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 Discussion on answer by Avery: Were t…

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anonymous
Dec 24, 2019 12:46
@ Zonata That's not entirely accurate. Carbon capture and sequestration technology does exist, but it hasn't been scaled up to the point to remove atmospheric carbon dioxide yet. Best we can do at an industrial scale requires connection to a point source.
 

 Discussion on question by K Dog: Did …

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anonymous
Aug 30, 2019 16:32
Possible duplicate of Do human activities contribute to climate change?
 

 Discussion on question by Vladhagen: …

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anonymous
Jun 7, 2019 01:38
How do they determine one credit versus three credits when planning classes? From the description it really doesn't seem like there are enough contact hours to justify three credits.
 

 Discussion on question by Rebecca J. …

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anonymous
Nov 13, 2018 03:56
@Headcrab Typically I simply address them as "the reviewer" as in, "The reviewer raises an interesting point. However, in section two I address this by ...."
 

 Discussion on question by LilyOfTheEa…

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anonymous
Oct 19, 2018 20:13
@Kimball You mean the Baader-Meinhof phenomenon?
anonymous
Oct 19, 2018 20:13
@Scientist I'm wondering the same thing in terms of dress and it's really hard to say without more detail. I wonder if the OP might have inadvertently become a bit of a tread setter on campus, if only because they would stand out more than others. On my own campus (rural university) I've noticed the same sort of behavior taking place (ex., male faculty wearing sport coats to lecture after a male lecturer wears them on a regular basis).
anonymous
Oct 19, 2018 20:13
What part of Europe? Some of the advice for handling things is going to be cultural and this site tends to have a bit of an American bias.
 

 Discussion on question by matt_black:…

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anonymous
Jul 24, 2018 02:23
... there is a lot of criticism aimed at them as a result when you start looking at things with a narrow focus.
anonymous
Jul 24, 2018 02:22
Likewise, something like ecological footprints can be used to set national level agendas and can very coarsely be broken down to account for national contributions. Once you know that national contribution you can then proceed to say something like, "There's not much you can do other than diplomacy" or "Improving public transportation will reduce the countries carbon footprint." However, the understanding with the sustainability community is that these are really coarse measures and ...
anonymous
Jul 24, 2018 02:20
Think along the lines of the GDP - it has lots of problems and is actually a really bad measure of things, but it gets used a lot since it is fairly easy for people to understand and policy measures to manipulate it are also fairly easy to understand as well.
anonymous
Jul 24, 2018 02:18
So a couple quick thoughts since a lot of my research in based on sustainability, but pretty much all of the measures have one problem or another for a long list of reasons. At a global level we have some that are "good enough" to give really coarse guidelines for policymakers though a long with a quick explanation of what they mean.
 

