I would love to see someone pick up a $100,000 "Magic: The Gathering" vintage deck and giving it seven riffle shuffles saying, "The maths doesn't lie!" :P
The Math of Card Shuffling (2018)
61–65 of 65 posts
Re: The Math of Card Shuffling (2018)
#62Earlier quoted context omitted.
It you want to see more amazing, Ricky Jay could do this while keeping up a stream of amusing patter and making his hand motions seem almost casual. E.g. https://www.youtube.com/watch?v=eonlrksCsw8
Richard Turner does it with patter, casual motions, and while being blind. https://en.wikipedia.org/wiki/Richard_Turner_(magician)
He had some interesting appearances on Penn and Teller's show 'Fool Us': https://www.youtube.com/watch?v=TwFIJyWKs1k
Re: The Math of Card Shuffling (2018)
#63There's a sort of magic trick involving doing perfect riffle shuffles where the whole deck retains it's order. If my memory is correct if you perform 8 perfect riffle shuffles (split deck 50/50, riffle one for one card correctly) then the order resets itself after 8 shuffles. It's usually only performed as a demonstration of skill by experienced card magicians than as a standalone trick.
This really makes my head hurt, haha. I've always heard the 7 shuffles to be randomized. Great. But if I shuffle one more time it's back to where I started? How does that makes sense?! Of course, this is dependent on perfect shuffles, which I'm sure I never achieve. Maybe the 'seven shuffles to randomize' calculation takes into account the 'human' nature of shuffling during a game? It is almost a sure thing the deck…
Two different meanings of perfect are being used. For eight "perfect" riffles to return to the starting order, you've got to split the deck perfectly in half, and then drop one card from one half, then one from the other, and so on alternating. For perfect randomness, choose at random which half to drop a card from each time.
Re: The Math of Card Shuffling (2018)
#64There's a sort of magic trick involving doing perfect riffle shuffles where the whole deck retains it's order. If my memory is correct if you perform 8 perfect riffle shuffles (split deck 50/50, riffle one for one card correctly) then the order resets itself after 8 shuffles. It's usually only performed as a demonstration of skill by experienced card magicians than as a standalone trick.
Yes it's 8 perfect riffles. What the article doesn't seem to stress is that there are two different riffles—an in shuffle (top card moves to second) and an out shuffle (top card stays on top). It's only 8 with an out shuffle I think, but 52 with an in shuffle. So presumably their figure of 7 is referring to the in shuffle (as being 1 shuffle away from the original order doesn't sound too shuffled to me). The in shuff…
Your statement about in shuffles for general n is false. Consider that an in shuffle on n cards is identical to an out shuffle on the middle n of n+2 cards.
Also, the statement in the article is for a random riffle, not a perfect one. Any deck which has only been perfectly riffled is entirely determined.
Re: The Math of Card Shuffling (2018)
#65An interesting bit if history. Electronic card shuffles were invented by a former truck driver. Casinos rented the devices from his company I don't think any were sold (their value was approximately $20,000 each). I haven't worked at a casino for four years but at that time I beleive the market opened up. It sounds like a patent expired or maybe the fisr card shuffle company was sold.
You can buy card shufflers on Amazon for under twenty dollars. I've only used one once and geez was it loud - hopefully they do not all have that issue. https://www.amazon.com/card-shuffler-automatic-card-shuffler...
The casino type shuffler have cameras to read the cards and remember the order of the cards after shuffling them. It also has a pseudorandom number generator it uses as a guide to shuffling randomly. You need to set the card type before loading too. Casinos order their own cards so you need to make sure the shuffler can read them.
At casinos there's so many proprietary devices for example a small plastic block like a prism the size of a quarter. It sits on the table in the area where the dealer sets his cards. Blackjack dealers use it to view their cards when face down only they can see the image. Just that little stupid plastic block is patented and costs something like $10 per device per day for every casino that leases them.