Computer-Dealt Hands

Truly Random or Impishly Fixed?

Computer-generated hands have a bad reputation in some circles—undeservedly so. "These computer hands!" is a common cry, but how different are "computer hands" from people-dealt hands? Also, how does ACBL create these deals?

Let's tackle the second question first. It is a simple matter for a computer to deal a set of 52 cards. To explain how this process works, using an oversimplified analogy, consider how a mailman places letters in a set of post office boxes. Each piece of mail has an address, and the mailman places each piece in the correct box.

Similarly, each card of the deck is randomly assigned a value which determines which "box" (hand) it will be dealt to.

There is a catch, however, and it has to do with the word "randomly." It is important that the computer performs this task in a random fashion. Otherwise there is a risk that the same set of hands will be generated more than once.

Many computers use their internal clocks as a "random" starting value to assign each of the cards an "address." In practice, however, this method isn't sufficiently random enough. The software that ACBL uses to generate deals, therefore, requires an additional step. The staff person whose job it is to create the deals must physically deal out a set of 52 cards, just as you would do at the bridge table. The four hands are entered into the computer. This information, along with the time at which it was entered, create the starting value for the process and ensures that it is completely random. For the more technically inclined, the random number generator uses a linear congruential algorithm that will repeat after 2 to the 47th power (140,737,488,355,328) deals have been generated.

Returning to the question of whether computer-dealt hands are different from people-dealt ones, remember the great emphasis placed on creating a random deal. To create a random deal manually, players must give the deck a thorough shuffle at least seven times to guarantee that the cards are mixed. It is common, however, to see players shuffle the deck only two or three times before dealing. This is not a random deal.

Although it is beyond the scope of this article to demonstrate, it has been been suggested by various mathematical authorities that this inadequate shuffling may lead to "flatter" distributions. In other words, suits may break evenly more often than expected. Players who are accustomed to their trump suits dividing evenly all the time because of inadequate mixing seem genuinely offended when they encounter a 4--1 trump split in a computer-dealt game, even though that division will occur 28% of the time.

"Computer-dealt hands!" they mutter, but in reality they're just getting a dose of a truly random deal.
Another factor which causes some players to believe that computer-dealt hands are different from people-dealt ones is that hand records are usually available after a computer-dealt session. Players then have the opportunity to see all the cards of every deal, and some of these players will use the hand records as "proof" of the "strange distributions" supposedly caused by the computer. If these same players could see hand records from their local club games, they would find that "strange distributions" occur in hand-dealt games as well.

Does anyone at ACBL look at the deals in order to throw out "boring" ones or to include particularly frustrating ones? Never. Repeat: Never. In fact, only two people at ACBL are even permitted to see the hand records. One is the person whose job it is to set up the computer to generate the hand records. The other is the print shop manager who cuts, wraps and labels the hand-record packages. Neither is a bridge player. The hand records are then sealed and shipped to the ACBL warehouse. When needed, they are mailed to the tournament official who orders them. No one at ACBL ever manipulates the deals.

Sometimes players complain that the cards seem to run one direction (usually the direction of their opponents). "North-South had all the cards!" This does occur sometimes, but it happens in people-dealt games as well. George S. Kaufman, the famous New York dramatist and bridge expert, once quipped that clubs should post which way the cards are running as a courtesy to the players. He said this, however, during the 1930s. People have been complaining that their opponents hold all the cards since the days of whist.

Finally, let's not forget the advantages of computer dealing. At NABC+ events, the duplimate machine actually pre-deals several sections of hands based on computer records. Without computers, hand records would not be available at tournaments. It would be too time-consuming to copy all of the information from people-dealt hands.