[ Help | Earliest Comments | Latest Comments ][ List All Subjects of Discussion | Create New Subject of Discussion ][ List Latest Comments Only For Pages | Games | Rated Pages | Rated Games | Subjects of Discussion ]Comments/Ratings for a Single Item Later ⇩Reverse Order⇧ Earlier⇩ Earliest⇧ Sac Chess. Game with 60 pieces. (10x10, Cells: 100) [All Comments] [Add Comment or Rating]Kevin Pacey wrote on 2017-06-19 UTC Hi Fergus Yes, 3-fold repetition is a draw in Sac Chess. I had assumed (apparently incorrectly) that somehow by the form to enter a submission on CVP, and by some instances I looked at of other submitted variants that have been played, that a submitted variant has the same basic or auxilary rules as standard chess, unless otherwise stated by the inventor, at least if the variant seems clearly intended to be chess-like (Shogi & Chinese Chess variants for example, would be another story). Thus, by another rule of standard chess, Sac Chess would also have agreed draws allowed (which Game Courier assumes for all variants), and also the 50 move rule that is used in chess (with some modern exceptions that make the rule to be for 100 moves instead according to FIDE, e.g. R+B+K vs. R+K, and many semi-specified positions with 2N+K vs.P+K, the latter of which, however, clearly couldn't be applied to Sac Chess' 10x10 board). I was actually wondering recently if the 50 move rule should be applied to larger board variants than 8x8, since even B+N+K vs. K might take more than 50 moves in the worse case with good play on 10x10, though I doubt it will in that particular basic endgame, or others that might arise in Sac Chess. In general it's a bit tedious for inventors to try to cope with or unfailingly anticipate every little rule case that might come up. A solution could be simply to state in one of one's CVP submissions that the basic rules of chess apply unless otherwise stated, but that might have caused some confusion in the case of Sac Chess, as you can see from the above rule cases, if I didn't still take the trouble to elaborate at length on them as I have above. I'd say if any variant ever becomes popular enough, any future governing body it would have (like FIDE is to chess) might later fine-tune the rules or clarify rule omissions/ambiguities made by the inventor. At least on Game Courier, the players afaik seem to sort out such rule issues without much trouble, or perhaps even consult the inventor as here. I would observe that some variant submissions, even of old variants that might even be played on Game Courier, have an author's comment that certain rules aren't made clear by the inventor, and in such cases iany rule enforcing preset programmers can decide on the exact rules they enforce in their presets. I don't know if Carlos took into account any of the rule cases (3 fold draw, 50 move rule) that I discussed at length above as they apply to the Sac Chess rule-enforcing preset that you're currently using, but if you care to you might assume for now he did not. On a personal note, I'd intended to stop playing on Game Courier for at least the summer (if not longer) due to, not least, having no air conditioner (just a fan) in the room where my 'playstation' is in my small apartment, but I'm now looking into the chance of having an affordable and practical portable air conditioner. Kevin Fergus Duniho wrote on 2017-06-19 UTCIs 3-times repetition a draw? That's what I'm presently going for in a game I'm playing. Kevin Pacey wrote on 2017-04-29 UTCHere's a Sac Chess game I played vs. Carlos arguably not so long ago. It seems like the closest Sac Chess game played between people that I've seen to date. Perhaps it's a matter of taste, but I like that of the relatively few pieces left on the board at the end, all of the 4 Amazons still remain: /play/pbm/play.php?game=Sac%2520Chess&log=panther-sissa-2016-289-852 Kevin Pacey wrote on 2017-03-27 UTCAfter some playtesting of Sac Chess, I am more confident it is playable, and may be a very rich game indeed, given it has so many pieces. What pleases me a lot is that while in chess an average game is 40 moves, with a pair of units traded on average every 5 moves (thus leaving an average of 8 pieces per side at the end of a game), in Sac Chess an average game so far on Game Courier seems to last about 60-80 moves, though at times being played out until mate (if done for chess, an average game of it might last about as long, too). It seems the rate at which a pair of units is traded in Sac Chess is about every 3.5 to 4 moves, which would also put an average game at around 80 moves, if such a game got down to 8 pieces per side (though it doesn't seem to get this far in practice, so far on Game Courier). Another nice thing about Sac Chess is that it seems to allow for more decisive games than is the case in chess, if played at a high level, I'd guess. One thing I'm not sure about is how rich the early opening phase, or range of 'good' opening variations, can be for Sac Chess. Playing something like the Pirc Defence in chess seems less attractive here, since White's Queen is guarded by