explain xkcd - User contributions [en]

Talk:2048: Curve-Fitting

2018-09-19T18:14:36Z

162.158.92.184:

> House of Cards: Not a real method, but a common consequence of mis-application of statistical methods: a curve can be generated that fits the data extremely well, but immediately becomes absurd as soon as one glances outside the training data sample range, and your analysis comes crashing down "like a house of cards". This is a type of _overfitting_

I'm pretty sure it refers to the TV show house of cards, the dots representing the quality of the series increasing until Netflix renewed it a bit too much

I'm a little mystified by the alt-text. Cauchy and Lorentz both seem like mathematically capable people. What am I missing? [[Special:Contributions/172.69.62.226|172.69.62.226]] 17:46, 19 September 2018 (UTC)

: Google-Fu reveals that it's a continuous probability distribution. This isn't bad per se, but it is quite visually distinctive and also can be quite...concerning if the data set isn't one where probability should be an issue. [[User:Werhdnt|Werhdnt]] ([[User talk:Werhdnt|talk]]) 18:00, 19 September 2018 (UTC)

:: My own Google-Fu brought me to a page with this information: “The distribution is important in physics as it is the solution to the differential equation describing forced resonance, while in spectroscopy it is the description of the line shape of spectral lines.” (from here: https://www.boost.org/doc/libs/1_53_0/libs/math/doc/sf_and_dist/html/math_toolkit/dist/dist_ref/dists/cauchy_dist.html) [[User:Justinjustin7|Justinjustin7]] ([[User talk:Justinjustin7|talk]]) 18:09, 19 September 2018 (UTC)

To be honest, I'm a bit disappointed. I kinda expected a special comic with such a nice round number.. Been counting down since comic #2000... [[Special:Contributions/162.158.92.184|162.158.92.184]] 18:14, 19 September 2018 (UTC)

2045: Social Media Announcement

2018-09-19T17:17:02Z

162.158.92.184: /* Explanation */ Fixing incomplete tag

{{comic
| number = 2045
| date = September 12, 2018
| title = Social Media Announcement
| image = social_media_announcement.png
| titletext = Why I'm Moving Most of My Social Activity to Slack, Then Creating a Second Slack to Avoid the People in the First One, Then Giving Up on Social Interaction Completely, Then Going Back to Texting
}}

==Explanation==
{{incomplete|Too much focus on mastodon, not enough on the overall concept of the comic. Do NOT delete this tag too soon.}}

In 2018, especially after {{w|Facebook}} privacy abuses were revealed in the {{w|Cambridge_Analytica#Privacy_issues|Cambridge Analytica scandal}}, many individuals began seeking alternatives. The #deletefacebook hashtag peaked around April 2018, and in some communities, this type of "why I'm leaving Facebook" announcements were popular.

{{w|Mastodon (software)|Mastodon}} is a distributed, federated social network with microblogging features similar to {{w|Twitter}}. "Federated" means that there is one app hosted in many places, so users can choose a host that meets their needs, but everyone can still talk to each other, similar to email. Near the peak of #deletefacebook, mastodon became trending as a [https://motherboard.vice.com/en_us/article/783akg/mastodon-is-like-twitter-without-nazis-so-why-are-we-not-using-it twitter alternative with less nazis].

{{w|Wil Wheaton}} famously moved to Mastodon from Twitter, [https://news.avclub.com/wil-wheaton-on-quitting-social-media-i-don-t-deserve-1828743467 but was ultimately disappointed by the experience], because while Mastodon's community is generally less toxic, it does not yet have the tools to handle the kind of targeted harassment that a celebrity might face.

{{w|Microsoft}} has been buying up professional-themed social media platforms lately, such as {{w|LinkedIn}} and {{w|GitHub}}, intending to integrate them more fluidly with their enterprise software suite. Mastodon seems an unlikely target for an acquisition, since its decentralized nature means that one corporate entity can't control it, and the culture there is decidedly unprofessional as of this comic.

The title text presents an alternative approach by moving most social activities to the cloud-based proprietary team collaboration platform {{w|Slack (software)|Slack}}. After making his first workspace in Slack he suggests that he wishes to avoid the people invited, so he creates a second account and a new workspace. This also didn't last long and he stops interacting on social media entirely. As a result he has gone totally away from interacting on social media and has reverted to texting, i.e. sending {{w|sms}} using his phone as was the only possible way with the first mobile phones.

