steve2005 Posted June 27, 2022 Report Share Posted June 27, 2022 My linkWide open in hearts and it cant take all the tricksThis was a just declare so bidding is GibsI think its AJx has to overtake trick 1 and lead back the J Quote Link to comment Share on other sites More sharing options...
johnu Posted June 27, 2022 Report Share Posted June 27, 2022 Good defense by GIB. If you were in a slam, you would have gone down. 1 Quote Link to comment Share on other sites More sharing options...
smerriman Posted June 28, 2022 Report Share Posted June 28, 2022 GIB doesn't make any assumptions that the lead is from a strong suit or that West must have the ten of hearts. Under that assumption, why GIB plays as it does is pretty straightforward. On the first round, it plays the J because that is guaranteed to be at least as good as the Ace double dummy; it assumes it'll know when to overtake on the second round (standard double dummy flaw). On the second round, it plays low because there are too many occasions when overtaking costs a trick at MPs (eg every time declarer has Txx). It comfortably finds the overtake at IMPs, where there's nothing to lose. Quote Link to comment Share on other sites More sharing options...
pigpenz Posted June 30, 2022 Report Share Posted June 30, 2022 so GIB would never lead Q from KQ109...?I gave up on robots, but sometimes get stuck playing withthem when someone leaves a game....they suck! Quote Link to comment Share on other sites More sharing options...
johnu Posted June 30, 2022 Report Share Posted June 30, 2022 so GIB would never lead Q from KQ109...?I gave up on robots, but sometimes get stuck playing withthem when someone leaves a game....they suck!Nah, Q lead is so avant-garde. But maybe the tried and tested 4th best 9. Quote Link to comment Share on other sites More sharing options...
sfi Posted June 30, 2022 Report Share Posted June 30, 2022 GIB doesn't make any assumptions that the lead is from a strong suit or that West must have the ten of hearts. Under that assumption, why GIB plays as it does is pretty straightforward.[...]Now all we need is a justification for the HQ rather than the H9. Does GIB really treat the Q, 10 and 9 as equals in this situation? Quote Link to comment Share on other sites More sharing options...
smerriman Posted June 30, 2022 Report Share Posted June 30, 2022 Now all we need is a justification for the HQ rather than the H9. Does GIB really treat the Q, 10 and 9 as equals in this situation?Well, they are 100% equals after the J has been played.. sure, if West were human, you would play the 9 so that East would have choice but to overtake with the Ace, but that's not something that double dummy analysis could ever tell a robot. Quote Link to comment Share on other sites More sharing options...
sfi Posted June 30, 2022 Report Share Posted June 30, 2022 Well, they are 100% equals after the J has been played.. sure, if West were human, you would play the 9 so that East would have choice but to overtake with the Ace, but that's not something that double dummy analysis could ever tell a robot.So in practice do the robots have a 2/3 chance of defeating the contract or a 0% chance? Quote Link to comment Share on other sites More sharing options...
smerriman Posted June 30, 2022 Report Share Posted June 30, 2022 0% - it'll always continue with the Q; I believe when choosing amongst equals it follows strict rules based on leading conventions etc. Sometimes that rule is to randomise (when following to a restricted choice situation), but in this case is high from equals. Quote Link to comment Share on other sites More sharing options...
sfi Posted June 30, 2022 Report Share Posted June 30, 2022 0% - it'll always continue with the Q; I believe when choosing amongst equals it follows strict rules based on leading conventions etc. Sometimes that rule is to randomise (when following to a restricted choice situation), but in this case is high from equals.I don't believe it randomises in restricted choice situations either - I'm yet to go wrong playing the robot to play the higher (or highest) of equals there. So maybe it just always plays the top of a sequence. Quote Link to comment Share on other sites More sharing options...
smerriman Posted June 30, 2022 Report Share Posted June 30, 2022 Oh that's right, I forgot the forum post where we concluded it always played the higher card. But yeah, distinguishing equals would require recursing into partner's hand which adds a significant amount of computation time. Far too much for GIB at least. Quote Link to comment Share on other sites More sharing options...
pescetom Posted June 30, 2022 Report Share Posted June 30, 2022 Oh that's right, I forgot the forum post where we concluded it always played the higher card. But yeah, distinguishing equals would require recursing into partner's hand which adds a significant amount of computation time. Far too much for GIB at least. Recursion is usually more of a drag on programmer's CPU than that of the computer.Could GIB not in any case maintain a table of equivalence which updates trick to trick with minimal computation time?Just programming laziness I would think. Quote Link to comment Share on other sites More sharing options...
smerriman Posted June 30, 2022 Report Share Posted June 30, 2022 Recursion is usually more of a drag on programmer's CPU than that of the computer.Could GIB not in any case maintain a table of equivalence which updates trick to trick with minimal computation time?Just programming laziness I would think.I'm not sure what you mean. GIB doesn't have a problem computing equivalence. We're talking about *distinguishing* equivalent cards - ie figuring out that playing a low card from equals here will make it easier for East to find the correct defense than playing high from equals. The only way to do that would be recursively - rather than just simulating deals from West's perspective, for every such deal, you have to move into another player's seat and then run a second simulation to see what ideas they might come up with if they had that hand. This recursion results in an exponential increase in the number of simulations run, and the time it takes to perform the calculations would immediately skyrocket. Quote Link to comment Share on other sites More sharing options...
thepossum Posted July 4, 2022 Report Share Posted July 4, 2022 Out of curiosity I put this through another major Bridge program Same auction, led King to East's 4, then switched to diamond, East unblocked hearts during subsequent play, and finally led back the Jack but sadly West had discarded one to many hearts and the contract was made exactly EDIT forced a lead of the Q on trick two, sadly also blocked - I realise it already has been blocked by the play of the 4 and the Queen - my badWill report back if I find anything that defeats the contract. Quote Link to comment Share on other sites More sharing options...
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