an Amazon in the start position, so White might early on hit Black's knight on the kingside with the appropriate centre pawn. Also, Open Sicilians in chess may be a little, or a lot, less attractive for White in Sac Chess. Then there are the ramifications of the Queen's Gambit Accepted in chess still waiting to be analyzed, if played in Sac Chess, and this could be really critical to the range of attractive/promising White openings. On the other hand, 'insipid' sidelines in chess may be much more interesting in Sac Chess (in regard to the early opening moves, I mean as always here). Even if White's initiative is less than in chess, this can be seen as a good thing, perhaps. Regarding the names I chose for some of the pieces, I still like 'Missionary' and 'Sailor' as used (these seem even a bit appropriate, given what a man is crossed with, e.g. a bishop in the former case). However, I have some regret about not using 'Centaur' instead of 'Judge' (I somehow missed the Centaur entry on wikipedia, in spite of looking at its long list of fairy chess pieces several times for just such a precedent). On the other hand, maybe there's something nicer about using the name of a human occupation (Judge), rather than the name of a mythical monster; at least there were travelling judges in medieval times. Plus, I'd note that I don't completely get the consistency of why, e.g., an Amazon is called what it is, since no horse is involved in that name, and given that such a female warrior doesn't necessarily ride a horse (not only that, but a knight might be seen as a man riding a horse). But I digress. Kevin Pacey wrote on 2016-07-14 UTCCarlos wrote some months ago: "I have just played a game versus the HG's Fairy-Max/Winboard/Sac Chess program..." I have a question for HG: I wasn't aware till I searched recently that Fairy-Max has its own page on the web. Is Sac Chess one of the variant programs under Fairy-Max that any viewer/user can find available even nowadays? Maybe I didn't look hard enough, but I didn't see Sac Chess listed as such. Thanks in advance, Kevin. P.S. I saw after making this post that you mentioned your Fairy-Max program for Sac Chess on Chess.com 4 months ago. Thanks for that, too! Kevin Pacey wrote on 2016-02-03 UTCI've adjusted my tentative Sac Chess relative piece value estimates, in just a few cases, after realizing that I had overestimated the fighting value of a Sac Chess K. Carlos Cetina wrote on 2016-01-31 UTCI have just played a game versus the HG's Fairy-Max/Winboard/Sac Chess program and translated it to a Game Courier log. Watch it here. Everyone draw their own conclusions. [Play Tester played the role of the program.] Kevin Pacey wrote on 2016-01-31 UTCI thought that tonight I better try unzipping that link you provided, H.G., in case I needed my sister-in-law's help tomorrow. It was pretty much as simple to unzip as you described in an earlier post. The only thing was I couldn't seem to save it as anything but a temporary download, so I'll have to download it each time I use it, unless I can figure out how not to. My used laptop was a gift from a friend, which might somehow complicate things due to any possible security measures set for him. The program was set for 1 minute per side, and I initially tried playing at that speed. I clearly blundered a pawn for nothing very early, but for some reason the engine passed it up. Some more blunders followed (by me) and I soon allowed a mate. The next three games I tried 5 minutes, then 10, then 15. At one point I noticed I had lost on time, but was allowed to keep playing anyway (I didn't bother to figure out how to change that yet, if I wish to). Each of these 3 games I lost as well. Maybe I'm not yet used to the images for all the piece types, but the odd blunder (or once a mouse slip) kept occurring. I came closest to doing well in the 15 minute game (I always tried not to 'lose on time'). After that I set the program to have two engines play a 15 minute game. Again they each exceeded the limit and were awarded a further 15 minutes each on the clock all the same. As a spectator I thought the engines played conservatively, if not anti-positionally (IMHO). At one point Black seemed to go ahead in material considerably after about 40 moves with one trade only. Then trades came thick and fast, and eventually Black won a pawn ending two clean pawns ahead. The game only took about 80 moves (until mate), which would be about right for standard chess. Thanks again for the link, H.G. Kevin Pacey wrote on 2016-01-31 UTCSorry H.G., I hadn't been in a hurry up till now, and didn't realize you were eager. I wanted to at least see how my 2 games with Carlos were going to develop before getting more adventurous by playing a computer. Looking at our game of Sac Chess, Carlos seems to be doing very well, which doesn't suggest my chances would be good against a program (against a good one, I half expected to score say 1/4, if it would be about 200 rating points higher than my standard chess rating). In the meantime, it is becoming more clear to me that looking for a computer-resistant