[JanM]

ggwhiz, on 2011-September-03, 10:30, said:

Kudos to whomever arranged to have such calls known as "BS" bids.

I believe that would be Edgar Kaplan

[lamford]

gombo121, on 2011-August-31, 23:38, said:

Concerning practical realization of the RNG, there is a very simple method - shuffle your hand before you look at it and then interpret red cards as zeros and black cards as ones - you get 13 bits of randomness, which should be enough for any practical purpose!
(OK, it won't work in online bridge, but then you probably can use RNG of your PC directly).

A much better method of randomising an opening bid, which you can disclose easily to opponents, and will have considerable advantages in the play, is the following, which we employ against strong clubbers, where ANY defence is permitted:
Bid Description Frequency
1NT Any deuce 0.696
1S Any trey 0.212
1H Any four 0.064
1D Any five 0.020
The lower card takes priority for deciding which bid to make. So 1D means you have a five, but no card of lower rank.

There are many advantages when defending because you know, if your partner overcalls 1S, he has no deuce and at least one three, so information may be available to you but not to declarer. You need to be careful playing the card you are known to have sometimes! This method is, bizarrely, allowed over a two-card club suit at level 2 in the Newbridge Novice Pairs under Orange Book 11M2. Disclosure under OB10A6 can certainly be full and frank. I think it is Brown Sticker for an opening bid, however.

[lamford]

wyman, on 2011-August-31, 14:30, said:

An idea that is often floated around the poker community is to use the position of the seconds hand of your watch as an RNG.

A breach of 40C3(a) in bridge, however; a watch could not be used, for example, to decide which to play from QJ doubleton.

[barmar]

hrothgar, on 2011-September-02, 16:27, said:

On average, the "even" cards are weaker than the odd cards.

You're right, because the lowest card is even, and the highest card is odd. So there's an assymetry in my "increase by 1 = decrease by 1", because you can't increase beyond an ace or decrease below 2.

The person who suggested the odd/even method said to ignore aces because they cause an imbalance between even and odd. But including them would solve this problem, since the highest and lowest cards would be even.

[aguahombre]

barmar, on 2011-September-04, 16:20, said:

The person who suggested the odd/even method said to ignore aces because they cause an imbalance between even and odd. But including them would solve this problem, since the highest and lowest cards would be even.

Are you sure that one or 13 is even?

[hrothgar]

barmar, on 2011-September-04, 16:20, said:

You're right, because the lowest card is even, and the highest card is odd. So there's an assymetry in my "increase by 1 = decrease by 1", because you can't increase beyond an ace or decrease below 2.

The person who suggested the odd/even method said to ignore aces because they cause an imbalance between even and odd. But including them would solve this problem, since the highest and lowest cards would be even.

What's more significant in terms of the difference in trick taking?

The difference between a King and a Queen or the difference between a deuce and a trey?

[barmar]

hrothgar, on 2011-September-04, 17:26, said:

What's more significant in terms of the difference in trick taking?

The difference between a King and a Queen or the difference between a deuce and a trey?

Even better point. Maybe ignore all honor cards, and compute the parity of the spot cards.

[hrothgar]

barmar, on 2011-September-05, 21:45, said:

Even better point. Maybe ignore all honor cards, and compute the parity of the spot cards.

Or, alternatively, use a system that works like the one I showed earlier...

[phil_20686]

You could get a very simply, and fairly accurate way of getting simple fractions by doing modulo arithmetic. Give every card a number between 1 and 13, total them, and now if you divide by, say 3, and take the remainder, it is very close to a 1/3 chance.

Interestingly, this is a simple appplication of the central limit theorem, it works because there are so many cycles of modulo three, up to a typical hand total, that the probability distribution is essentially Gaussian (and hence uncorrelated). You could use this to give you accurate fractions of anything up to about 6 I think. This ought to be enough randomisation.

