Author: Dann Corbit
Date: 18:39:28 10/07/02
Go up one level in this thread
On October 07, 2002 at 21:35:23, Robert Hyatt wrote: >On October 07, 2002 at 19:40:16, Tom Kerrigan wrote: > >>1. Deep Blue _did_ do forward pruning. They used null move for threat detection, >>not forward pruning, but they did have "domain specific" forward pruning. Hsu >>emphasized this quite a bit. He said specifically that it was responsible for >>allowing them to search critical variations very deeply. >> >>2. Deep Blue did _not_ have impossibly sophisticated eval terms. Hsu gave two >>examples of DB's "extremely costly" eval terms: >> >> i. Seeing if an open file is valuable by calculating the square control of >>the 7th and 8th ranks of the file (including rays) >> ii. Doing king safety calculations for both sides of the board while the >>king is uncastled. >> >>Many PC programs calculate square control and could easily/cheaply implement >>(i), and (ii) is not THAT expensive. If king safety takes 10% of a PC program's >>time, doing it twice would only make it 10% slower (and only in positions where >>kings aren't castled). >> >>Moreover, Hsu said that a major limitation of DB1 (that was fixed in DB2) was >>that square control information could only be used for a limited number of eval >>terms, apparently because it was available late in the eval pipeline. So there >>were limitations to the eval terms that could be computed by DB. > > > >A couple of points. (1) nobody said they had "impossibly complex eval terms". >I (and the DB team) _did_ say that they could do whatever they wanted. If >something is ready "too late" all you need to do is extend the pipeline a cycle, >and let -er rip.... _if_ you really want that eval term and it is serially >based on >something that has to be computed first... Compare that to what _we_ have to >do which is to serially compute _everything_. (2) what is so important about >DB1? DB2 was _the_ machine... and he fixed a _lot_ of problems from DB1 >in the re-design... > > > > >> >>3. There _was_ an implementation of DB's algorithms in software. I asked how the >>new eval terms in the DB2 chips were tested & tuned without actually having the >>chips, and Hsu said that Joel Benjamin played a "software simulation" to test >>them. He made it sound like that should have been obvious. (Are you listening, >>Bob?) > > >Never said there was _not_ one. I said "there was no reasonably efficient >software implementation" that could be used in an engine." Big difference. >You _can_ emulate _anything_ in software, by definition. But that doesn't >mean you can use it to play games... > >They discussed their "software tuning" more than once, and apparently had some >sort of GUI interface to the process... > > >> >>4. While he does have the rights to the DB chip design, Hsu is still bound by >>IBM NDA for the eval terms and is not legally allowed to disclose them. >> > >Nothing surprising there. The software tuning algorithm is found at Tim Mann's site. Also included is the data that was used to drive it. If you have a POSIX workstation, you will even get the icky curses interface along with it.
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