chess variant is a futile exercise, especially now that 19x19 Go computer programs are demonstrably so much stronger than before. I had guessed that it might take up to 100 more years for Go programs to take over and eventually dominate that game, from people. I also had wanted to try to see my Glinski's Hexagonal Chess game with Carlos to a conclusion, before trying out that link you gave. An irrational concern that I might somehow go wrong and mess up my laptop in some way, before that game had finished, had been with me. Anyway, I'll try to get playing that computer program at Sac Chess soon after my brother & his wife go home tomorrow. H. G. Muller wrote on 2016-01-30 UTCDid you already have an opportunity to try the program at <a href="http://hgm.nubati.net/SacChess.zip">http://hgm.nubati.net/SacChess.zip</a> ? Kevin Pacey wrote on 2016-01-30 UTCI've added the following to the end of the Notes section for my Sac Chess submission (to try to, in the most natural way I can imagine to date, accommodate those who dislike there being a single queen and two amazons in the setup position for Sac Chess): "Note: to accommodate those who dislike the queen being clearly inferior to amazons both in their power AND in their number in Sac Chess at the start of a game, I can suggest the following fairly natural idea for a modified variant ('Royal Bevy Chess'), i.e. it has a similar setup and the same rules as for Sac Chess. Namely, in the setup position for Sac Chess, switch 2 queens for the 2 amazons, and switch an amazon for the single queen. This idea of having two queens and one amazon in a setup position may have first been used in 'Alekhine Chess', which is somewhat similar to Sac Chess, perhaps; here's a link to it:" http://www.chessvariants.com/index/external.php?itemid=zAlekhineChess Kevin Pacey wrote on 2016-01-26 UTCI originally had in mind that the person I seem to recall who disagreed with the game produced by the inventor of Alekhine Chess (as far as the number of its Amazons to be included) was an example of a person not pleased with a particular game (other than mine, which is somewhat similar to Alekhine Chess). Clearly not everyone can always be satisfied with any particular variant, and someone may want it altered even in an unspecified way. In Sac Chess, if one has a position on the board with all piece types included, such as in the Setup position, the Amazon is the only piece that can always (unless pinned to the King) take any sort of piece type that is threatening it (I think this is a major point that you're indicating). The game is also a bit heavy on pieces that can move at the least like both a king and a rook (or bishop), e.g. both Sailors, both Amazons, and the Queen (for each side) can move like a king or rook, at a minimum. It's a drawback (of the theme of compound pieces that I used), possibly. Whether or not it would be better to alter the game is an open question, but at this stage it's already being played on Game Courier, and I think I like the way it's turned out so far. Perhaps I (or someone else) can make a variant based on Sac Chess at a later date that may prove popular. At the moment it's the only variant I've invented (out of 10, so far) that someone (namely Carlos) kindly decided to write a Game Courier program for. [edit 28 March 2018: I'd note, too, that, e.g., in the historic variant Courier Chess, the queen used there is a ferz-like piece, clearly inferior in powers to the guard-like piece type that is also used in that game, so it seems that Sac Chess is in such a way at least not without one or more precedent(s), in variant(s) that proved at the least somewhat popular in the past, if only regionally perhaps.] John Whelan wrote on 2016-01-26 UTCRe: "you can't please everyone" - No, but it is not as though I ever demanded you do 1 Amazon & 2 queens. It was 1 of several alternative suggestions. And these were merely examples to suggest that the issue is not insoluble. Re: "close to standard chess in spirit". Seems to me the pieces of FIDE chess have a high degree of ability to threaten each other without being threatened back. Even the Queen, the most powerful piece on the board, can be threatened by the 2 knights. Seems to me a lot of that is lacking here, for all the variety of pieces. If an opposing piece cannot threaten you back, it is probably less powerful. Kevin Pacey wrote on 2016-01-26 UTCFwiw, here's a link to Alekhine Chess, which uses 1 Amazon and 2 Queens: http://www.chessvariants.com/index/external.php?itemid=zAlekhineChess Also fwiw, I seem to recall somewhere one person commented that that game could be better with 2 Amazons and 1 Queen, so as to lessen the chance that all the Amazons might be traded off... you can't please everybody. I wanted to keep Sac Chess fairly close to standard chess in spirit, in a way I hope that's understandable, when adding all the compound pieces to fill in the spaces in each side's camp, on a 10x10 board. Including Amazons in a variant always seems to create some sort of a backlash eventually, but I couldn't resist doing so since they seemed a