The Nineteenth Byte - 2019-01-27

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Pavel

00:19

How do you override the [] operator in python, i.e. change what foo[bar] returns?

lirtosiast

@ASCII-only You don't need the **.5

Erik the Outgolfer

@Pavel if bar is a single operand, then you override the __getitem__ attribute

Pavel

thanks

ASCII-only

00:38

@lirtosiast oh wait true

@EriktheOutgolfer wait. only single?????

Erik the Outgolfer

well... if you have a : in everything changes... :P

ASCII-only

fixed

@EriktheOutgolfer firstly... that's still a single parameter...

secondly... all that happens is it gets passed a slice object instead of a normal one...

Erik the Outgolfer

actually, a[b:c:d] is just a[slice(b,c,d)]

ASCII-only

exactly

Erik the Outgolfer

but... overriding __getitem__ if you just want the b is easier ;)

if you want the b and c but not the d, there's a handy __getslice__ method you can override as well, but... __getitem__ also covers the case where you're given a slice

rant: why did you make a[b:c] separate from __getitem__...

Downgoat

01:35

@ASCII-only should ??.getValue() + 1 compile to { $0.getValue() } + 1 or { $0.getValue() + 1 }

2 hours later…

PhiNotPi

03:37

chat mega challenge: nasa.gov/sites/default/files/atoms/files/…

Anonymous

04:21

@ASCII-only Golly doesn't yet support neighborhoods of radius 2

Downgoat

04:44

@PhiNotPi actually on this topic I think PPCG's @AshwinGupta developed code for a cubesat for his school

PhiNotPi

04:56

I really want to have a personal satellite someday. Launch prices are low enough that it wouldn't break any laws of finance... just difficult.

Downgoat

@PhiNotPi I mean it's a around 100K launch and then I'd expect 40K development costs not to mention cost of labs and other development resources. Though I think NASA does cover launch costs if you're selected

PhiNotPi

05:24

Echo - Landing Test #2

check this guy out though... his channel is a quest to make a mini falcon heavy

Anonymous

I finally got around to making some test cases for an old sandboxed challenge of mine

Anonymous

I would appreciate any feedback

Neil

11:31

@ASCII-only Oblong seems to be broken: ＵＯ¹χXO¶OX

Neil

12:13

@ASCII-only RotateTransform seems to be very broken: ≔⮌⪪θ¶θ⊟θ⟲Ｔ⁵Ｍ→⮌θ

Erik the Outgolfer

@Mego what if I told you... that LaTeX doesn't want to render a sum properly...

Erik the Outgolfer

12:41

@Mego alright, a question: since "summing over all..." looks a bit weird when converting the post to LaTeX, maybe I can rephrase it as (u,w)\in E under the \sum?

dzaima

13:39

@ASCII-only well you've literally got a built-in for it :|

but yeah Charcoal has a higher chance of beating Canvas on simple/line-y challenges

1 hour later…

New Main Posts

14:46

0

Q: Help Me Play Quantum Go-Fish!

Introduction We all know the game of Go-Fish. Everyone has numbered cards, and on their turn they get to ask another play if they have any of (some number). If they do, they hand those to you. When you have four of a kind, you lay them down and continue. But today you won't be implementing Go...

code-golf game card-games

ASCII-only

15:07

@Downgoat hmm I'd say expand till braces or parens probably?

@Mego wait wat are you serious

@Mego then... How do they do larger than life

dzaima

@ASCII-only i assume mego meant that golly doesn't support custom rules for radius 2, not them in general

1 hour later…

New Main Posts

16:23

1

Q: The Path Of The Wildebeest

Golf a program or function which gives the \$n^{\text{th}}\$ location of the wildebeest who starts at square \$1\$ on an infinite chessboard which is numbered in an anti-clockwise square spiral, where the wildebeest always visits the lowest numbered square she can reach that she has not yet visit...

code-golf sequence integer chess

PhiNotPi

17:18

@Doorknob hello

Doorknob

17:29

@PhiNotPi o/

PhiNotPi

how's life?

Doorknob

pretty good, how are you?

PhiNotPi

I've been busy with med school interviews... not much else though.

Doorknob

ah, that sounds fun

good luck!

