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2:31 AM
@Feeds no way! I asked this question years ago, and my sister and I tried to figure it out
 
 
3 hours later…
 
8 hours later…
2:02 PM
@NathanMerrill no you're right, I completely mixed up the two things: I am interested in the fewest number of evaluations of the function. The algorithm itself could be arbitrarily involved.
but lets say there is an O(n) algorithm, then we obviously cannot have O(n^2) evaluations:)
 
3:02 PM
well, I believe that my algorithm then will work
You can figure out the relative location of all points in O(n)
and then use a standard algorithm to figure out the closest points
Wikipedia says that this is O(n) (if you allow randomness as well as a constant-time floor function)
 
I see, this works if the number of dimensions is known.
Now I'm really curious to know what happens for general metric spaces :)
 
I'm guessing that you can triangulate in the Nth dimension using N other points?
 
@NathanMerrill yes
Hm, cannot find anything about this problem in general metric spaces
 
3:40 PM
hmmm...actually, triangulation only works if the points aren't on the same line
 
Another related question: Lets say we have some points in R^n how can we (efficiently) determine the most isolated point? (a point with the greatest distance to its closest neighbour)
 
(or plane for the 4th dimension, etc)
 
@flawr That's effectively minmaxing on distance, isn't it?
Or rather, maxmining. Finding the maximum of minimums.
 
@El'endiaStarman I'd say maxmining :)
Right
 
Y'know, this is actually a really good point. An AI in control of unstoppable swarms of killer robots is just as scary when itself controlled by a human.
 
4:20 PM
....there was a youtube video about this
like, a corporation that sold these death bots
and people could buy them and choose anybody to die, and it was virtually anonymous
 
5:16 PM
1
Q: How to efficiently compute the most isolated point?

flawrGiven a finite set $S$ of points in $\mathbb R^d$, how can we efficiently compute a "most isolated point" $x\in S$? We define a most isolated point as by $$x = \arg\max_{p \in S} \min_{q \in S \setminus \{p\}} d(p,q)$$ (I used the $x=\arg\min$ notation even though it is not necessarily unique...

 
5:37 PM
There are really four types of neighbors here:
1. The best friends (Nearest neighbor)
2. The loner (Most isolated point)
3. The social butterfly (Smallest distance to furthest point)
4. The enemies (Largest distance to furthest point)
 
 
3 hours later…
9:01 PM
^ recommend watching: Even if you don't know CD there are some nice parodies of channels you most certainly know :)
 
9:58 PM
I've been watching a bunch of his videos recently :P
I'm not sure why I like him.
but he's great
 

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