 Discussion on question by rjzii: How …

Imported from a comment discussion on cs.stackexchange.com/que...
anonymous
Jun 21, 2018 05:22
Cool, I'll take a look at it.
anonymous
Jun 20, 2018 17:36
Sounds good, thanks!
anonymous
Jun 20, 2018 17:34
I'm thinking I'll be throwing a question over on SE about turning - will link it here when I do.
anonymous
Jun 20, 2018 17:33
Looks like 1M peaks at around 2GB, so 3GB might be workable
anonymous
Jun 20, 2018 17:32
KDTree
2018-06-20T13:19:56.865: Starting simulation...
2018-06-20T13:24:24.902: 100 of 870
2018-06-20T13:29:51.126: 200 of 870
anonymous
Jun 20, 2018 17:31
Most of my reading about KDTrees has been that 1) they are really hard to tune the implementation of and when you've got a lot of CRUD happening it get's even worse. The entities are uniformly distributed too, so no clumping which drives up the odds of the worse case O(n).
anonymous
Jun 20, 2018 17:30
In the lab we have stupid amounts of RAM though and they already know that the 10M runs will only take place there.
anonymous
Jun 20, 2018 17:29
I can do that with the computers in the lab, but my workstation only has 8GB.
anonymous
Jun 20, 2018 17:29
There's some weird stuff in the code as well to try and get around that - looking up where an entity is in the hashmap is basically a free operation - I'd have to hunt in YourKit for the method. That also gives us other occupietns of the same location for free.
anonymous
Jun 20, 2018 17:28
Correct.
anonymous
Jun 20, 2018 17:27
This is the code that I've been spending time turning:
Partitioned Object2ObjectOpenHashMap
2018-06-20T13:07:50.008: Starting simulation...
2018-06-20T13:10:05.644: 100 of 870
2018-06-20T13:13:10.645: 200 of 870
anonymous
Jun 20, 2018 17:27
I'm running some metrics on the KDTree to share to satisfy everyone, but the KDTree is running much slower than the hashmap strategy.
anonymous
Jun 20, 2018 17:26
Yeah, this is all written in Java.
anonymous
Jun 20, 2018 17:06
I wish it was just as simple as keeping things in L3 cache... but I don't have have 136 MB of L3 at my disposal. :D
anonymous
Jun 20, 2018 17:06
@JimmyJames What I mean is that even after spending time turning the code, using fast libraries (ex., fastutil, dsiutils) there's still a lot of math going on that takes time to run. I've been spending time playing around with object creation because the GC starts to cause problems after things have been running too long.
anonymous
Jun 19, 2018 23:14
Before I revise the question, does what I said here in chat clarify things for you?
anonymous
Jun 19, 2018 23:12
Plus, I already pointed out in the question that O(c) < O(log n) in this case and since N is only getting bigger I don't see that flipping the other way any time soon. Plus, there's always the chance that we can bump into the O(n) worse case for CRUD operations.
anonymous
Jun 19, 2018 23:10
@D.W. I agree, but given that @JimmyJames has been pushing them hard, the onus is kind of them to either give me a way to evaluate k-d trees on the back of an envelope, or just my judgement that they aren't appropriate for this particular application. I could just as easily say that R-trees would be better... but without a logical grouping it doesn't make sense to use them.
anonymous
Jun 19, 2018 22:29
However, my google-fu seems to be failing me over on ACM and IEEE Xplore since I'm either getting not hits or too many irrelevant hits. Some of the language overlaps with GIS as well which doesn't seem to help me very much, since there really isn't any way to index the entities.
anonymous
Jun 19, 2018 22:20
In this case r is variable, although I might be able to throw some analysis techniques at it to come up with some sort of mean r as a starting condition. There's also some algorithm optimizations I can do, but those might be coding details as opposed to the CS.
anonymous
Jun 19, 2018 22:18
It looks like one simple strategy is limit the bin size to the the size of your search radius, but that's only effective when r is fixed.
anonymous
Jun 19, 2018 22:16
The s used to partition the 3D lattice is the really insidious part because I don't know how to explain that better than I already have. However, the link in the question takes you to a slide deck for a presentation that discusses spatial partitioning strategies at a really high level.
anonymous
Jun 19, 2018 22:14
@D.W. Projecting a movement means that the entity calculates a movement to a new position and uses that location to search for matching entities. If a match is found f() is called which will destroy one or more entities and create one or more entities. If a match is not found than the location of the entity is updated to the new location. Realistically it's a bit of a micro-optimization, but it's low hanging fruit to avoid the update if we are unsure if the entity will continue to exist.
anonymous
Jun 19, 2018 22:09
@JimmyJames I understand the point about array traversals just fine. However, you haven't done anything to convince me that what you are asserting will apply in this situation. Plus k-d trees are only O(log n) in the average case so I could end up with a model that has a the worse case O(n) insertions often enough to slow everything down. The really insidious part of this model is the fact that everything is always moving and inserts-deletes are happening on a regular basis.
anonymous
Jun 19, 2018 18:19
If there is an approach that can handle fast searches as well as constant updates to the data structure I'm open to hearing about it. However, based on all of the reading I've been doing so far, partitioning seems to be the best approach to things.
anonymous
Jun 19, 2018 18:19
@JimmyJames It's actually a real modeling problem - I work within the CS&E domain - and in terms of real numbers, for 1M entities it takes about 30 minutes to converge and that is without any searching being done. The radial search is a new feature and the existing data structures didn't even support it. It doesn't have to be $O(1)$ for CURD operations, but that $O$ needs to be as low as possible since typically each iteration of the for loop will have either an update or multiple deletes and inserts.
anonymous
Jun 19, 2018 18:19
@JimmyJames Not sure if you caught the updates to the question, but the starting conditions are 10M entities and that can double or triple during execution. Sure for small $N$ I'll whip up a bubble sort knowing that quick sort is better, but my time is more valuable in those cases and the time difference is minuscule. In this case though, the model already take around 30 minutes to converge, I'd rather not do anything to make it take longer. The whole point of this exercise is to speed things up.
anonymous
Jun 19, 2018 18:19
@DocBrown D'oh! That link isn't in the question any more though, the text of the question should be fairly on point and I updated the psudo-code. In my case though there are multiple entity types, each of which can have their own $r$ value. The $r$ should be stable for the duration of the for loop though.
anonymous
Jun 19, 2018 18:19
@DocBrown Also, in the context of my specific problem, I'm not even sure I could determine an $r_{max}$ since there is some stochasticity involved with it as well. However, I'm trying to keep the question fairly generic since I've seen similar problems pop up elsewhere.
anonymous
Jun 19, 2018 18:19
@DocBrown I suppose it wasn't entirely clear before, but $r$ is variable. As such, any binning strategy based upon $r$ will not work. Hence the need for partitioning space to avoid having to search all entities.
anonymous
Jun 19, 2018 18:19
@D.W. 1) The comments are obsolete because the question was edited on SE before it was migrated here. 2) Give me a little bit to mathematically formalize the problem, I tend to work more in a CS&E space so some of my notation is a bit rusty. 3) Other nearest neighbor approaches were rejected because the data set as a whole updates every time step (i.e., everything is moving).
anonymous
Jun 19, 2018 18:19
@D.W. 1. All of the comments are obsolete now. 2. I'm not too worried about the implementation details, but I do remember from CS classes that there are some analytical approaches we can apply that help for both the hash maps and determining partition sizes.
 