PhiNotPi

Thanks

I've been reading up about satellites, space computers, etc. recently.

Unfortunately I can't afford any of the cool space parts right now.

Doorknob

17:44

I'd imagine they'd be rather expensive

feersum

18:02

Why med school?

PhiNotPi

@feersum Basically I feel that it is a uniquely rewarding/"meaningful" career and I believe I have a lot I could contribute to the field.

feersum

Well I dunno, accounts I've seen usually suggest that contact with the actual medical system quickly crushes the notions of helping people, being meaningful or whatever.

Are you thinking more a practicing doctor or an academic, or what?

PhiNotPi

I'm focused mainly on the academic side of things... I'm actually applying mainly for MD/PhD dual-degree programs.

It's true that there are lots of issues with physician burnout, especially in the US system.

feersum

18:19

I guess if you are researching there is perhaps less concern about that. I suppose you still have to the usual stuff like a residency though?

PhiNotPi

Yeah, residency will be intense.

Jonathan Allan

18:32

@EriktheOutgolfer hmm, odd - if I run my code with a knight or camel the generator raises a StopIteration at the correct point, while I ran it for a wildebeest and got to 150 million, posted and called next(g) and got a StopIteration. I made a mistake somewhere but am not yet sure where... I've done it again and had the same at ~22m - unsure what's going on.

Erik the Outgolfer

are you sure it's wrong?

Jonathan Allan

...code: tinyurl.com/y78whrjj

I dunno, maybe it always gives the StopIteration once I kill a loop and then try to call __next__?

Erik the Outgolfer

first of all, you're using list.append and you're calling a function extend... :P

Jonathan Allan

and?

Erik the Outgolfer

nah, just a little remark, haven't looked at it thoroughly yet

Jonathan Allan

18:37

I think I just cant kill (ctrl-c) a loop and expect the iterator to still work. I just killed one and called next and it gave me 1.

:p

Erik the Outgolfer

wait, are you killing stuff? ;P

Jonathan Allan

yeah when counter got to 150m

btw - code at TIO is slightly wrong - I didn't edit in to use deltas. This is fixed for that: tinyurl.com/y9omfeve

Erik the Outgolfer

hm, so, I'm pretty sure the extend function is correct

not checking that

also, yeah, just noticed lol

@JonathanAllan can I see how you're testing the iterPath function?

(not link, obviously won't work :P)

Jonathan Allan

I was doing a while 1: and printing a counter every 100k, and calling _=next(it) where it=iterPath(). It raised at end of Knight & Camel, so I think that there probably are > 150m terms for wildebeest :)

(it=iterPath() before entering while that is)

Erik the Outgolfer

(heheheh)

so, looks like your extend function adds four sides :P

Jonathan Allan

18:51

it does.

Erik the Outgolfer

as to why it might raise a spontaneous StopIteration, well, that's really weird

Jonathan Allan

adds the next spiral layer

Erik the Outgolfer

and that yield 1 line makes me wish Python had do...while...

Jonathan Allan

can do a for too, but that doesn't leave the iterator around to continue. I guess I could collect all the results and just look at resulting length & end values to check...

Erik the Outgolfer

here's the thing... we don't know if it will ever end...

Jonathan Allan

18:54

no, but if it does end within 150m we should :p

Erik the Outgolfer

also... another creepy thing I noticed... not isn't a function!!

Jonathan Allan

no, the parens are for eval-order

kicking off:

res = []
for n, v in enumerate(iterPath(), 1):
    if n%100000==0: print(n/1000000)
    res.append(v)

Erik the Outgolfer

@JonathanAllan but... the parens don't do anything

comparison operators have higher priority than not

anyway, I'll reformulate that piece of code a bit and continue trawling

Jonathan Allan

LOL oh yeah - they are now redundant - used to be more in there :)

Erik the Outgolfer

not all(0 <= row + deltaRow < len(spiralArray) and 0 <= column + deltaColumn < len(spiralArray) for deltaRow, deltaColumn in deltas)

^ simpler version

yeah I like simplifying things

DemCodeLines

19:01

Is there a generally accepted way of authenticating API endpoint access?

