[suokko]

suprgrover, on Dec 7 2009, 05:20 AM, said:

pran, on Dec 6 2009, 06:42 PM, said:

I know about BigDeal and the fallacy in showing how you need a 96 bits random generator. (Yes, there is a fallacy there!)

Could you explain what you mean here? There are between 2^95 and 2^96 possible bridge deals, so what is wrong with using 96 bits?

Because you don't need to use if your generator has long enough period to generate enough random bits for the set of deals. I don't know what sizes generator is good enough but at least pran is claiming that 32bit PRNG is enough.

[suprgrover]

suokko, on Dec 6 2009, 11:02 PM, said:

Because you don't need to use if your generator has long enough period to generate enough random bits for the set of deals. I don't know what sizes generator is good enough but at least pran is claiming that 32bit PRNG is enough.

But the period of a generator tells us how long until the sequence repeats. The idea behind having 96 bits is to ensure that every deal could be generated; with fewer bits I do not see how you can include all possible deals in the set of deals that the program could produce.

[suokko]

suprgrover, on Dec 7 2009, 07:56 AM, said:

But the period of a generator tells us how long until the sequence repeats. The idea behind having 96 bits is to ensure that every deal could be generated; with fewer bits I do not see how you can include all possible deals in the set of deals that the program could produce.

I can take 3 (32bit) random numbers and append them to each other to produce 96 bits of information.

Better of course would be only using the most random part of that 32 bit and append more numbers to each other to produce the full 96 bits.

[Echognome]

I was the person who noticed this problem.

I simply don't understand all the discussion about the possibility or impossibility of the boards being the same. They were the same. I believe the problem was when the deals were made and I'm pretty sure it was human error, rather than computer error. The boards were pre-dealt, so there was no issue of a player making the error.

I called when dummy came down, because I remembered my hand from the previous board, which was now dummy's, to the pip. I had less of a recollection of the hand I held from the previous board as it was an opponent's, but it seemed like it was the exact hand. I called the director and went away from the table to tell him to check. He did and confirmed there was an error.

Those are the facts. The question is what is the ruling? Should the cancelled boards be scored as is? Should they be given average plus (no players at fault)? Or should they be scored as average or average minus (as no one else noticed)?

Those seem to be the salient questions to me.

[pran]

Echognome, on Dec 7 2009, 10:10 AM, said:

I was the person who noticed this problem.

I simply don't understand all the discussion about the possibility or impossibility of the boards being the same. They were the same. I believe the problem was when the deals were made and I'm pretty sure it was human error, rather than computer error. The boards were pre-dealt, so there was no issue of a player making the error.

I called when dummy came down, because I remembered my hand from the previous board, which was now dummy's, to the pip. I had less of a recollection of the hand I held from the previous board as it was an opponent's, but it seemed like it was the exact hand. I called the director and went away from the table to tell him to check. He did and confirmed there was an error.

Those are the facts. The question is what is the ruling? Should the cancelled boards be scored as is? Should they be given average plus (no players at fault)? Or should they be scored as average or average minus (as no one else noticed)?

Those seem to be the salient questions to me.

This completes the story with important information.

You informed the Director about your suspicion without giving away any indication on the problem to the other players at the table, that was very good and in fact the correct procedure.

Now we are in Law 6D2 territory, and at your table the correct ruling would be to replace the board with a correct one if possible or award A+ to both sides. (As I understand you there was no "correct" board.)

The rest of this thread has gone into a discussion on computerized card dealing.

regards Sven

[pran]

suprgrover, on Dec 7 2009, 04:20 AM, said:

pran, on Dec 6 2009, 06:42 PM, said:

I know about BigDeal and the fallacy in showing how you need a 96 bits random generator. (Yes, there is a fallacy there!)

Could you explain what you mean here? There are between 2^95 and 2^96 possible bridge deals, so what is wrong with using 96 bits?

It is nothing wrong (provided it is shown that each possible result will occur with the correct probability), but it is not neccessary.

Traditional shuffling routines use 51 (separate) random numbers to determine the transformation of one shuffled card deck into the next. So even after for instance 2^32 random numbers have been used and a new full cycle is started upon in the generator there will not be any apparent repetition of already created deals.

There is even more to this question, but I shall try not to "overflow" the thread.

regards Sven

[helene_t]

suokko, on Dec 7 2009, 07:31 AM, said:

I can take 3 (32bit) random numbers and append them to each other to produce 96 bits of information.

But if the random number generator only uses 32 bits to represent its state, then you can never get more than 32 bits of entropy out of it. A sequence of 3x32 bits will contain only the first 32 bits of entropy - the remaining 64 bits are determined by the first 32 and therefore contain 0 (conditional) entropy. So if there are really 2^95 hands, you can only generate a small subset of them.

