lifebeyondfife (u/lifebeyondfife)

lifebeyondfife commented on Generating sudokus for fun and no profit tn1ck.com/blog/how-to-gen... · Posted by u/todsacerdoti

xjm · a year ago

I counted one trillion or 9! * 3!^8 * 2 : the 8 because you have can choose 3 independent permutations of columns inside column blocks + 1 permutation of column blocks, plus same for rows. Then only one rotation should be counted, because flips are included in col/row permutations.

I think wreath products relate to the second sentence; see this page, which mentions the same result: https://en.wikipedia.org/wiki/Mathematics_of_Sudoku#The_sudo...

lifebeyondfife · a year ago

You're correct, the horizontal and vertical flips for the square, are already accounted for in the wreath product. And I miscounted the products themselves. Up to 1.2*10^12 symmetries.

lifebeyondfife commented on Generating sudokus for fun and no profit tn1ck.com/blog/how-to-gen... · Posted by u/todsacerdoti

lifebeyondfife · a year ago

The exponential number of symmetries present in sudoku problems, means that once you've found one valid instance, you've actually found up to 9! * 3!^4 * 8 which are exactly the same.

The numbers themselves are all interchangeable, so you have 9! combinations: 362,880.

Columns 1-to-3 are all interchangeable, as are 4-to-6, and 7-to-9. On top of this, these blocks of columns (1-to-3, 4-to-6, 7-to-9) are all interchangeable. Read about wreath products in group theory to know more. Each of the above symmetries are 3!, combined to yield 3! * 3! = 36 combinations. As well as the columns though, the rows have the same property, so those can be combined too: 36 * 36 = 1,296.

Finally, there are the symmetries of a square. Combining all rotations and flips yields a further 8.

In total, sudoku has 3,762,339,840 symmetries. Owing to the starting state of the sudoku puzzle being incomplete, the orbit of the set of points (more group theory) will be smaller than 3 billion, but it provides an efficient method of recreating many more puzzles with the same property. In this case, human complexity.

lifebeyondfife commented on Travle: A daily game – get between countries in as few guesses as possible imois.in/games/travle/... · Posted by u/my12parsecs

charles_f · 2 years ago

Fun game. I'd love to be able to play more than one round a day.

lifebeyondfife · 2 years ago

You can use the waybackmachine. This works for Worldle as well.

http://web.archive.org/web/20231127182010/https://imois.in/g...

lifebeyondfife commented on How to do the thing you've been avoiding jasonfeifer.beehiiv.com/p... · Posted by u/duck

lifebeyondfife · 2 years ago

Wait, But Why? has a fascinating series of posts on this. https://waitbutwhy.com/2013/10/why-procrastinators-procrasti...

I bought the 52x90 poster where each square is a week of your life. I've filled in significant events. It helps me ensure I keep working on making those events coming.

lifebeyondfife commented on Modern SAT solvers: fast, neat and underused (2018) codingnest.com/modern-sat... · Posted by u/weird_user

sirwhinesalot · 2 years ago

There are also Constraint Programming solvers (some SAT based, some not) and (Mixed) Integer Programming solvers (not SAT based).

Each "school" excels at different types of problems. ASP for modelling a knowledge-base and running queries on it, CP for discrete optimization problems or for all-solution search, SMT for formal verification and proofs, MIP for optimization of (mostly) continuous variables.

Modern solvers in these "schools" can do things traditionally meant for other "schools". Z3 can do optimization, clingo can include CP-style constraints with clingcon, some MIP solvers can find all solutions, etc.

All in all, this type of "classical" AI is super interesting and I hope the hype on LLMs doesn't suck up all the funding that would go to research in this area.

lifebeyondfife · 2 years ago

Plug for my Constraint Solver if anyone wants a simple example https://github.com/lifebeyondfife/Decider

lifebeyondfife commented on Show HN: Learn Python with Minecraft github.com/gilesknap/mciw... · Posted by u/gilesknap

lifebeyondfife · 2 years ago

When I worked at Skyscanner, we'd volunteer at events where high school kids would be shown tech stuff. We'd setup Raspberry Pis with Minecraft on them and show them some basics of running Python scripts to alter the world (with the conclusion being programmatically create loads of dynamite blocks and explode them). Then at the end of the session, give every kid their own Raspberry Pi.

It was interesting reaching the occasional child who assumed this kind of thing wasn't for them.

lifebeyondfife commented on What We Learned from Building GovSlack slack.engineering/what-we... · Posted by u/atg_abhishek

jamesfinlayson · 3 years ago

> Maintained and supported by US personnel

Do they just need to be US citizens or is there more to it?

lifebeyondfife · 3 years ago

Only US citizens are permitted to deploy code to the US government production servers, or look at the telemetry from those servers.

(I'm a UK citizen, based in the UK, and I have local colleagues supporting products that are deployed to both commercial .com, and US .gov domains. They deploy to .com themselves, but another team based in the US deploy to .gov)

lifebeyondfife commented on Today is the 1000th day of March, 2020 cov.idmar.ch/... · Posted by u/lifebeyondfife

lifebeyondfife · 3 years ago

The pandemic is ongoing, but despite its lasting impacts e.g. hybrid or remote is the norm, many things are back to normal. One thousand days out, how are things for you?