Erik the Outgolfer

@JonathanAllan umm... ok, what does this part do?

            row += 1
            column += 1

Jonathan Allan

simpler = better :)

Erik the Outgolfer

and, talking about simplification, you can then remove the and and make a nice choo choo of comparison ops over there :P

Jonathan Allan

if we extend the spiral by a layer we are now one further down-right (as it extends in every direction)

Erik the Outgolfer

ah, right

so, that might be a bit optimizable, let's see further down...

Jonathan Allan

19:10

@EriktheOutgolfer except that does not simplify anything as one more comparison op is required - just becomes harder to read for no gain, right??

Erik the Outgolfer

0 <= row + deltaRow < len(spiralArray) > column + deltaColumn >= 0

you can also swap the end terms with the middle term and change the direction of the ops, but you want the larger one (if possible) to be in the middle

Jonathan Allan

oh, ok - no extra :) still harder to read

Erik the Outgolfer

yeah, that's why I didn't include that above

you avoid calculating the length twice though

Jonathan Allan

that's mostly golf though - how much does it actually improve? (length is not calculated, it's a property of the underlying list object)

Erik the Outgolfer

yeah, it just fits in all in a line where I avoid

    this
stuff happening to
    me

anyway, I'm a bit more down now already

yep, just finished reading, everything looks fine

@JonathanAllan so, are you still receiving spontaneous StopIterations? hm...

Jonathan Allan

19:21

not using ctrl-c in the repr with a while loop - just collecting terms. Will see when I reach 150m

(at 100m now)

...meanwhile Arnauld is golfing his solution

Erik the Outgolfer

oh huh lol

Jonathan Allan

but that solution uses recursion so cant be used for 150m :p

Erik the Outgolfer

so... I just spotted he's been golfing that for about an hour

Deadcode

Why is this sitting at 0 votes :\ codegolf.stackexchange.com/questions/121731/…

Erik the Outgolfer

can't be sure, although asking for upvotes is discouraged

Deadcode

19:31

I'm not asking for upvotes, I'm asking why it's sitting at zero

I'm guessing people might see "factorial" and "modified X mins ago Deadcode" and assume I'm just editing the regex post.

Erik the Outgolfer

that nobody can know for sure :P

also, the front page here doesn't have that much demand tbh

trichoplax

Drawing attention to your own posts isn't forbidden, but can look like a request for upvotes even if only implicit. In answer to your question, it's hard to tell - it's possible very few people have seen it yet as 10 hours isn't a long time. I wish there was a view counter on answers instead of just questions, but I can't see how that could be reliably implemented...

Erik the Outgolfer

very hard to implement, what if I'm just scrolling by?

@JonathanAllan so, reached 150m yet? :P

Deadcode

I was only curious as to why this is happening. I wouldn't be upset at all, were it not for the fact that a new C++ answer to the same question, of much more bytes and much slower execution speed, got 1 upvote about 10 hours ago.

trichoplax

@EriktheOutgolfer yes exactly

Erik the Outgolfer

19:37

@Deadcode no need to be upset, votes aren't objective, might be bad luck, might be some other surprising reason... move on! ;)

trichoplax

@Deadcode I wouldn't take +/-1 vote too seriously - there's a lot of noise in the system so until there's a significant difference it's fairly meaningless which answer is higher

Erik the Outgolfer

^ regarding that, well, even Tim Post has done that by mistake :P

trichoplax

Accidentally voted?

Erik the Outgolfer

lol don't you know the infamous meme?

trichoplax

I live in a bubble and don't see many memes...

Erik the Outgolfer

19:43

Tim lost his keys and blah blah blah and a golf ball went into an innocent user's house and made him click a downvote button while the user didn't have time to undownvote as he had to, er, scavenge for and remove that stray golf ball off his house!

oh wait I might have altered it a bit...

Deadcode

Yikes! Right, because you can't undo a downvote after a certain amount of time unless the post has subsequently been edited?

trichoplax

That does sound vaguely familiar - I may have heard it and then mostly forgotten it...

Erik the Outgolfer

just linked to it :P

Deadcode

Thanks.

trichoplax

@EriktheOutgolfer That confirms it - I already upvoted so I must have seen it at some point

Erik the Outgolfer

19:47

well, the actual story is a bit more terrifying

feersum

You must not have read it, as if you had you would already understand that voting on an answer is no proof of having read it.