natural extension of the compounds that I used (which are all the crowned or knighted standard chess pieces). John Whelan wrote on 2016-01-26 UTCOne solution would be to have two Queens, and to put the Amazon in the place of honor next to the King (and perhaps change their names). The only thing stopping this would be a desire to keep both the traditional names, and their traditional significance. Another solution might be to give the King some kind of enhanced movement power while the Queen is in play, such as an ability to switch places with the Queen, or an ability to jump over a Queen. Another solution might be to give all the knight-combo pieces, including the Amazon, limited range: 2 or 3 squares (distinguishing them from the King-combo pieces). This would leaving the Queen, Bishop and Rook as the only full-range pieces. This would leave most of the pieces geographically localized, which fits the advice of some who have discussed computer resistant variants. There are any number of possible solutions. Kevin Pacey wrote on 2016-01-23 UTCIn my submission I gave links from my Chess Federation of Canada website blog, including my entry there that covered Sac Chess in detail. Included in that entry was my proposal for two slight spinoff variants of Sac Chess to accomodate anyone who dislikes Amazons being clearly more powerful than a Queen. One spinoff variant ("Cash Chess") had two different piece compound pieces replacing each of the 2 Amazons in both camps. These were to be B+N+K ("Freemason") and R+N+K ("Ship") compounds, each a compound piece of my own invention (afaik). I wasn't keen on this spinoff variant myself, since there would be less near-symmetry in each camp, and there would be more piece types to remember in total. The other spinoff variant ("Royal Sac Chess") would let Queens have a small distinction over Amazons on at least some occasions. In this spinoff variant, in the event of stalemate or a three-fold repetition of moves (perpetual check being a case of such), if one side had more queens on the board than his opponent then he would win the game, else it would be a draw in the event of an equal number of queens. I kind of liked this spinoff variant, as perhaps an important way to justify having Queens on the board alongside Amazons (which are clearly superior in their relative value AND movement capabilities on an empty board). On the other hand, it's using a rather artificial rule change that would drastically affect some games' final results. In the end, I decided that the reasons you gave for liking having a Queen, besides Amazons, were adequate enough, such as keeping a quaint royal tradition going in spite of my wanting to include many compound pieces in Sac Chess, including Amazons. The Amazon seems to get a bad rap because it is so powerful (it can mate a King on an empty board with no assistance, for instance). At least having a Queen on the board as a possible threat to trade itself for an Amazon gives a player with an Amazon one more thing to watch out for. John Whelan wrote on 2016-01-23 UTCI am interested this variant because I am fascinated by large chess variants, and this variant is LARGE (Dragonchess beats it though). One thing bothers me, though. The Queen. She retains her status as the only unique piece other than the King. She retains her place of honor by the King's side. But there is nothing special about her in this version. She is trumped to two Amazons, and a number of other pieces come close to her in value. H. G. Muller wrote on 2015-12-21 UTC> <i>https://en.wikipedia.org/wiki/Princess_(chess)#Value</i> <p> And guess who wrote that there! :-) <p> Note that arguments based on move counting on an empty board are often unreliable. Distant slider moves contribute very little to value, because during most of the game you will not be able to make them anyway due to blocking or board edges. And once the board population has dropped to where you can, they often lead to places where you have no business going anyway. In defending KRPKR it hardly matters how far away you can move the Rook from where the Pawn is. <p> The value of a piece is mostly determined by how efficiently a piece supports and combats Pawns in the end-game. <p> Another factor could be 'winning power' in often occurring Pawnless end-games, which determine how easily you can draw by acrificing a piece for the opponent's last Pawn to stop its promotion. E.g. Queen + minor (B or N) vs Queen is draw, making Q+minor+Pawn vs Q+minor also easy to draw. But Q+minor vs Chanchellor or Archbishop is a win. Q vs R is virtually always won, giving Q+P vs 2R a big advantage, but C vs R is only won if your King is not confined to its own board half by the Rook, and A vs R is a dead draw, making A+P vs 2R a hopeless proposition. More or less coincidental properties like that might have impact on the value, although it is different to separate cause from consequence here:one could also argue that some pieces win and others not against a given opposition is because they were generally inferior. That it is not possible to checkmate a bare