Ratings & Comments

Hello Greg,

How can I add evaluations for the maasai pawn pushes?

Sorry, but yellow X-es are captures!

I have an idea: you can turn Ox’s face to left in Stone Garden, as it was in my drawings, and make it different from Horizons. About Index it’s same. Please.

What’s happened with promotions rule? I hadn’t seen this yesterday. And what’s happened with Shielder? (maybe I can agree (or deny) capturing from front of Shielder, but it mustn’t push Shielders). It’s intentional or bug? Probably it’s bug, but I didn’t see this on small iPhone yesterday. Maybe earlier iPhone versions don’t support, and newer do? I hope it’s bug of rules.

Add "&submit=Edit" to the end of the URL, and this will open up the editor without running the code.

International Draughts is such a game: not only is capture mandatory, but you must capture the most chips that you can.

In Suicide only non-captures are FallBackLegality, and you never want to consider these in QS. So it is a moot point. (Note, however, that the champion Draughts program Scan does consider moves that invite capture in QS, and considers a position only quiet when there are no such moves, and no captures.) In Jumping there can be captures amongst the FallBackLegality. You must consider those in QS, but only when you actually have to fall back, of course. Always consider the highest non-empty class, and none other.

You have to assign a class to standing pat, to decide whether you can do that, and whether that would be higher class than de highest non-empty class amongst the captures. Usually this can be based on statistics. For Suicide and Jumping stand pat is always FallBackLegality. So no standing pat when there are legal captures. For Golem stand-pat will be legal. So no FallBackLegal captures.

What you want to consider in QS can very well depend on variant. Beside captures one usually considers promotions. In Shogi considering promotions for pieces already in the zone is counterproductive. Promotion is almost a certainty there, and the static eval can assume, say, 90% of the value. Most Chess programs consider non-capture check evasions.

I was thinking banning burning Fire Demons and Heavenly Tetrarches (possibly allowing it if something else is burned first), but allowing these pieces to be captured directly or via igui (the latter which is a locust capture). I tried doing it with the BadZone function used in the last version, and most of the time it worked perfectly, but for some reason the part testing for the evic parameter value would cause the area move (and sometimes non-capture moves) to disappear if two burning pieces were within burning distance of their orthogonal ranging moves. Right now, I am happy with the current version. Fire Demons can still be traded, but at least now it is easier for the moving Fire Demon to grab an additional piece without risking recapture thanks to the strengthened burning ability.

I am having problems with my new preset for Suzumu Shogi. For some reason, it just keeps echoing "Please report any bugs or errors to Adam DeWitt" over and over again instead of showing the preset like it should. Any help would be greatly appreciated.

I think you are making too much of this.

That is a disctinct possibility!  And that's why I wrote out all of that... so you could tell me if I'm on the wrong track, or overlooking the obvious.  I appreciate your time.  And, while I agree with what you've written, I'm not sure it justifies me doing anything differently.

You actually defined different classes of legality, and why stop at three? Generalizing this you could have an arbitrary number of such classes. I would prefer to call these 'priority classes'. You must play a move from the highest non-empty class.

Absolutely.  It did occur to me that one could invent a chess variant where there are even more tiers of legality...  But I'm not aware of any such game.  I've only come up with 3 instances of needing a middle ground between "legal" and "illegal".  I guess one could argue that as long as I'm making the change, I should go all the way and make an expandable hierarchy of legality.  But that seems more complicated and unnecessary.  And if it's not much more complicated, then it should be easy enough to adapt this should the need arise.  (And, while I would like to support as much as I reasonably can, it is not my goal to support anything that may come along.)

In Suicide captures are class 1, small in number, non-captures class 2, large in number. The situation that there would be a class-1 move we do not want to consider in QS, which would outlaw all moves we do want to consider, because these are all class 2, never can occur. Same with Jumping Chess; the unconsidered moves are by definition class 2. Of course QS is still affected, because if there are moves to be considered, there will be no stand pat.

I do not entirely understand this, but I think you are in agreement that "fallback legality" moves should be considered in qsearch in Giveaway and Jumping.

In Golem Chess typically all moves are class 1, and the occasional move that can be class 2 is even rare amongst captures. The logical thing to do, considering these statistics, is assume there will be class-1 moves amongst the non-captures.

I interpret this to mean that you agree that "fallback legality" moves should not be considered in qsearch in Golem Chess.

Note that the engine is very well capable of determining the distribution of moves over the various priority classes from nodes in the full-width part of the search. In particular you could make it keep track of how often there are no class-1 non-captures in the case there are no class-1 captures, and use that to decide whether to do a class-1 stand pat in QS.

Ok ... so if I understand correctly, your are not disputing that qsearch needs to be treated differently in Golem vs. Giveaway, but that, rather than a configurable variable that the programmer must set, the engine can determine this for itself.  Hopefully I got that correctly.  If so, my question is how much extra complication does this involve?  Certainly, I'd rather not add another user-configurable element if it's not necessary.  Heck, even the name of this hypothetical variable, "ConsiderFallbackLegalityMovesInQSearch", makes me a little embarassed.