3

Deadcode

LOL.

Touché.

Erik the Outgolfer

@feersum but isn't a proof of the opposite too...

trichoplax

@Deadcode some of the delay in upvotes may be due to declaring zero to be a natural number :P

Deadcode

@trichoplax Hm, really? Is there actually any disagreement about that?

trichoplax

19:51

In mathematics, the natural numbers are those used for counting (as in "there are six coins on the table") and ordering (as in "this is the third largest city in the country"). In common mathematical terminology, words colloquially used for counting are "cardinal numbers" and words connected to ordering represent "ordinal numbers". Some definitions, including the standard ISO 80000-2, begin the natural numbers with 0, corresponding to the non-negative integers 0, 1, 2, 3, …, whereas others start with 1, corresponding to the positive integers 1, 2, 3, …. Texts that exclude zero from the natural...

For this reason I recommend challenge authors always specify explicitly whether zero is a possible input

Deadcode

Well yeah, to be complete it has to say that :) But in practice, does anybody use the 1,2,3,... definition?

trichoplax

It's what I was taught in the UK, but I just generally try to avoid the term and say "positive integers" or "non-negative integers" to be explicit

Quintec

@Deadcode The 1,2,3 definition is the more commonly accepted... so yes?

Deadcode

I would expect it might be taught that way in elementary school (primary school), but surely not at later stages of education?

trichoplax

The challenge isn't very clear because of that, and also it says "Your program must not produce errors for any input" despite also saying "You can assume that the input number will always be in the range of numbers supported by your language"

@Deadcode Bachelor level

Deadcode

19:57

I do vaguely remember being surprised the very first time I read a definition of natural numbers including zero, because the very first definition I'd learned excluded zero.

But since then, I've only ever seen natural numbers being treated as including zero

Erik the Outgolfer

@trichoplax I have it as an example here lol

the first example, no less

Deadcode

@trichoplax Wow, that is surprising. In what context, may I ask?

Quintec

@Deadcode Same question to you, in what context?

Deadcode

@Quintec Number theory; formal systems of expressing true statements of number theory

The Peano axioms

1. 0 is a natural number.

Quintec

@Deadcode Actually, Peano originally wrote 1.

Deadcode

20:01

@Quintec Seriously? :O

But then you have no additive identity!

trichoplax

@Deadcode I remember it from a lecture course on conjecture and proof, rather than a course specifically on number theory

@Deadcode That's OK - you have no additive inverses either

Deadcode

@trichoplax What do you mean by that? You have subtraction. And in a formal system with no subtraction symbol, you can just say things like ∀a:∃b:∃c:a=b+c

But that statement is no longer true if 0 is not a natural number. It won't be true for a=1

trichoplax

Ah I see. Good point

Jonathan Allan

@EriktheOutgolfer was busy cooking, computer ran out of memory but had reached 175m

Quintec

20:17

@JonathanAllan The exact opposite of "was busy coding, cookies burned" xD

Jonathan Allan

:p

trichoplax

Could you extend the search by removing squares that are no longer reachable? Keeping a set of only those which might be visited in future?

It sounds like it'll still run out of memory eventually but hopefully will go for longer

Jonathan Allan

@trichoplax almost certainly, it's pretty naive code (see the tiny url to TIO of code ^)

tinyurl.com/y9omfeve

Erik the Outgolfer

@JonathanAllan ouch...

time to rent an EC2 :P

@trichoplax @JonathanAllan how do you define "no longer reachable" though?

Jonathan Allan

visited + islands I guess (although I don't think there are any islands yet, but if there are it would prove the path is not a permutation of the natural numbers!)

mind you the data structure to store the pruned space might end up being quite memory hungry itself

Erik the Outgolfer

20:32

islands like patches of unvisited squares with a thick enough border so that the Wildebeest can't jump in?

Jonathan Allan

yeah

but look at what I said about when 1 million is reached - all the unvisited squares are pretty near the outside

(although not amazingly near...)

Erik the Outgolfer

well... yeah, although tri's suggestion is actually removing the ones that are "no longer reachable"

having a set of visited squares is kind of necessary...

Jonathan Allan

visited squares are also "unreachable" right?