==Transcript==
:[Cueball sitting in front of a laptop typing.]
:Why I'm Quitting Facebook, Joining LinkedIn, Deleting My LinkedIn, Rejoining Facebook, Quitting Twitter, Getting Locked Out of Facebook, Moving to Mastodon, and Lobbying Microsoft to Take Over Mastodon and Merge It With LinkedIn: A Manifesto.

==Trivia==
In the original version of this comic, Cueball misspelled "Mastodon" as "Mastadon".

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Social networking]]

1266: Halting Problem

2018-07-15T11:30:55Z

162.158.92.184: /* Explanation */ Important addition to the first sentence of the explanation. The version before was imo misleading for people unfamiliar with the halting problem.

{{comic
| number = 1266
| date = September 18, 2013
| title = Halting Problem
| image = halting_problem.png
| titletext = I found a counterexample to the claim that all things must someday die, but I don't know how to show it to anyone.
}}

==Explanation==
In 1936 {{w|Alan Turing}} proved that it's not possible for an algorithm to decide whether an arbitrary program will eventually halt, or run forever. This was later called the {{w|Halting problem}} by {{w|Martin Davis}}. The official definition of the problem is to write a program (actually, a {{w|Turing Machine}}) that accepts as parameters a program and its parameters. That program needs to decide, in finite time, whether that program will ever halt running these parameters.

The halting problem is a cornerstone problem in computer science. It is used mainly as a way to prove a given task is impossible, by showing that solving that task will allow one to solve the halting problem.

[[Randall]], however, is providing a simpler solution. He implements his own code for the question ''"Does it halt?"'' which always returns "true", and directs us to think about the bigger picture.

From a '''physical''' perspective, according to our current understanding of physics, this is right. Given enough time, any program will halt. This is due to factors external to the actual program. Sooner or later, electricity will give out, or the memory containing the program will get corrupted by cosmic rays, or corrosion will eat away the silicon in the CPU, or the {{w|second law of thermodynamics}} will lead to the {{w|Heat death of the universe}}. Nothing lasts forever, and this includes a running program.

From a '''mathematical''' point of view, this is not true: a Turing machine will never have a hardware failure because it's not a physical machine. It's a theoretical construct, and it's '''defined''' mathematically, independent of any physical hardware. Similarly, ⅓ + ⅓ + ⅓ = 1 no matter what any physical hardware you are computing it on claims.

Another interpretation of [[Randall]]'s code is that the Program in the parentheses is actually being run whenever his function is called, as is consistent with some programming constructs. In this case, the function would wait until the program finishes and exits before returning "True". Therefore, [[Randall]]'s function is mathematically accurate. It does not solve the problem though, as it simply shifts the question to whether the function itself will ever halt.

From a '''practical''' point of view, there are of course times that a programmer would want to return "false", since some programs can be mathematically shown to run forever.

The title text further relates to this issue by claiming to have found a case where something need not die, but Randall does not know how to actually show it to anyone, because just the fact everyone will die sooner than it doesn't prove it will not die. The wording of the title text might also be a reference to {{w|Fermat's Last Theorem}}.

It should be noted that Randall's solution, barring its unsoundness, solves more than the halting problem in the form it is usually stated. The halting problem requires two parameters (a program and its parameters), while Randall's function only accepts one (the program). The question of whether a program halts for every input can be shown to be even harder to solve than the halting problem, meaning that even if a Turing machine had an additional instruction allowing it to check whether a program halts with given parameters, it still could not always confirm that a given program that halts for all parameters does so.

The code in this comic is written in {{w|pseudocode}}, to demonstrate the "algorithm" rather than an implementation in some existing programming language. The syntax resembles a mix of {{w|C (programming language)|C}} and {{w|Python (programming language)|Python}}.

==Transcript==
:[A short computer program.]
'''Define''' DoesItHalt(program):
{
'''return''' true;
}
:The big picture solution to the halting problem.

==Trivia==
*A similar useless computer program can be found here: [[221: Random Number]].

{{comic discussion}}
[[Category:Computers‏‎]]
[[Category:Programming]]