Author: Wayne Lowrance
Date: 17:55:06 01/24/06
Go up one level in this thread
On January 24, 2006 at 20:15:31, Graham Banks wrote: >Rybka 1.01 Beta 12 >January 23, 2006 > > >Brief Overview > >Disclaimer > >This is an unpolished, untested release of the program. If you are a casual >user, we suggest that you save yourself potential trouble and continue using >Rybka 1.01 Preview 2 until the next more widely tested release is made. > >Release Audience > >Rybka Beta testers. > >Release Features > >1) Search changes (search work is now finished for the Rybka 1.2 release) >2) New settings for adaptive search outlook >3) Some bug fixes > >Updates about Configurable Search Parameters > >The brief conclusions about Rybka search parameters to date are: > >1) The Seach Focus parameter seems to have little impact on playing strength >(oddly enough), and the default setting of 2 has indeed performed the best >overall (also quite odd, it was a wild guess on my part). >2) The Search Soundness parameter should either be "solid" or "ultrasolid". >Currently "ultrasolid" scores slightly better, but I'd like to collect more >data. The other two settings are now out of the running for default. >3) The Search Direction parameter will continue to have the "slightly >positional" default, which has performed slightly stronger than the >alternatives. >4) The Search Outlook parameter is very interesting and will now be investigated >in more detail. The potential for improvement is large, but a more properly >adaptive approach appears to be called for. > >Please see the section below for more details. > > >Search Outlook > >Background > >Of the parameters exposed for testing in the Beta 10 release, the Search Outlook >parameter has been the most productive. Under some conditions, optimistic >settings appear to give a marked improvement; under other conditions, neutral >and even pessimistic settings appear to be better. > >As a result, Beta 12 contains a greatly expanded set of configurable parameters >for playing around with this aspect of search. > >Disclaimer: these parameters are (at the moment) quite complicated, and if a >user doesn't know what he's doing, he can create some configurations which will >seriously harm the playing level of the engine. If you are not an expert in >these settings, I suggest that you leave them at their default settings until >more experienced testers have had a chance to determine which combination is the >best. > >Optimism and Pessimism > >The Rybka search has a concept of optimism and pessimism. To put this concept >into lay terms, a more optimistic search will look harder at alternatives for >the side to move which have been previously dismissed, while a more pessimistic >search will look harder at alternatives for the opponent. Inside the Rybka >search, these two concepts are already handled in a naturally asymmetric >manner, and this setting allows the user to control the extent of this >asymmetry. > >The practical effect is that optimistic settings are more likely to quickly find >resources for the side-to-move which increase the advantage, while pessimtic >settings are more likely to quickly find resources for the opponent which refute >the currently intended move (and force the player-to-move to look for a better >one). > >Adaptiveness of Optimism > >The initial data has suggested that a blanket optimism or pessimism is not the >best way. Rather, the search should be optimistic in some settings, and >pessimistic in others. Of course, this is done inside the search naturally. The >question for these settings is if we can make a global suggestion based on the >situation which is known before the search even begins. > >The following hypothesis currently exist: > >1) Weaker opponents call for more optimism >2) Good positions call for more optimism >3) Good positions call for more pessimism : >4) Improving positions call for more optimism >5) Fast time control games call for more pessimism > >As you can see, at least one of the above hypothesis is guaranteed to be wrong. >This investigation is in the early stages. > >A Bit More Technical > >The current implementation of the Search Outlook control is complicated enough >that I have to go a bit deeper. Rybka has an "iterative" search. That is, it >does a pass #1 of the root position, then a pass #2 (which takes longer and >comes to a better conclusion), then a pass #3, etc. Almost every engine works >iteratively, although the quantities being iterated over may differ. > >There is always a point where the engine is about to start pass #x of the >current position. This is the point at which we compute the level of optimism >for that pass (or "iteration"). At the next pass, we compute the level of >optimism again - it may be different. > >The optimism is calculated as follows: > >1) Start with the basic optimism value, according to the "Outlook" setting, >using the following translation: > >Very pessimistic: -2 >Slightly pessimistic: -1 >Neutral: 0 >Slightly optimistic: 1 >Very optimistic 2 > >2) Adjust the optimism based on the level of the opponent, taken from the >"Opponent Level" parameter. >(If "slightly strong" or "much stronger", we use the adaptation from the >"Stronger Opponent Adjustment" setting. If "slighty weaker" or "much weaker", we >use the adaptation from the "Weaker Opponent Setting". If "equal", we do not >adjust the optimism based on the level of the opponent.) > >An adaptation of "much more pessimistic" subtracts two from the optimism. >An adaptation of "slightly more pessimistic" subtracts one from the optimism >An adaptation of "none" does not change the optimism >An adaptation of "slightly more optimistic" adds one to the optimism >An adaptation of "much more optimistic" adds two to the optimism > >3) Adjust the optimism based on the latest search score for the position. This >is controlled via the "Good Position Adjustment" and "Bad Position Adjustment" >parameters. (A good position is considered one with a score of >20 centipawns, a >bad one is <-20 centipawns.) >4) Adjust the optimism based on the latest improvement of