Erik the Outgolfer

not always

a visited square might be the one Wildebeest was on at the previous step

Jonathan Allan

she doen't revisit squares, so once visited they become "unreachable"

she could get there by move rules, but not by "wildebeest path rules"

Erik the Outgolfer

20:37

yeah, but if you don't keep a reference to them she will actually start visiting them... that would be a guaranteed 1 → 10 → 1 → 10 → ...

as I read it, tri is suggesting that you remove ones that are "no longer reachable" from the set of visited squares to save memory

Jonathan Allan

if we remove squares that are unreachable by that metric then we remove no squares and save no memory :/

but if we remove ones she may not revisit, and if the code only allows her to move to existing or outwardly extended space then we remove loads.

Erik the Outgolfer

well... maybe we can remove squares that have been "islanded", but, while that might free some memory, it will definitely not be nice regarding the time...

Jonathan Allan

agreed. What we really want is a formula :p

Erik the Outgolfer

inventive mode on... turns off after 0.1s

Jonathan Allan

LOL

at least my curry is delicious

Erik the Outgolfer

20:46

bon appetit! :P

Jonathan Allan

21:07

reached 150099999 squares. 150 millionth square visited was 150276947. While the final 10 I found were [148644237, 148693005, 148644231, 148692999, 148741775, 148790559, 148644221, 148692989, 148644216, 148692984].

...also verified that all 150099999 visited square are unique.

Erik the Outgolfer

then it ran out of memory?

150099999 doesn't sound very promising... :P

Jonathan Allan

no I had a break point

lirtosiast

Interesting coincidence then

Erik the Outgolfer

@JonathanAllan ah the every 100k breakpoint? :P

probably not a coincidence, his tester stops every 100k steps

Jonathan Allan

every 100k (mod == 0) was printing and then if > 150m I broke

Erik the Outgolfer

21:12

well... the numbers are only ~1.3m off so far as it seems... :P

Jonathan Allan

huh?

oh

she was visiting smaller numbers at the end, yes

lirtosiast

wait how would all 150099999 squares be unique then

Jonathan Allan

because she has also visited higher numbers

the results are in res and len(res) is 150099999 and len(set(res)) is also 150099999

max(res) is 151015140

smallest as yet unvisited is 148145652

feersum

21:48

If (1, 0) is not visited after 1 million terms isn't that awfully suspicious (that not all cells are visited)?

Jonathan Allan

@feersum (1,0) there means layer 1 has zero unvisited squares (i.e. square 1 has been visited)

feersum

I see

Jonathan Allan

(2,0),...,(494,0) means all the squares of the inner 494 layers have been visited

...and when we complete 150.1m we find all those unvisited at 1m were, indeed, visited at some point (probably fairly quickly)

I feel like there's probably a really simple geometrical argument that proves she never gets trapped (and maybe one that proves she leaves no square unvisited)

feersum

OTOH, maybe there's no clean proof and not getting trapped is only caused by high mobility.

Jonathan Allan

yep, and maybe she eventually does

Deadcode

21:59

Okay, made a C++ implementation of this... it keeps going and going. For example Step 381681664: Position 382822186

Step 776994816: 775033811

Step 1429209088: 1426568391

What's the highest any of you have got to so far?

Jonathan Allan

@Deadcode Nice, can you first confirm step 150m is 150276947?

Deadcode

I'll have to restart it... I'm only printing every 1048576th

I'll run a second instance

Jonathan Allan

being C++ it's probably fast! Are you pruning the space as you go?

Deadcode

Step 150000000: 150276947

Jonathan Allan

nice

Deadcode

22:04

Nope, not even pruning

Just using 8 GB

Jonathan Allan

yeah Python lists are heavy :(

and indeed each int is an object

feersum

Bit or byte vectors?

Jonathan Allan

so has memory overhead

Deadcode

One bit per position

Here's the coordinate-to-position function I came up with. Did you come up with a simpler one?

int64 coordToPos(int64 x, int64 y)
{
int64 m = max(abs(x), abs(y));
int64 a = 2*m-1;
return a*a + (-y == m && x <= -y ? 3*m + 2*a + 1 + x
: x == m ? m + y - 1
: 4*m - 1 - x - y);
}

ah, indentation was removed

feersum

I wouldn't think you need to use the position numbers at all for the actual simulation.