[hrothgar]

phil_20686, on 2011-September-06, 07:59, said:

You could get a very simply, and fairly accurate way of getting simple fractions by doing modulo arithmetic. Give every card a number between 1 and 13, total them, and now if you divide by, say 3, and take the remainder, it is very close to a 1/3 chance.

Interestingly, this is a simple appplication of the central limit theorem, it works because there are so many cycles of modulo three, up to a typical hand total, that the probability distribution is essentially Gaussian (and hence uncorrelated). You could use this to give you accurate fractions of anything up to about 6 I think. This ought to be enough randomisation.

For anyone who needs a simple explanation:

Let's assume that there is some action that you want to take 1/4 of the time.

• Add up the value of all your cards using a 1:13 scale
  
• Divide by 4
  
• If the remainder is 1, take the action
  
• If the remainder is not one, do something else

If you wanted to take an action 20% of the time (1/5th of the time) simply divide by 5

There are a couple problems with this technique:

1. Here, once again, the strength of your hand is correlated with the RNG

2. When we sum the cards, we get something that looks close to a bell curve. When we take the mod of the sum, numbers close to the peak are going to occur more often. (Hence Phil's comments about choosing small values like 1/2 - 1/6)

Personally, I still like my transitions scheme which generates a uniform distribution.
If we can pull eight bits off the transitions - which seems reasonable if we include both rank and suits - and marry this to the Phil's modulus suggestion we get the best of both worlds...

Cards = 1:13
Cards = Cards'
Cards = repmat(Cards,4,1)

%% shuffle

simlength = 1000000

MC_Result = zeros(simlength, 1);

for i = 1:simlength

index = randperm(52);
Cards = Cards(index);
Card_Sum = sum(Cards(1:13));
Running_Card_Sum(i) = Card_Sum;
MC_Result(i) = mod(Card_Sum,4);

end

tabulate(Running_Card_Sum)

Value    Count   Percent
      1        0      0.00%
      2        0      0.00%
      3        0      0.00%
      4        0      0.00%
      5        0      0.00%
      6        0      0.00%
      7        0      0.00%
      8        0      0.00%
      9        0      0.00%
     10        0      0.00%
     11        0      0.00%
     12        0      0.00%
     13        0      0.00%
     14        0      0.00%
     15        0      0.00%
     16        0      0.00%
     17        0      0.00%
     18        0      0.00%
     19        0      0.00%
     20        0      0.00%
     21        0      0.00%
     22        0      0.00%
     23        0      0.00%
     24        0      0.00%
     25        0      0.00%
     26        0      0.00%
     27        0      0.00%
     28        0      0.00%
     29        0      0.00%
     30        0      0.00%
     31        0      0.00%
     32        0      0.00%
     33        0      0.00%
     34        0      0.00%
     35        0      0.00%
     36        0      0.00%
     37        0      0.00%
     38        0      0.00%
     39        1      0.00%
     40        0      0.00%
     41        1      0.00%
     42        2      0.00%
     43        3      0.00%
     44        5      0.00%
     45        9      0.00%
     46       12      0.00%
     47       13      0.00%
     48       32      0.00%
     49       41      0.00%
     50       54      0.01%
     51       80      0.01%
     52      105      0.01%
     53      149      0.01%
     54      178      0.02%
     55      274      0.03%
     56      367      0.04%
     57      453      0.05%
     58      635      0.06%
     59      773      0.08%
     60     1084      0.11%
     61     1318      0.13%
     62     1643      0.16%
     63     1957      0.20%
     64     2419      0.24%
     65     2962      0.30%
     66     3610      0.36%
     67     4431      0.44%
     68     5213      0.52%
     69     5923      0.59%
     70     6981      0.70%
     71     8252      0.83%
     72     9502      0.95%
     73    10853      1.09%
     74    12155      1.22%
     75    13781      1.38%
     76    15277      1.53%
     77    17014      1.70%
     78    18921      1.89%
     79    20259      2.03%
     80    21877      2.19%
     81    23693      2.37%
     82    25247      2.52%
     83    26853      2.69%
     84    28288      2.83%
     85    29350      2.94%
     86    30834      3.08%
     87    31693      3.17%
     88    32632      3.26%
     89    33040      3.30%
     90    33619      3.36%
     91    33486      3.35%
     92    33185      3.32%
     93    33083      3.31%
     94    32476      3.25%
     95    31501      3.15%
     96    30625      3.06%
     97    29393      2.94%
     98    28009      2.80%
     99    26812      2.68%
    100    25237      2.52%
    101    23647      2.36%
    102    22210      2.22%
    103    20280      2.03%
    104    18555      1.86%
    105    16760      1.68%
    106    15274      1.53%
    107    13500      1.35%
    108    12209      1.22%
    109    10933      1.09%
    110     9391      0.94%
    111     8353      0.84%
    112     7178      0.72%
    113     5965      0.60%
    114     5160      0.52%
    115     4391      0.44%
    116     3704      0.37%
    117     3176      0.32%
    118     2453      0.25%
    119     1965      0.20%
    120     1673      0.17%
    121     1303      0.13%
    122      999      0.10%
    123      828      0.08%
    124      624      0.06%
    125      463      0.05%
    126      340      0.03%
    127      279      0.03%
    128      222      0.02%
    129      153      0.02%
    130      108      0.01%
    131       73      0.01%
    132       48      0.00%
    133       38      0.00%
    134       25      0.00%
    135       15      0.00%
    136        9      0.00%
    137        5      0.00%
    138        4      0.00%
    139        5      0.00%
    140        2      0.00%
    141        1      0.00%
    142        2      0.00%
    143        1      0.00%
    144        0      0.00%
    145        1      0.00%