Let's make sure I've isolated the questions to be decided correctly:

1. Do we need to expand beyond the standard determination of pseudo-legal moves as strictly legal or strictly illegal to account for games that have these types of "illegal unless there's nothing else" type moves?

2. If the answer to #1 is yes, do we just do as I've proposed and add a middle "fallback legality" category or do we go all the way and make a structure for any number of tiers of legality?

3. If the answer to #1 is "yes", regardless of the answer to #2, we have the issue of qsearch.  Do we have programmatic variables to determine what should be considered in qsearch, or do we determine that from statistical analysis?

Do I have this right?  And, if so, what are your answers to these questions?

I added H. G. Muller as an editor and made a note about our inactive editors.

It seems that the new move handler isn't updating the part of the diagram that shows which piece is selected.

I think you are making too much of this. For one, QS is never omniscient. The stand-pat assumption that the best non-capture will leave the evaluation approximately as it is, is just an assumption that is often false. There could be forks, or skewers. There could even be mate in one. Minimax turns out to be very resistant to random perturbation of a reasonably small fraction of the scores in the leaves; you must be very unlucky for such a perturbed score to affect the root score and move.

You actually defined different classes of legality, and why stop at three? Generalizing this you could have an arbitrary number of such classes. I would prefer to call these 'priority classes'. You must play a move from the highest non-empty class.

What to do is just a matter of statistics. How are the moves typically distributed over the classes, and how are the moves that typically change the evaluation distributed. In Suicide captures are class 1, small in number, non-captures class 2, large in number. The situation that there would be a class-1 move we do not want to consider in QS, which would outlaw all moves we do want to consider, because these are all class 2, never can occur. Same with Jumping Chess; the unconsidered moves are by definition class 2. Of course QS is still affected, because if there are moves to be considered, there will be no stand pat.

In Golem Chess typically all moves are class 1, and the occasional move that can be class 2 is even rare amongst captures. The logical thing to do, considering these statistics, is assume there will be class-1 moves amongst the non-captures. Unless you have reason to suspect there might be none. You would only be interested in knowing that if you did not find any class-1 captures, and when a lot of captures turned out to be illegal you could suspect that might be true for non-captures as well. (You know from the rules there cannot be any class-2 non-captures in Golem Chess.) Or you could simply know that you are in check, and that this is the reason for the large fraction of illegal moves. Especially if it is a contact check, for which the only legal non-captures can be King moves. But then you would probably extend even in QS, and the problem disappears. Otherwise you assume there will be legal non-captures, and guess their score as the current evaluation, to stand pat. It is what you always do when not in check, and the fact that there was only a capture that was discarded because it wasn't class 1 doesn't do more damage than that there occasionally is a class-1 non-capture that would score far higher than the current evaluation.

Note that the engine is very well capable of determining the distribution of moves over the various priority classes from nodes in the full-width part of the search. In particular you could make it keep track of how often there are no class-1 non-captures in the case there are no class-1 captures, and use that to decide whether to do a class-1 stand pat in QS. If there are more priority classes you would want to know what typically the highest-class non-capture is, given the highest-class capture that is available. If that is lower or equal to that of the highest-class capture, the capture can be searched, and a stand pat of the assumed highest-class non-capture can be tried only if that belongs in the same class.

The page for Tigrey has now been published

I already knew that the author disagrees with me when he qualifies his board of "ridiculous". In fact that's the point as I was indeed saying that this board is not "ridiculous" imo. Second, I do not mean at all this game should be published. I completely share Fergus's opinion and your opinion on this. I was just discussing that maybe some interesting games could be imagined on such a board. No more.

..., but the current version of the diagram does not have the tools needed to do that.

I don't know exactly what you have in mind, but it sounds like an antitrade option to specify relative ironhood for a group of piece types for locust-capture only would do it. This would not be hard to implement; just exempt the replacement capture from one of the existing options.

Could we get some info on how the non-FIDE pieces move? Thanks.

This is a technical follow-up to recent discussion in other threads.  Overview: there are cases where whether a move is legal depends on what other moves are available.  These follow the general pattern where a certain class of moves are only legal if there is nothing else that is legal, in which case this class of moves all become legal.

I originally raised this in response to the Golem Chess rule that "a Golem or Half-Golem may not capture an opposing Golem or Half-Golem if the opposing Golem or Half-Golem is two squares away and defended by a piece on its own side" ... UNLESS there is no other legal move.  I then realised this was similar to the Losing/Giveaway Chess rule that non-capturing moves are only legal if there are no captures.  We discussed a plan for implementation, which I have started implementing.  While doing this, I found a place in ChessV where I had already encountered this problem and "hacked" it in a less general way and forgot about it ...  That is the Jumping Chess rule that if there is a piece on an edge square that can make a capture, the player must make one of those moves (their choice) but nothing else is legal.  Having come up with these three cases already, I must assume there are more.  So, on to how these can be solved in a universal chess engine ...