Jonathan Allan

22:06

click "fixed font" button

Deadcode

Of course you do. You need the smallest

You need to go to the smallest position-index at each step. So how can you do it without this?

Jonathan Allan

^ yep that :)

feersum

Instead, you could compare by ring and then break ties by using knowledge of which quadrants have the smaller numbers.

Quintec

@JonathanAllan Woah, i've somehow never seen that button before until now

Deadcode

Maybe I should restart this with a 21 GB array... looks like it's going to be going for a while

Quintec

22:08

def f(x):
	print("test")

how have I never figured this out before

feersum

I don't know the button but I do know Ctrl+K

Jonathan Allan

Ctrl+K
also works in rooms?

Deadcode

Step 8630829056: 8599687906

Restarted it with a 21 GB array

Jonathan Allan

8.6b :o

doesn't prove she will go forever but she goes far!

Quintec

def f(x):
	print("wait I knew Ctrl+K before but for some reason thought it did something different")

Deadcode

22:20

Alrighty, reached the point I was at before.

Holy shit

Step 12899581952: 12878593430
Trapped!

the trapped position could be up to 1048575 after that

Jonathan Allan

:o

Deadcode

in that version I didn't print it

I'll make it save the array to disk this time

Jonathan Allan

this is awesome!

Deadcode

and print the trapped final position

YES IT IS

Quintec

22:35

inb4 "oops, I printed the wrong position." waits another 5 minutes repeat

Deadcode

Heck, I'm happy that my implementation of handling being trapped worked

Deadcode

22:54

Trapped at step 12899744968 at position 12851850257!

Jonathan Allan

@Deadcode Nice - I'll add this info to the post and the proposed OEIS entry! (if the entry at OEIS gets created it may be worth sharing your code... would you place it in a TIO?)

Deadcode

I'll put it on github

Jonathan Allan

cool, thanks

Deadcode

kingbird.myphotos.cc/path-of-the-wildebeest.7z

The bits are in little endian. Position 1 is little endian bit 0 of byte 0.

The 1,618,769,739 byte file compressed to 404,052 bytes.

(That file is the boolean map of visited positions.)

lirtosiast

23:19

Now that we've found this, we open the question: what's the relationship between the pattern of possible moves of an arbitrary leaper and its time to get trapped?

Deadcode

23:30

path-of-the-wildebeest on github

Pavel

@Deadcode Is that by you?

Deadcode

@Pavel Yes.

Davidebyzero = my alternate nick.

So what should a solution to the PPCG challenge return for steps > 12899744968? 12851850257 for all values there onward? And do the submitted solutions do that? :)

(Assuming enough memory and time for them to get there)

Jonathan Allan

@Deadcode I had already stated that if there was a trapping position the code behaviour afterward could be undefined

Deadcode

Ah yes, I see that.

@JonathanAllan Please edit it. My first comment was off-by-1.

I since then deleted the comment and made a new one

Jonathan Allan

23:45

K

Deadcode

It's position 12851850258

Jonathan Allan

ah just the square number?

Deadcode

And here I quoted my own mistake above :(

Yes, the step number is correct

Because that's actually 1-indexed in my code.

But I zero-indexed the position and did +1 every time printing it.

And forgot for the Trapped case.

(The github code already has that fixed.)

Jonathan Allan

thanks!

Deadcode

Welcome :)

I'm almost finished with a verification run now.

Oops, made my array too small in the github-committed version, somehow.

Oh

I had maxVisitedPos but what I actually wanted was maxExaminedPos

My result is correct because I was using a much larger array size than necessary

but I shrunk it for the commit

with no safety margin, because I got cocky

Jonathan Allan

23:53

you can always fix up the git hub code with another commit

Deadcode

I'm on it

Pushed a fix, and am currently testing it

oops, disregard that commit

There, pushed a fix that is probably correct. Now testing it.

feersum

I've replicated the result of stopping after the 12899744968th step.

Deadcode

@feersum Awesome. In what language?

feersum

C

Deadcode

My code or yours?

feersum

23:59

Mine.

Deadcode

Awesome.

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The Nineteenth Byte

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