Contract probabilities of random biddings

In my last post (7NTxx gains over 74% popularity) I wondered why learning results are so bad. But, I understood that the underlying idea was not correct.

My RNN started from random bidding, then is was learned to improve its performance. So, instead of comparison to proper bidding in human sense, we should compare resulting biddings statistics to random bidding statistics.

Looking at the results beloew, I see (no surely, since there is no statistical error analysis), that RNN does better than the random player. Apart from increasing 7NTxx probability, in case of RNN usually the probabilities of high contracts are lower than the probabilities of “normal” ones.

I run 100.000 of random bidding trials and got the following results:

Contract Probability Count
7NTxx 52.72% 52724
7NT 23.38% 23375
7NTx 17.65% 17653
7S 2.68% 2681
7Sx 1.06% 1058
7Sxx 0.94% 941
7H 0.69% 691
7D 0.26% 256
7Hx 0.19% 190
7C 0.09% 94
7Hxx 0.09% 88
6NT 0.06% 60
7Dx 0.05% 49
6S 0.04% 35
7Cx 0.02% 22
6H 0.02% 21
7Dxx 0.02% 17
6C 0.01% 8
6D 0.01% 5
6NTx 0.01% 5
6Sx 0.00% 3
6Cx 0.00% 3
5H 0.00% 2
5NT 0.00% 2
4S 0.00% 2
5S 0.00% 2
7Cxx 0.00% 2
4H 0.00% 2
5C 0.00% 2
6NTxx 0.00% 1
4C 0.00% 1
4NT 0.00% 1
6Dx 0.00% 1
1C 0.00% 1
6Hx 0.00% 1
4Sx 0.00% 1

We can calculate the probability of final contracts in some simple cases, directly.  E. g.

  • the probability of PASS (4 passes) is: (1/36)^4 (the same for each bidding like:  some_bid, pass, pass, pass)
  • the probability of 7NT contract after 7NT bid has happened is 0.25
  • the probability of 7NTx (doubled) contract after 7NT bid is 0.1875
  • and so the probability of 7NTxx (redoubled) contract after 7NT bid is 1-0.25-0.1875 = 0.5625

So the probability of 7NTxx contract (without assumption that 7NT was bid) is not greater than 0.5625.

After nightly run, on 1.320.000 trails the results are:

Contract Probability Count
7NTxx 52.67% 695222
7NT 23.44% 309436
7NTx 17.60% 232270
7S 2.72% 35908
7Sx 1.05% 13823
7Sxx 0.92% 12209
7H 0.69% 9127
7D 0.25% 3254
7Hx 0.19% 2443
7C 0.11% 1492
7Hxx 0.09% 1216
6NT 0.06% 750
7Dx 0.05% 673
6S 0.03% 455
7Cx 0.02% 280
6H 0.02% 250
7Dxx 0.02% 222
6D 0.01% 185
6NTx 0.01% 97
6C 0.01% 96
5NT 0.01% 88
7Cxx 0.01% 73
6Sx 0.00% 61
5S 0.00% 58
5H 0.00% 42
5D 0.00% 38
6Hx 0.00% 34
5C 0.00% 22
6NTxx 0.00% 21
6Dx 0.00% 16
4NT 0.00% 15
4S 0.00% 13
6Sxx 0.00% 12
4D 0.00% 11
5NTx 0.00% 9
6Cx 0.00% 9
5Sx 0.00% 8
3NT 0.00% 6
4H 0.00% 5
5Hx 0.00% 5
3D 0.00% 5
4C 0.00% 4
5Cx 0.00% 4
6Hxx 0.00% 4
2H 0.00% 4
3C 0.00% 4
4NTx 0.00% 3
3H 0.00% 2
2NT 0.00% 2
1C 0.00% 2
6Dxx 0.00% 2
2S 0.00% 2
2C 0.00% 2
1D 0.00% 1
5Dx 0.00% 1
4Sx 0.00% 1
1NT 0.00% 1
3S 0.00% 1
1H 0.00% 1
4Dx 0.00% 1