 Discussion on question by MathAnon: S…

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anonymous
Jul 30, 2017 20:19
@NeilMeyer The OP says nothing to imply that the are ashamed of using a dating app, their questions is of a professional nature. Furthermore, there is absolutely nothing there to warrant speculation on their self-confidence. Quite frankly even remotely suggesting that they might need therapy for wanting to engage in a very normal human actively is offensive.
 

 Discussion on question by DavePhD: Wh…

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anonymous
Jun 26, 2017 16:58
@eykanal The question might need a split and full re-write. Reading the article, Is suspect that it was being written for longer than the SE post was.
 

 Discussion on question by Azendale: I…

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anonymous
May 30, 2017 07:04
Also, you still need your transcript in those cases since the transcript is what the school uses to authenticate the diploma. Why they can't just use the transcript, eh, who knows.
anonymous
May 30, 2017 07:04
@Jeffε I'm guessing you didn't catch it, but I mentioned Apostille copies for a reason. Some counteries accept the transcript, others want a copy of the diploma itself. Korea is one (lazy source: kimchiteaching.wordpress.com/2012/02/08/…) and I've heard of a couple Eastern European countries.
anonymous
May 30, 2017 06:58
@Jeffε
anonymous
May 29, 2017 19:17
@JeffE That's not entirely accurate. Your diploma is a legal document, but only has very limited uses. The only one that I can think of is that a lot of foreign countries want a Apostille copy of your diploma to verify your credentials for work visas.
 

 Discussion on question by Andrew Grim…

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anonymous
Apr 29, 2017 14:42
@sumelic Systemic and institutionalized both have standard terms in the literature, so those shouldn't be a problem.