King with a pair of Knights, but you can do it with a pair of Phoenixes, does not seem to be tracable to general inferiority of the Knight, however. (E.g. KRKN is generally a draw, but Rook vs Phoenix is a general win.) Kevin Pacey wrote on 2015-12-20 UTCThought I'd give the wikipedia link below, discussing the value of the Archbishop (Princess) fairy chess piece: https://en.wikipedia.org/wiki/Princess_(chess)#Value I'd note wikipedia mentions that computer self-play studies were used to establish a sort of value for this piece that Muller gave (though he nor anyone else seems to be credited for the computer studies, as far as I've read). Note also that links concerning the Chancellor (Empress) and Amazon are given by wikipedia. Regardless of arguments about what the Archbishop's value might be in a particular chess variant, I'd note that wikipedia mentions that the computer studies led to the conclusion that the Archbishop increased its relative value (in comparison to that of a queen) on an 8x10 board, as opposed to the smaller 8x8 board. Without bringing in any notion of synergy necessarily, I can give one possible reason (or contributing reason) why that conclusion might be correct, in case no one has mentioned it. Namely, whereas on an 8x10 board the rook component of a queen benefits the queen as a piece by 2 extra squares covered (on an empty board) at all times, not depending at all on the location of the square, note that the knight component of the Archbishop has many more available squares to it (than on an 8x8 board) where it benefits the Archbishop as a piece, by up to 4 extra squares covered more than from a less favourable square nearby that a knight might have to settle for on the smaller 8x8 board. I can note that on a 10x10 board (such as for Sac Chess), the rook component for a queen would by similar reasoning pick up 4 extra squares covered on an empty board (than if on an 8x8 board) whereas the knight component for an Archbishop often allows it to pick up up to (still) just 4 extra squares coverage for the Archbishop (than if on an 8x8 board), suggesting to me that a 10x10 board might not benefit an Archbishop like an 8x10 board apparently did, in terms of its value to that of a Queen. Perhaps inconclusive and murky pondering on my part, I'll admit, but it gave me pause. Kevin Pacey wrote on 2015-12-19 UTCH.G. wrote: "BTW, did you just place the text string the generator gave you in a non-HTML submission, or did you have to tick 'Using HTML tags' to make it accept the diagram?" Being tech-challenged these days, my attempt to describe what I did would be: I went to edit my Sac Chess submission, then in doing so noticed that just above the 'Setup' box (i.e. to show the starting position for a chess variant) there now exists a sentence that mentions the Diagram Designer. I then clicked (on its blue highlighted words) "Diagram Designer" and a new window opened up, i.e. that of the Diagram Designer. Perhaps it wasn't quite obvious to a newbie how to use it even in a minimal way, but its board shape setting happened to be for a "Square" shape (since the Diagram Designer by default was for standard chess). I tried setting "Columns" = 10 and the square board increased from 8x8 to 10x10, still showing the 32 chess pieces. I happened to decide to click on some hignlighted words for a setting ("Next Rank", I think), and revealed to me by a new window was a long documentation. This was actually useful enough to me in a way (with my minimal desire, i.e. to at least initially find any possible quick & dirty way to make a better diagram for my Sac Chess submission), because it finally dawned on me that the 26 characters of the alphabet each represent an available chess or fairy piece type in the given set (abstract pieces), and a character is to be used as part of the FEN string. After closing this window, I saw that the FEN string default was indeed for chess, and I could quickly tell how to use the FEN string for Sac Chess pieces (and its empty squares) instead. The slight difficulty after that was deciding which letters of the alphabet corresponded to desired Sac Chess pieces, though I eventually decided to use the standard chess piece abstract figures as a sort of theme I carried over when I decided on the letters of the alphabet to represent other (fairy chess) pieces in Sac Chess in the FEN string. At any time I could click on an "Update" button and the Diagram Designer would show the latest version of the board, with the pieces on it. When I had finished, I knew there was a box in the Diagram Designer that contains a brief code (it described it as HTML code), and the final code corresponded to the work I had done with the Diagram Designer. The instructions above this box said to simply copy the contents of the box to my Chess Variants webpage, so I copied the contents as the first step of a quick cut & paste. I closed the Diagram Designer window, i.e. returning to my submission webpage that I was editing. I then did the pasting of the Diagram Designer code into the "Setup" box of my submission webpage, which simply