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List:       kde-games-devel
Subject:    Re: Fixes for KPat Forty & Eight patience game
From:       Albert Astals Cid <aacid () kde ! org>
Date:       2020-07-16 20:38:53
Message-ID: 23805772.n42G4Vui09 () xps
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El divendres, 10 de juliol de 2020, a les 7:38:40 CEST, Ian Wadham va escriure:
> Hi guys,
> 
> Good news. In brief, I have found two or three causes of the 10 bugs listed in
> https://bugs.kde.org/buglist.cgi?quicksearch=kpat%20forty%20eight.
> 
> However, I am going to need help from an expert with a knowledge of the KPat code \
> to work out the most appropriate patches. 
> I will also need help to get patches committed, when they are ready, because I do \
> not have access to or knowledge of the newer KDE Community repositories and \
> procedures. 
> The bug list above relates to false positives and negatives from the 48 solver and \
> touches on problems with the Autodrop feature. The false reports from the solver \
> were easy enough to fix in patsolve/fortyeightsolver.cpp. However, when I tested my \
> fixes, I found that the false positive had been fixed but the false negative was \
> still there. 
> The false positive is due to the 48 solver generating an invalid move and using it \
> to reach a win, then saying that the game is winnable when it is not. The human \
> player cannot win because he/she is not able to make that move, except by using \
> Demo to bypass it ;-). Actually the 48 solver generates invalid moves quite often \
> (as shown by Hint), but they are not always used or needed in a winning solution. 
> Forty & Eight is a 2-pack game. False negatives can occur when there are two cards \
> of the same suit and rank that can "go out" onto a foundation pile. The 48 solver \
> always chooses the card on the left and ignores the other one. Sometimes playing \
> the card on the right leads to a win, and the left hand card is a loser or not a \
> good choice. 
> For example, stack 0 (on the left) may have a 2 of hearts on top and other suits \
> beneath, whereas stack 4 may have the 2-3-4 of hearts in sequence and nothing else \
> beneath, and then an ace of hearts comes out of the talon (or heap). The solver \
> will consider only the 2 on the left to "go out" onto the ace, but the other 2 \
> would almost always be the better option because three cards can go out, rather \
> than one, and they will leave an empty stack 4 as well. Empty stacks are an \
> advantage in later play. 
> When I had fixed the 48 solver to deliver both cards that can go out, Autodrop \
> kicked in (specifically bool DealerScene::drop() in file dealer.cpp) and undid my \
> good work. It uses DealerScene::getHints() to get a list of playable moves and \
> selects out those that go out to foundation (or target) piles. Trouble is that if \
> there are two cards of the same suit and rank in the list, Autodrop always plays \
> the first (leftmost) one. It then returns, letting the animation of the move \
> proceed, but when it is called back the second card is no longer playable (nor \
> hinted) because the first card has taken its spot. In this kind of situation \
> neither card should be autodropped. The human player should be left with a choice \
> as to which card to play, unless it does not matter (e.g. if each card is the only \
> one in its pile and either can go out first). 
> I have developed a patch to fix DealerScene::drop(). It takes effect only if the \
> current game is Forty & Eight, because I am worried about adversely affecting other \
> KPat games. I have looked at other multiple-pack games, but Mod3 and Gipsy do not \
> seem to use Autodrop. I am not so sure about Spider, but perhaps it also is \
> affected by Autodrop grabbing cards too soon. 
> Unfortunately my patch is rather kludgey. It is also a pity that it cannot get at \
> some information known to the 48 solver and passed back to the main KPat solver, \
> patsolve/patsolve.cpp, i.e. which possible moves are automatable. If there are two \
> cards of the same suit and rank that can go out, the 48 solver flags neither one as \
> automatable. 
> I really need help from a KPat expert to work out what is the best thing to do \
> here.

Unfortunately I don't think we have many KPat experts around anymore, Shlomi and \
Fabian are the two that did changes to somewhat core parts lately.

My suggestion would be for you to put the patch as a Merge Request in invent.kde.org \
and that way we all can have a look at it and maybe try to understand it together.

Cheers,
  Albert



> 
> Cheers,
> Ian Wadham.
> 


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