>>"It is relatively simple using a null move search to detect if there is a >>>threat in the current position.... The Deep Blue implementation ... >>> >>>Which matches what I said. They had support for a normal null-move search >>>had they wanted to use it, but they did use null-move to detect threats, >>>something that has been done before (and several of us use a form of mate >>>threat extension based on this idea presently). >>> >>>So they used null-move in at least one way, without using it as a forward >>>pruning algorithm, which fits with Hsu's "no errors in the search" theme he >>>mentioned repeatedly over the years. Extra extensions were one thing to him, >>>but outright errors were something else not to be tolerated. Right or wrong. >>>I obviously disagree about the errors in a normal null-move search, but I >>>can hardly argue with their success... >> >> >> >>That's my point as well. >> >>I don't argue about their success. >> >>I'm just saying that they succeeded because their chips were very fast. So fast >>that they allowed them to use inferior search techniques and still succeed. >> > >Could you not make the _same_ statement about chess 4.0 in 1975? Until that >point _everybody_ was doing forward pruning like mad. They discovered that a >a shallower full-width search had fewer errors and they stomped everybody into >the ground until everyone converted... It is different. It is obvious that selective search from the first plies is a mistake when you have speed. It also seems obvious that pruning rules that are based on the remaining depth is a good idea and you can use them and see everything if you search deep enough. Uri
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