showed the text of the code as a result (I had before now deleted my old version of a Setup diagram that wasn't up to snuff). After I submitted this edited version of my Sac Chess submission, now whenever I look at the new version of it, the Diagram Designer diagram I specified actually shows up on my screen. Edit: I've identified the squares pieces are on (by text) in my Sac Chess setup diagram now. Fergus Duniho wrote on 2015-12-19 UTCAbstract is a good choice for the piece set, though I'm biased. I will mention that three of the pieces you chose (besides the King) were designed as royal pieces for games with alternate royal pieces (mainly Fusion Chess and Cavalier Chess). The one that could most easily be confused for a royal piece is the one combining the King and Knight images. There is a nonroyal alternative that combines the Man and the Knight. This is called ct in the Abstract: All set. I'll add some non-royal alternatives for the others later. Another thing that is important is to make a connection between the diagram and your descriptions. Including an image of each piece in the piece descriptions is a good way to do this. An alternate way to do this is to mention which spaces each piece starts on. H. G. Muller wrote on 2015-12-19 UTC> <i>Please confirm I've used all of the right types of figures to represent all of the pieces and pawns in the diagram, as I was slightly uncertain what some of the figures represented</i> <p> It seems you did. But, because of the uncertainty you express here yourself, do you really think this is the best image set to represent Sac Chess? To me the Alfaerie images are a lot more recognizable. Under 'Compounds' the Diagram Generator seems to have symbols for all the pieces in your game, including the BK and RK compounds. <p> One problem now is that the part where you explain how the pieces move you refer to them by ID letter, but the IDs are no longer part of the diagram. Perhaps you should prefix those explanation lines by a list of squares on which these pieces start, so people can make the connection between image and name. <p> BTW, did you just place the text string the generator gave you in a non-HTML submission, or did you have to tick 'Using HTML tags' to make it accept the diagram? H. G. Muller wrote on 2015-12-19 UTC> <i>For example, if one incorrectly sets the value of a rook (or, I would opine for argument's sake, even a bishop) exactly equal to the value of a knight, I'd imagine in a number of playtest games the side with an extra rook would erroneously trade it for the extra knight of the opposing side, say when thinking the position was approximately equal in all respects.</i> <p> Indeed, this is exactly what happens. The Rook side will needlessly squander a Rook for a Knight, and because the initial setup was likely to give the already two Pawns worth of compensation, would badly lose after that. So making the programs erroneously believe that a certain trade is equal is one of the major pitfals of this method. This especially holds for 1-on-1 trades, as opportunities for concerted multiple trading do not occur very frequently. The worst of those is if two values differ exactly a Pawn, as Pawns are abundant, and X + Pawn for Y opportunities are not so rare as the others. <p> But you know which values have been given to the pieces in the opponent armies, so you know which of those are close to the initial estimate of the value or one Pawn above/below it. And then I usually try to stay ~20cP away from those points. If needed you can make two test runs, one with a programmed value 20cP above what you think it should be, one 20cP below it. If the results are nearly equal there is no reason to distrust it. If they are different the one that used the programmed value closest to what the score outcome suggests will obviously be the more reliable, and if the programmed value is different from the score-outcome value, you repeat the test with the latter. If the value suggested by the score is very close to that of a piece in the opponent value, you can repeat the test against armies of another composition, lacking the offending piece. It is always better to base the value assignment not on a single imbalance, but on a variety of imbalances anyway. (E.g. not only play A vs Q and A+P vs Q, but also A+P vs 2R, A+P vs 2N+B and A vs R+N+P.) <p> > <i>Regarding when a preliminary value is assigned to an Archbishop that is at least slightly different than that of a Queen when pitting the two pieces against each other in playtesting (other material being equal at the start), ...