The Nineteenth Byte

1:09 AM

Q: Antisymmetry of a Matrix

A matrix is antisymmetric, or skew-symmetric, if its transpose equals its negative. The transpose of a matrix can be obtained by reflecting its elements across the main diagonal. Examples of transpositions can be seen here: \$\begin{pmatrix}11&12&13\\21&22&23\end{pmatrix}\rightarrow\begin{pmatrix}11

1:35 AM

@Lyxal /list/listen/

~~/steam/grill/~~

1 hour later…

Q: Fastest prime printer up to 500,000,000

2:50 AM

Write a program to print the first 26,355,867 prime numbers, from 2 to 499,999,993 inclusively. Or in other words, print all the prime numbers smaller the 500,000,000. The fastest code wins! The program must not use any preprocessed input. The results will be tested on my machine

primes fastest-code

3 hours later…

5:55 AM

Asking for last feedback on this (changed the task to not require outputting initial terms) cc @mypronounismonicareinstate @user202729 @xnor

6:25 AM

@Bubbler I suspect that there might be some way to cheat if initial terms are not required.

@AviFS The "3 days" rule is only specified in a post in the sandbox FAQ. If most people agree that it's important enough to be in the main sandbox "question" post then it can be moved there (someone may want to make a meta post about that)

Although (I suspect that) some users active on main already-never visit the sandbox (or review the sandbox posts not as carefully), so longer might not be better.

@user202729 How? It is my intention to give some room for finding the recurrence without the terms.

@bubbler ... thinking about it again, it's not that easy. But it's still possible to output the product of every candidate polynomial.

For example... if I somehow can prove that the length is <= 2m , all coefficients are integers, and abs(coefficients) is <= 2^m then the program can output the product of every such polynomial.

... that product isn't particularly pretty.

6:45 AM

@user202729 Then I could limit the order k to 2^m or something

Or polynomial in m.

I don't think polynomial will work, because empirically the minimal order for small m looks like O(2^(m/2)).

But the matrix size is polynomial in m.

And the minimal polynomial degree has the size <= matrix size?

To me it's 2^m rows/columns, and I don't see any trivial way to shrink it other than vertical mirror images

... right.

Then exponential in m.

2^m is better, I guess.

A: Sandbox for Proposed Challenges

7:10 AM

Good, now it's limited to k<=2^m.

1 hour later…

New Sandboxed Posts

8:32 AM

Minimal cost path in wall-breaking maze code-golf grid maze puzzle-solver Inspired by this Puzzling challenge. Challenge Given a 2D rectangular grid where each cell is either an empty space or a wall, find the path (or one of the paths) that satisfies the following: The path breaks (or passes th...

Newly Featured Questions

Q: Optimal Games of Tic Tac Torus

This challenge is about the game Tic Tac Toe, but it's played on a torus. How to play To create the necessary game board, you start out with a regular Tic Tac Toe game board. First fold it into a cylinder by joining the left and the right edge. Then fold it into torus by joining the top and th...

code-golf game tic-tac-toe

1 hour later…

9:51 AM

Help! I have a natural conflict against fastest-code challenges!

Luis Mendo

10:15 AM

This meta question by @xnor addresses allowed outputs for [tag:decision problems]. But in that question the goal isn't to make a policy, but to help with a decision I often have to make when writing challenges

I think we do need a policy, so that when people don't specify we can assume some default output allowed in [tag:decision problems]. Should we post a new meta question and answers so people can vote? Or do we use @xnor's question and its answers to decide the policy?

10:47 AM

Implicit rule: If you downvote Dennis, you are evil.

Why doesn't my badge system work?

Next badge
36/40
Vox Populi
Despite I already used 40 votes today.

@HighlyRadioactive Refresh the page the next day.

(Did you only upvote question today?)

Wdym?

@HighlyRadioactive You need to upvote questions only, in order to get the maximum 40 votes.

Why is there this restriction

No I upvoted almost questions only

But with the exceptions of your few answers LOL

cwl

:55137224

Why don't everyone upvote my ~~turth~~ truth-machine?

11:04 AM

@HighlyRadioactive Is there some in-area joke I'm missing here?

2 hours later…

12:43 PM

@Third-party'Chef' What you forgot your own language?

12:56 PM

@HighlyRadioactive I created so many languages on esolangs.org such that I forgot almost all of them...

You should've make a list.

I like to surf on the ~~internet~~ language lists

That's how I found 1+

Including normal language list, stack-based language list, joke language list, and many more

1:31 PM

@LuisMendo Third option: Post answers to the existing Default I/O post and let people vote.

Luis Mendo

1:54 PM

@Bubbler Yas, sctually that's what I meant with my second option: use its answers, including new ones

Luis Mendo

2:35 PM

But that would require @xnor's transforming the original question into a policy question

1 hour later…

Q: Fastest prime printer up to 500,000,000 [to be reopened]

3:53 PM

Q: Draw an ASCII-art rainbow

Draw an ASCII-art rainbow! Input An integer between 0 and 1000, inclusive. Examples Input 0: /\ || Input 1: _ / \ | | Input 2: __ / \ | | Input 3: ___ / \ | | This is code-golf. Shortest code wins.

code-golf ascii-art

New Meta Posts

I would like to edit my question here, so it can be reopened. Here is the new body of the question, please tell me what do you think? Write a program to print the first 26,355,867 prime numbers, from 2 to 499,999,993 inclusively. Or in other words, print all the prime numbers smaller the 500,000...

discussion