Typically, moves are either legal or not.  It is true that a move generator generates so-called "pseduo-legal" moves they might turn out not to be legal when made (if, for example, they expose your King to check or leave him in check.)  But when these pseudo-legal moves that are not really legal are actually made, it is detected that they aren't actually legal and they are skipped.  Details of how this happens varies but it doesn't really matter.  This is simple and doesn't depend on any other moves.  ChessV handles it like this: whenever a move is made, a MoveBeingMade message is routed to every Rule in the Game that receives that message.  The rule can then return an IllegalMove result code to rule the move illegal.  Besides exposing your King to check, other reasons exist such as a LocationRestrictionRule stopping your King from leaving the castle or your Elephant from crossing the river, or the TradePreventionRule making Lion "iron" by preventing captures after you've captured the opponent's Lion.  (As an irrelevant aside, MoveBeingMade messages are also handled just for the purpose of updating game state - such as the EnPassantRule determing when a pawn push creates the possibility of an en passant capture.)

But now we have pseudo-legal moves who's legality depends on what other legal moves exist.  This presents a new challenge.  The general idea is this: allow the MoveBeingMade function to return a new code, which I originally called IllegalUnlessOnly but am now calling FallbackLegality.  Moves of FallbackLegality are all legal if and only if all pseudo-legal moves are either FallbackLegaltity or IllegalMove.  These moves could be temporarily set aside and tried again later if appropriate, or, if appropriate, a new node could be launched with tail recursion wherein FallbackLegality moves would be accepted.  For purposes of this discussion, the implemention details don't matter.

So now that I'm actually implementing this, of course I've found an issue - which is the reason for this post.  What we have so far is straight-forward ... until we get to Quiescent Search.  I won't define QSeach in detail since I've explained it several times before, and since this conversation is only really of interest to implementers of chess variant engines who should know this anyway.  But in qsearch we only try captures so we don't actually know what all the legal moves are.  For purposes of determining the impact of this issue, a quick revisit of the three known use cases of FallbackLegality:

1. Losing/Giveaway Chess: If a player can make a capture, he must (although he can choose which).  So all moves which are not captures are FallbackLegality.

2. Jumping Chess: If a player can make a capture with a piece that is on a boarder square, he must (although he can choose which).  So all moves which are not captures of a pice on a border square are FallbackLegality.

3. Golem Chess: a Golem or Half-Golem may not capture an opposing Golem or Half-Golem if the opposing Golem or Half-Golem is two squares away and defended unless there is no other legal move.

Impact on qsearch?  For cases 1 and 2, I think there is no impact.  These rules already consider everything that is not a capture to be of FallbackLegality.  Easy peasy.  But #3 is a problem.  Here a capture can be ruled illegal if there is a legal non-capture, which we won't know in quiescent search.  We could generate and test them all, but that would be way, way too expensive.  (Something like 90% of nodes are qsearch nodes.)  So, if we treat this case like 1 and 2 and sweep it under the rug, we can consider a golem capture of the enemy golum legal when it is not.  This could have a dramatic impact on the score.  So I think we should not consider this capture in qsearch, since the circumstances where it would be legal are quite rare.

We could rule out all FallbackLegality moves in qsearch ... That would not affect case #1 at all and it is what we want in case #3, but it would be bad in case #2.  In case #2, we want to do exactly what we normally do - generate all captures and use our normal rules for FallbackLegality.

I think this is solved by adding another Game variable.  As I have variables for things like whether Static Exchange Evaluation should be enabled, I plan to add a Game variable called "ConsiderFallbackLegalityMovesInQSearch" to control whether normal rules for FallbackLegality should be applied in qsearch or if we should just rule all these moves out.  In case #1, the setting wouldn't matter.  In case #2, we would want the setting to be true.  In case #3, we would want the setting to be false. (This will result in an incorrect evaluation on occasion, but qsearch isn't perfect.  This is the lesser of the two evils.)

Mitsugumi Shogi is ready

I have finalized the double burning version of Suzumu Shogi, and by extension, Mitsugumi Shogi. I might reintroduce the ban on burning pieces with burning moves in the future, but the current version of the diagram does not have the tools needed to do that.

The GC presets are no longer up to date.

The idea of an infinite dimension on the board is interesting in my opinion.

That may be, but that is not what is described here.

Ridiculous means deserving mockery or being absurd. It is none of them.

Even the author disgrees with you.  The page is entitled "Chess On A Ridiculously Long Board".

The game we have here is not good as only Rooks and Queens can cross it

I would consider that a pretty significant problem.  I agree with Fergus' conclusion.  There are already at least two viable infinte variants on this site, and there may be room for the invention of others, but this page - as it stands - will not be published.

Maybe the grammar it's part of the fun in that game :=)

Looks like it's above all a matter of punctuation.

"the knight can when it take make (with that same knight) another move the bishop can not be taken but the bishop can also not capture other pieces"

I would translate into:

The Knight can make a second move when it captures at its first move. The Bishop cannot be captured and cannot capture.

Remarks: It is not said if the 2nd move of the Knight can be a capture. If yes, can it continue and make a 3rd move (or capture and etc.)?

The Bishop looks like an obstacle that can be moved.

Nice.