Some of you may think this is a silly question and I looked at the entire Café for an appropriate place to post and this is the best I could do. It's about cards, so here goes....

I read recently that to truly get a random order from 52 cards that a new deck must be shuffled 7 times in a riffle type shuffle. It's apparently a mathmatical proof and the sixth shuffle still produces some "patches" of runs and suits, but the seventh shuffle seems to do the trick, as it were.

So. Do any of you have thoughts on the results of using an automatic shuffler? Are the mechanics of these things equivalent to the human hands doing a riffle shuffle? What about the introduction of shuffling multiple decks, as might be done in Blackjack?

I'm appealing here to the experience of cardicians who are intimately familiar with the randomn distribution results of shuffling. I'm not a card guy myself and I'm just looking to see where this discussion goes. Loooking forward to your thoughts!

For some light reading on the randomness of riffle shuffling see:


MATHEMATICAL DEVELOPMENTS FROM THE AN......LING
Persi Diaconis

For some threads on automatic shufflers, see here...


Brian

I remember having an automatic shuffle machine when I was younger and it was like doing faros, not that I knew that name at the time. It took cards from two piles and alternated them. If it did it perfectly then eventually it could return to the same order I suppose. Maybe they have changed or there are different ones that are more random.

Kingman

Brian, thanks for the links......I recently ordered Magical Mathematics by Diaconis....waiting to receive it.

Kingman, there are all kinds of deck shufflers out there today, but as with anything else, you get what you pay for. I've seen 'em from three dollars to several hundred dollars....and I'm not sure any one of them will do a job any better than the next. The human hand is more dexterous than a couple of motorized rubber rollers, but I'm interested to know of personal experiences with them.

Thanks guys!

The reason for the automatic shuffling machine is that it removes the human hands from the process. People tend to trust machines to be honest. However, as we magicians know, you could also program an automatic shuffler to leave a portion of the deck undisturbed, or even switch a randomized deck for one completely set up in your favorite series. Oh, what a wicked web we weave when first we practice to deceive!

Motorized rubber rollers are found only on the crudest of machines. Fro example, one form of automated shuffler - that made the inventors rich, by the way - was built to "truly" randomize 6 decks at a time; here's how it works:

1) six decks (312 cards total) are loaded into a stacked hopper;
2) a computer chip generates a random number falling between 1 and 312;
3) a mechanical picker grabs the card that lies in the randomly chosen position and makes it the bottom card of the new multi-deck stack;
4) a random number falling between 1 and 311 is generated;
5) that card is placed in the second-from-bottom position of the new stack;
6 etc., until all 312 positions of the new multi-deck stack are filled.

TW