</i> <p> Well, obviously predicting the desirability of some trades the wrong way around will lead to unnatural play, which might affect the statistics of other trading opportunities compared to 'natural' games, which then affects the outcome. This is all possible in theory. In practice, however, you will be able to see that when it happens. This is why pondering about it is not the same as actually doing it. You can repeat the test with all kind of different programmed values for A, and see how the result score varies by this. If it doesn't vary at all, <i>apparently</i> the problem does not occur in practice. And in the worst case the value implied by the scores does significantly depend in some way on the programmed value, and you have to search for self-consistency, i.e. the value you have to program to get the same value out of the score. <p> With the usual resolution I am aiming for (~0.2 Pawn), however, I have never seen that happen, though. Trying to get more precise values is probably meaningless, as you will start to resolve all the higer-order corrections to the model of additive piece values. E.g. some pieces might do better against Knights, other might do better against Bishops. Kevin Pacey wrote on 2015-12-19 UTCI've changed the setup position diagram for my Sac Chess submission, using the Diagram Designer as you requested, Fergus. Please confirm I've used all of the right types of figures to represent all of the pieces and pawns in the diagram, as I was slightly uncertain what some of the figures represented (some of the 26 possibilities to chose from were mysteries to me, but I thought I found all of the ones applicable to Sac Chess). Eventually I'll redo diagrams in similar fashion where needed for all of my Chess Variants Pages submissions if I am able to figure out how to. Kevin Pacey wrote on 2015-12-19 UTCH.G. wrote: "...One would expect the playtest to be only meaningful when the values used are consistent, i.e. the programmed value used for deciding on trades are the same as the value that comes out based on the score percentage. But to my surprise, putting a moderately wrong value there hardly had any effect on the outcome at all. If I put Q=9.5 and C=9, and play an army with Q against an army with C, the Queen wins by ~58%. If I put Q=9.5, and C=10, the Queen still wins by 58%! The explanation is that both engines share the misconception. So one of the two sides will always try to avoid the trade, meaning that Q for C trades will be relatively rare. So the test mainly measures how much damage Q and C do to the other pieces. Although a wrong C value might lead to wrong 2-for-1 or 3-for-1 trades, the number of occasions where such a trade can be forced is relatively rare, especially if they are not exactly equal, so that one of the players will try to avoid them. So the most error-prone value assignment is actually the one where the value is exactly the same as that of another piece, or the sum of two other pieces (and wrongly so). So I usually avoid that. ..." Fwiw, instances of assigning a preliminary value for a piece to the same value of that of another piece (and also being a wrong preliminary value) were in fact uppermost in my mind. For example, if one incorrectly sets the value of a rook (or, I would opine for argument's sake, even a bishop) exactly equal to the value of a knight, I'd imagine in a number of playtest games the side with an extra rook would erroneously trade it for the extra knight of the opposing side, say when thinking the position was approximately equal in all respects. If the number of such games is significantly large in the playtesting, this could seriously drive up the percentage of drawn games (let alone losses) in such games where a rook for knight advantage is erroneously thrown away through such a trade, substantially skewing the results of the playtesting. Regarding when a preliminary value is assigned to an Archbishop that is at least slightly different than that of a Queen when pitting the two pieces against each other in playtesting (other material being equal at the start), for example, and the value assigned the Archbishop is at least slightly wrong, I am now wondering something similar to what was uppermost on my mind before. That is, if the effect of all resulting incorrectly avoided trades during playtesting (e.g. of Queen for Archbishop plus a certain number of pawn[s]) might be to at least drive up the number of resulting unnecessary draws (let alone losses), in a way that may not at a minimum favour the Queen even approximately appropriately as far as its final overall percentage score in playtesting when pitted vs. an Archbishop. In short, I wonder if the results of such playtest games might even still be substantially skewed (setting aside the quality of the play by the engines). At the risk of stating the obvious, viewers can note that even if the Queen wins about the correct ratio of times vs. its losses, an incorrect (say too high) percentage of drawn games skews the overall results percentages if measuring the Archbishop. For example, if in 20 games the Queen wins 8 times, loses 4 times, with 8 draws, for an overall percentage of 60%, it has the same ratio of wins to losses if it wins 10 times and loses 5 times (i.e. with 5 draws), but in the latter case the Queen scores a better overall percentage (of 62.5%). The actual difference due to any playtesting that might be faulty might conceivably be quite greater percentagewise than for these example figures. 25 comments displayedLater ⇩Reverse Order⇧ Earlier⇩ Earliest⇧Permalink to the exact comments currently displayed.