Practically speaking, it would probably work to create three different initial seeds (for example by reading the user's keystroke tempo 3 times) and then initiate three different random number generators and run them in parallel, generating each hand from the concatenation of the current states of the three generators. This procedure will repeat itself after 2^32 boards rather than 2^96, but the user is likely to have rebooted the system before you come that far . (I would then use 4x32 rather than 3x32 to make sure that it wouldn't be possible to guess the next deal if you recognize one deal).

[axman]

pran, on Dec 7 2009, 05:12 AM, said:

Echognome, on Dec 7 2009, 10:10 AM, said:

I was the person who noticed this problem.

I simply don't understand all the discussion about the possibility or impossibility of the boards being the same.  They were the same.  I believe the problem was when the deals were made and I'm pretty sure it was human error, rather than computer error.  The boards were pre-dealt, so there was no issue of a player making the error.

I called when dummy came down, because I remembered my hand from the previous board, which was now dummy's, to the pip.  I had less of a recollection of the hand I held from the previous board as it was an opponent's, but it seemed like it was the exact hand.  I called the director and went away from the table to tell him to check.  He did and confirmed there was an error.

Those are the facts.  The question is what is the ruling?  Should the cancelled boards be scored as is?  Should they be given average plus (no players at fault)? Or should they be scored as average or average minus (as no one else noticed)?

Those seem to be the salient questions to me.

This completes the story with important information.

You informed the Director about your suspicion without giving away any indication on the problem to the other players at the table, that was very good and in fact the correct procedure.

Now we are in Law 6D2 territory, and at your table the correct ruling would be to replace the board with a correct one if possible or award A+ to both sides. (As I understand you there was no "correct" board.)

The rest of this thread has gone into a discussion on computerized card dealing.

regards Sven

We were informed subsequently that the hand records matched the cards for boards 9 & 10. This suggests that the computer generated the hands legitimately as played.

And merely because such an occurence is improbable, this player by not holding his tongue has destroyed probably the one opportunity in this solar system to experience the anomaly [legitimately].

[aguahombre]

LOL. Echo, I think you should give up trying to get an answer. Nobody wants to accept that there was a human error and fouled board(s). The presence (if true) of a hand record showing both hands as they were only means the human error occurred at a different point.

Even if it was a computer malfunction, to allow continued play of hands where the other players' hands are known or knowable cannot be right. Continued shooting of the messenger cannot be helpful, either.

[gordontd]

aguahombre, on Dec 7 2009, 06:16 PM, said:

I think you should give up trying to get an answer.

I'll give what I think is a practical answer, using L6D1 and L16C as my legal basis, but fully accepting that it's not water-tight.

Boards 9 & 10 are materially different, because of the rotation, dealer & vulnerability. Those who have already played them have valid comparisons that can be made with each other, and so I would score them as they were played.

Now we have a player who has recognised the hands in Board 10 and who is therefore in receipt of extraneous information and who will need to be awarded an artificial score (A+/A+) under L16C. Since we know that there may be others who will be in that position, we should now redeal Board 10 to avoid having to issue further artificial scores, and then at the end of the game we can score it as a fouled board, with those who played it in one form compared with each other, and those after the redeal scored separately. Board 9 can continue to be played and scored as normal (assuming they are playing 2-board rounds and the two boards are in the same board-set).

This post has been edited by gordontd: 2009-December-07, 11:53

[blackshoe]

That looks familiar, Gordon. In fact, it looks very much like what I said early in this thread.

[nige1]

aguahombre, on Dec 7 2009, 12:16 PM, said:

LOL.  Echo, I think you should give up trying to get an answer.  Nobody wants to accept that there was a human error and fouled board(s). The presence (if true) of a hand record showing both hands as they were only means the human error occurred at a different point. Even if it was a computer malfunction, to allow continued play of hands where the other players' hands are known or knowable cannot be right.  Continued shooting of the messenger cannot be helpful, either.

I agree that Echognome behaved impeccably, confiding his suspicions to the director alone. I still believe that there remains a problem with pseudo-random hand generation. If you examine a set of boards and something seems peculiar to you, then where do you draw the line? Examples ...

• The North hands have a lot of tens.
  
• The West hands have a lot of voids.
  
• Two hands are all one suit.
  
• Several hands have four aces.
  
• There are lots of nine card suits.
  
• North-South consistently hold more HCP than East-West.
  
• Two consecutive West hands are the same.
  
• Two deals are the same.

Had you predicted any of these, you would have received good odds against their occurrence. After the event, however they are no less likely than any other specific set of boards. (Except in human hind-sight). When computer-deals were introduced, directors sometimes redealt boards that seemed anomalous to them. Unfortunately, however, if you retrospectively cull deals, you no longer have random boards.

[gordontd]

blackshoe, on Dec 7 2009, 10:20 PM, said:

That looks familiar, Gordon. In fact, it looks very much like what I said early in this thread.

Yes, you're quite right. It seems I'm in good company.

[mjj29]

nige1, on Dec 7 2009, 04:23 PM, said:

Examples ...

• The West hands have a lot of voids.
  
• Two hands are all one suit.
  
• Several hands have four aces.
  