the position. This is >controlled via the "Improving Position Adjustment" and "Deteriorating Position >Adjustment" parameter. (A position is improving if twice in a row the search >score increased, or if the search score increased by >35 centipawns over the lat >three "iterations") >5) Adjust the optimism based on the time control. This is controlled via the >"Very Fast Time Control" parameter. (A time control is considered "very fast" if >the search allocates less than 8 seconds for the upcoming move.) > >The final optimism calculated using the above algorithm is used in the search >for that pass (or "iteration"). > >Search Parameters related to Outlook > >The following parameters are used to control the outlook (more details are found >in the "A Bit More Technical" section above.) > >1) Opponent Level >2) Outlook >3) Stronger Opponent Adjustment >4) Weaker Opponent Adjustment >5) Good Position Adjustment >6) Bad Position Adjustment >7) Improving Position Adjustment >8) Deteriorating Position Adjustment >9) Very Fast Time Control Adjustment > >Final Notes > >I have left the default configuration to be the "neutral" state, with no >adjustments. This is done to make sure that the default Rybka Beta 12 >configuration is well-tested before release. The hypotheses listed above must be >set by users manually. > >Other Configurable Search Parameters > >This section deals with configurable search parameters other than "Search >Outlook". These are at the moment a bit less important. > >Search Soundness > >Values: Ultrasolid, Solid, Speculative, Ultraspeculative >Default: Solid >Confidence in default: Medium to High >Overview: Similar in concept to "search focus". Solid values make fewer >assumptions about the position and are less likely to make a really serious >search mistake. Speculative values attempt to guess more. >Background: As in the case of "search focus", an intelligent search would use an >"ultraspeculative" approach. Unfortunately, Rybka's current heuristics don't >appear to justify it. Of the four values, probably the "ultrasolid" and "solid" >are the best choices at present. >Summary of Test Data: Ultrasolid and Solid are both candidates to be the default >setting in Rybka 1.2. Ultrasolid leads slightly, and my own intuition is quite >neutral between these two. The more speculative settings don't perform well and >they are now out of the running to be the default setting. > >Search Focus > >Values: #s from 1 to 6 >Default: 2 >Confidence in default: Medium to high >Overview: Small values instruct the search to emphasize searching broadly at the >expense of not searching as deeply. Larger values instruct the search to try to >look deeply, at the risk of overlooking (or underestimating) moves which are >improbable. >Background: I have been trying and trying to organize my search in such a way >that it can ignore looking at "stupid" variations and concentrate on the >important ones. Unfortunately, it has not been easy to do this. The heuristics >that I have come up with are controlled by this parameter. A value of 1 uses >these heuristics very modestly and continues to spend considerable resources >even on moves which are deemed unlikely, while a value of 6 uses them very >aggressively. The values of 1 and 6 are unlikely to be best. If I had to guess, >it would be that the modest settings of 2 or 3 are actually the strongest. >Summary of Test Data: The default has performed the best by a slightly margin, >but none of the other settings drops playing strength significantly. The >sligthly weird conclusion at the moment is that there is not much to gain by >twiddling with this parameter. > >Search Direction > >Values: Very Positional, Slightly Positional, Slightly Tactical, Very Tactical >Default: Slightly Positional >Confidence in default: High >Overview: Positional settings are more likely to find good quiet continuations, >tactical settings are more likely to find forcing continuations. >Background: Unlike the other parameters, this one controls the behavior of the >search "at the tips". The more tactical settings perform (or extend) additional >tactical investigations into tip positions. There are two types of >investigations: slightly positional is conservative is both, very tactical is >aggressive with both, while slightly positional is conservative with one and >aggressive with the other and slightly tactical is vice-versa. >Summary of Test Data: This setting has been included since the very first Beta >release and has been thoroughly tested. The original default was "very >positional", but slightly positional performed a bit better and I have since >aligned my thinking with the data :) The two tactical settings perform >noticeably worse than the two positional settings. > > >FAQ > >Is the Rybka search now complete? > >Yes - 100.0% complete for the Rybka 1.2 release. I am now satisfied that more >basic (and more time consuming) investigations are needed to continue this work >and that this is the right moment to stop. > >Which versions of Rybka feature playing strength improvements? > >Unfortunately testing has shown that the improvements in Beta 11 were minimal as >compared to Beta 10d, and the same applies to Beta 12. I do believe in these >changes, but facts are facts. Hence, existing Rybka versions have the following >three basic playing levels: > >1) Rybka Beta 1 through Rybka Beta 7 - same strength >2) Rybka Beta 9 - first of the search changes, first improvement in playing >strength >3) Rybka Beta 10, Rybka Beta 10d, Rybka Beta 11, Rybka Beta 12 - further search >changes and further improvement in playing strength > >What can we expect from Beta 13, and when can we expect it? > >Beta 13 should have the following features: > >1) EGTB access >2) Bug fixes > >It should be ready within 3 days. > >What about the actual endgame knowledge? > >This is being worked on in parallel and is going through an offline process. It >looks to be roughly on schedule for integration into a released version of Rybka >sometime around Feb 1. wow thank you Wayne
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