[semeai]

We're discussing two types of randomization methods here:

1) Those due to shuffling your hand. For example, gombo121's first mention of this with red = 0, black = 1 (which suffered from being correlated with hand type), my suggestion using an absolute order of the cards to read off a permutation of the 13 cards, and hrothgar's suggestion of using transitions to get bits. The latter two have no correlation with hand type/strength. (I happen to prefer mine, as it contains much more info as well as being better suited to getting probabilities with denominators not a power of two, but the bits from transitions should be okay too. Really it's just a special case that records a manageable amount of data.)

2) Deterministic ones based on the cards you hold, such as gwnn's suggestion of adding up the spots and taking the remainder modulo something and lamford's suggestion of using whether you hold a 2, whether you hold a 3, etc.

Is there a regulatory issue with either one? It seems unlikely, but (1) could be ruled as using an outside aid (though it seems just to use the cards) or as being impossible to disclose (though I think it should be fine just to tell what the method is). It also seems unlikely, but (2) could be disallowed for being encrypted (though partner doesn't have the key).

If there's no regulatory issue, I don't know why you wouldn't use one of the uncorrelated methods from (1). Also, methods that use shuffling but have a correlation with hand type/strength seem strictly worse than either uncorrelated ones from (1) or (minimally) correlated ones from (2).

[Vampyr]

semeai, on 2011-September-06, 11:47, said:

If there's no regulatory issue, I don't know why you wouldn't use one of the uncorrelated methods from (1). Also, methods that use shuffling but have a correlation with hand type/strength seem strictly worse than either uncorrelated ones from (1) or (minimally) correlated ones from (2).

Clearly the order in which the cards are picked up could create a more-or-less "random" situation, whereas methods based on one's actual holding are clearly not, as they are, after all, based on your hand. It seems to me that this kind of treatment is legal, as long as you disclose to your opponents your method of randomising/choosing.

[semeai]

Vampyr, on 2011-September-06, 12:38, said:

It seems to me that the order in which the cards are picked up could create a more-or-less "random" situation, whereas methods based on one's actual holding are clearly not. It also seems to me that this kind of treatment is legal, as long as you disclose to your opponents your method of randomising.