• There are lots of nine card suits.

Sounds like the boards I generate for the christmas party

[pran]

nige1, on Dec 7 2009, 10:23 PM, said:

aguahombre, on Dec 7 2009, 12:16 PM, said:

LOL.  Echo, I think you should give up trying to get an answer.  Nobody wants to accept that there was a human error and fouled board(s). The presence (if true) of a hand record showing both hands as they were only means the human error occurred at a different point. Even if it was a computer malfunction, to allow continued play of hands where the other players' hands are known or knowable cannot be right.  Continued shooting of the messenger cannot be helpful, either.

I agree that Echognome behaved impeccably, confiding his suspicions to the director alone. I still believe that there remains a problem with pseudo-random hand generation. If you examine a set of boards and something seems peculiar to you, then where do you draw the line? Examples ...

• The North hands have a lot of tens.
  
• The West hands have a lot of voids.
  
• Two hands are all one suit.
  
• Several hands have four aces.
  
• There are lots of nine card suits.
  
• North-South consistently hold more HCP than East-West.
  
• Two consecutive West hands are the same.
  
• Two deals are the same.

Had you predicted any of these, you would have received good odds against their occurrence. After the event, however they are no less likely than any other specific set of boards. (Except in human hind-sight). When computer-deals were introduced, directors sometimes redealt boards that seemed anomalous to them. Unfortunately, however, if you retrospectively cull deals, you no longer have random hands.

This is why regular and comprehensive statistic testing of the outcome from such programs is important, and also why it is important to examine particularly what happened when such unacceptable results were produced.

It is possible to throw six sixes in a row with a dice (it can be expected once in 7776 trials), but if that happens daily in a gambling house any serious house would take that dice out of service and examine it very carefully before admitting it into service again.

Similarly a computer dealing program that occationally exhibits strange results should be examined (together with its logs) to see if there is some flaw waiting to be revealed.

WHAT! There are no logs available that can be examined afterwards to find out exactly what happened inside the program?

Oh dear.

[thomaso]

nige1, on Dec 6 2009, 03:29 PM, said:

I believe that Thomas Andrews' dealing program will generate all possible hands (eventually). Richard Pavlicek's dealer is similarly excellent and fast. They both have all kinds of fascinating stuff!

My "Deal" program does not, in fact, generate all possible deals. My Impossible Bridge Book does, but "Deal" does not use that code. Instead, it is engineered to generate lots of samples quickly.

[helene_t]

nige1, on Dec 7 2009, 10:23 PM, said:

If you examine a set of boards and something seems peculiar to you, then where do you draw the line? Examples ...[LIST]
[*] The North hands have a lot of tens.
[*] The West hands have a lot of voids.

The best advice is always to assume that the cards were dealt randomly, even in the presence of extreme statistical abnormalities. The thing is, people find patters where there are none.

Even in this case, where two boards were identical down to the last pip, I think there is a case for treating it as a coincidence and just let the boards be played:
- Most players didn't notice.
- A software bug could be considered a "random" event (as long as we aren't talking about well-known software bugs causing predictable abnormalities).
- We don't want to create precedence for directors with a bad intuition for probabilities (and most everyone has very bad intuition for probabilities) to reshuffle boards whenever he thinks something looks strange. For every genuine bug in a dealing program there will be literally thousands of false positives.

[blackshoe]

I take your point about setting a precedent, Helene, but as Gordon said, here we have a player who has extraneous information about board ten. Are we to simply to give an artificial adjusted score on this board, and hope that anyone else who recognizes the problem calls the TD so he can get the same, or do we let them play on, with that extraneous knowledge?

[helene_t]

blackshoe, on Dec 8 2009, 03:53 PM, said:

I take your point about setting a precedent, Helene, but as Gordon said, here we have a player who has extraneous information about board ten. Are we to simply to give an artificial adjusted score on this board, and hope that anyone else who recognizes the problem calls the TD so he can get the same, or do we let them play on, with that extraneous knowledge?

As it turned out, the complete deal (including the two hands he couldn't see) were identical down to the last pip.

I think as a TD, I would just assume the much more likely case namely that the two deals were just very similar (maybe down to two or three pips) and that it was just a coincidence so that the two hands he couldn't see might be completely different.

And then tell the player to play on and say he could use information from the previous deal if he wanted, if he really thought the other two hands were also identical, which I would not know. (For all we know the software bug might have produced two deals that were identical w.r.t. two hands but not w.r.t. the other two).

I would then be proved wrong afterwards, and would be torn between canceling the board, or assigning a splitscore so that this player's opponents were not damaged, or whatever.

But I think in most such cases I would be right.

[blackshoe]

If I'm not mistaken, the table TD determined that the two boards were indeed identical down to the last pip before he made his table ruling. Given that knowledge at that time, would you still make the same ruling?

If you did so rule (let's say you didn't know they were identical) and it later turned out your assumption was wrong, is that not TD error, requiring you to adjust the score treating both sides as non-offending?