How to shuffle cards like a pro: Mathematician shows why the 'riffle' technique is more effective than the flashy 'overhand'
comments
It takes practice to perfect shuffling a deck of cards in a fast and flashy way.
But a mathematician has pointed out that card aerobatics do not guarantee a random and well shuffled pack.
Peri Diaconis compared different shuffling techniques and it seems that the 'riffle shuffle', which involves cutting a deck in half and shuffling the halves into each other, is the most time effective - if done well.
Scroll down for video
Peri Diaconis compared different shuffling techniques and said the 'riffle' shuffle (pictured), which involves cutting a deck in half and shuffling the halves into each other, is the most effective and random if done well
In a Numberphile YouTube video, the Stanford University mathematician said that if a dealer uses a riffle shuffle, they only need to repeat the process seven times to get a good mix.
If they are well adept at the card manoeuvre, this could take less than 30 seconds.
But if they use a flashier overhand shuffle, which involves quickly inserting random chunks of cards from one hand into the majority of the deck of cards held in the other, they will need to do it 10,000 times to achieve similar results.
This could still be fast in the hands of experts, but still slower than the riffle method.
'There's a third way of mixing cards - used in poker tournaments and Monte Carlo - I call that smooshing,' Dr Diaconis said.
If a dealer uses an overhand shuffle (pictured), which involves quickly inserting random chunks of cards from one hand into the majority of the deck of cards held in the other, they will need to do it 10,000 times to achieve similar results to the riffle shuffle
The method, which is also known as wash, corgi and chemmy, involves randomly laying the cards face down on a table and messing them up with the hands over and over again. It is used in professional poker tournaments.
The method looks random and is – if it is done for a long enough period time.
'If you smoosh for a minute it passes every test we've ever thrown at it.
'If you smoosh for 30 seconds, it seems ok, but less than that it starts failing tests and someone could make money against you or guess cards,' Dr Diaconis said.
This means that while the method is thorough, if done for a minute, it too is slower than the riffle method.
A technique called smooshing (pictured) also known as wash, corgi and chemmy, involves randomly laying the cards face down on a table and messing them up with the hands over and over again. It needs to be done for around one minute for the cards to be truly random and difficult to guess
Dr Diaconis explained in the video how mathematicians check that shuffling is random.
He said that there are a staggering 80,658,175,170,943,878,571,660,636,856,403,766,975,289,505,440,883,277,824,000,000,000,000 configurations in a perfectly random deck.
'It's more than the number of particles in the universe,' he said.
One way of defining randomness is that all card configurations should be equally likely.
He said that if a deck of cards is perfectly shuffled, you may expect to guess between four and five cards correctly as they are pulled out one by one from a pack.
But if they are not shuffled enough – for example, if a pack is riffle shuffled four times instead of seven - people might guess nine or ten cards correctly.
In the simplest form of shuffling, where a person takes one card from the top of a deck and inserts it at random, it would take '200 or so pokes' before the deck is random.
Put the internet to work for you.
0 comments:
Post a Comment