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Defensive carding: no signalling (attitude / count / suit-preference) is implemented #189

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@ThorvaldAagaard

BEN's defenders do not signal, and do not read partner's signals. When following suit the card comes from the NN, PIMC or double dummy, with no signalling convention applied at all.

The cost shows up as defences that are individually defensible but collectively incoherent. In #136 partner has shown DK but nothing about hearts, so the defence has no way to work out that the club switch is the losing one. In #174 East simply has no way to tell West what he holds.

There are two halves to this and they are not equally hard:

  • Encoding - choose which small card to play to show attitude/count/suit preference. This is a tie-break on cards that are already equivalent, so it can be bolted on without changing the search.
  • Decoding - condition the sampler on partner's signals, so that a signal actually narrows the sample set. This is the hard half and the one that would make the difference.

Encoding without decoding is still worth having: it makes BEN a better partner for a human, even if BEN cannot use the information itself.

Source issues: #174 - #136

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