You don't have to do it based on how you pick up your cards, which could be influenced by the previous table's shuffling or lack thereof. You can shuffle them before you look at them. Of course if you're doing this every board (so as not to give away when your hand requires a random number to help decide your bid) it might get tiresome.

[lamford]

semeai, on 2011-September-06, 11:47, said:

(2) could be disallowed for being encrypted (though partner doesn't have the key).

Even if the opening bid is decided to be encrypted, and I do not think that is the meaning of encrypted, ANY defence to a two-card club opening is permitted, even in a novice event, so it can be used as an overcall. A 1NT overcall of a 2-card club suit, stating "I'm present at the table",, is allowed at level 2.

So you might disallow it in a 192-board brown sticker event as an opening bid, but it is still legal in the EBU over a short club in the Palmer Bayer (a supposed No-Fear event).

[Free]

snip

[FrancesHinden]

lamford, on 2011-September-04, 04:47, said:

A much better method of randomising an opening bid, which you can disclose easily to opponents, and will have considerable advantages in the play, is the following, which we employ against strong clubbers, where ANY defence is permitted:Bid Description Frequency1NT Any deuce 0.6961S Any trey 0.2121H Any four 0.0641D Any five 0.020The lower card takes priority for deciding which bid to make. So 1D means you have a five, but no card of lower rank. There are many advantages when defending because you know, if your partner overcalls 1S, he has no deuce and at least one three, so information may be available to you but not to declarer. You need to be careful playing the card you are known to have sometimes! This method is, bizarrely, allowed over a two-card club suit at level 2 in the Newbridge Novice Pairs under Orange Book 11M2. Disclosure under OB10A6 can certainly be full and frank. I think it is Brown Sticker for an opening bid, however.

lamford, on 2011-September-07, 17:29, said:

Even if the opening bid is decided to be encrypted, and I do not think that is the meaning of encrypted, ANY defence to a two-card club opening is permitted, even in a novice event, so it can be used as an overcall. A 1NT overcall of a 2-card club suit, stating "I'm present at the table",, is allowed at level 2.So you might disallow it in a 192-board brown sticker event as an opening bid, but it is still legal in the EBU over a short club in the Palmer Bayer (a supposed No-Fear event).

Is there some reason you needed to post this twice?
I think it is more surprising that you are allowed to open a suit that may only have 2 cards in it at level 2. If you aren't happy with highly conventional defences to your methods, play natural opening bids. No 'novice' or 'no fear' player should ever have to worry about coming up against random defences, because they can play a simple system instead.

[gordontd]

lamford, on 2011-September-07, 17:29, said:

Even if the opening bid is decided to be encrypted, and I do not think that is the meaning of encrypted, ANY defence to a two-card club opening is permitted, even in a novice event, so it can be used as an overcall. A 1NT overcall of a 2-card club suit, stating "I'm present at the table",, is allowed at level 2.

So you might disallow it in a 192-board brown sticker event as an opening bid, but it is still legal in the EBU over a short club in the Palmer Bayer (a supposed No-Fear event).

The Palmer Bayer is a simple-system event that doesn't allow short club openings. I hope you and Bob Brinig didn't break the rules when you won it, Paul!

[helene_t]

zip

[Zelandakh]

Is bridge not one of the few games where coming up with an almost completely accurate RNG for 20% actions is possible? When you first pick up your hand, shuffled naturally, observe the first card between 2 and 6 and compute its remainder (or subtract 1 of preferred). If no card between 2 and 6 is held then use 7 to jack instead (remainder or subtract 6). You can use the remainder from the last board as the check digit - if they match then take the 20% action. Alternatively you could take a decahedral die with you and roll it between rounds out of sight of anyone else. As for the concept, seems perfectly legal to me - many systems have more than 1 bid to describe a given hand type.

[nige1]

Sorry, my post may flout IBLF guide-lines. Anticipating another deletion, I've reposted to "General bridge discussion"