Next meeting: random numbers

[Tom Stuart]

Hi all,

Our next meeting will be about The New Turing Omnibus chapter 8, “Random Numbers”, pages 49–55. For those who haven’t yet bought the book and would like to “look inside”, a PDF of the chapter is available in our Slack room:

https://computationclub.slack.com/files/tomstuart/F0BG6J2PL/random-numbers.pdf

The meeting will be 6:30pm next Tuesday (6th) at Geckoboard HQ as usual. If you’re planning to come, please sign up on Lanyrd so that we know roughly how many bags of crisps to buy:

http://lanyrd.com/2015/london-computation-club-october/

See you there!

Cheers,
-Tom

[Tom Stuart]

On 29 Sep 2015, at 16:15, Tom Stuart <t...@codon.com> wrote:
> Our next meeting will be about The New Turing Omnibus chapter 8, “Random Numbers”, pages 49–55. […] https://computationclub.slack.com/files/tomstuart/F0BG6J2PL/random-numbers.pdf

>
> The meeting will be 6:30pm next Tuesday (6th) at Geckoboard HQ as usual.

1. Reminder: we are meeting tonight!

2. Warning: we’re in the habit of starting late and finishing late, but tonight our gracious host (Leo) has to leave at 8:30pm on the dot, so let’s try to start punctually at 6:30pm.

Cheers,
-Tom

[Kevin Butler]

Tom suggested I post to here as we didn't look at it in the meeting:

The linear formula described on page 50, `x_next = (k * x + c) mod m`, is a poor generator for 'random' numbers. Their sequences have repeated loops which often appear quickly, usually with a (relatively) low period. It reminded me of an entropy visualization a friend described to me a while back.

The simulation generates a load of `worms`, each with their own set of values for (k, m, c, x0) and uses their generated sequences to influence their movements.

Due to their short repeating sequences, the worms get stuck in loops which you can see as them moving in patterns. Their movement also (generally) tends towards the edge of the screen as their repeated loops don't have a balanced number of Left, Right, Down and Ups. I think this highlights the lack of a uniform distribution within the loops of the generated sequences.

http://ryman.github.io/new-turing-omnibus/8%20-%20Random%20Numbers/random_walks.html