explain xkcd - User contributions [en]

2142: Dangerous Fields

2025-01-26T23:27:27Z

162.158.167.176: /* Explanation */

{{comic
| number = 2142
| date = April 26, 2019
| title = Dangerous Fields
| image = dangerous_fields.png
| titletext = Eventually, every epidemiologist becomes another statistic, a dedication to record-keeping which their colleagues sincerely appreciate.
}}

==Explanation==
This is a graph of fields of study, ordered by how likely one is to die because of something that that field studies, with mathematics being the least dangerous and gerontology being the most. Gerontology, the scientific study of old age, is shown as much more dangerous than the other fields, so it is far on the right side of the graph. The joke is in exploring what the words "risk" and "danger" really mean in this context — studying volcanoes is likely to put you in dangerous environments, and the volcanologist can be said to have "survived" if they later die of old age. Conversely, studying aging doesn't put you at more risk of aging than the general population, but there is no "surviving" from this perspective, only the chance of dying early from something else.

===Fields===
*{{w|Mathematics}} is such a pure non-physical field that the probability of it being the direct cause of death is extremely low. The study of it might cause death through workplace disputes or absent-mindedly wandering in front of traffic while pondering (as in [[356: Nerd Sniping]]). Famously (though likely apocryphally) {{w|Hippasus}} was thrown overboard a ship by {{w|Pythagoras}} for demonstrating irrational numbers. {{w|Archimedes}} was killed for not following an invading soldier's command because he was wrapped up in his own thoughts trying to solve a geometry problem.

*{{w|Astronomy}}, the study of stars and space. Astronomy is slightly more dangerous than mathematics, though, since it studies physical objects instead of abstract concepts. In addition to meteor or asteroid impacts, astronomical phenomena that might cause death include solar flares, nearby supernovae, distant magnetar quakes, a solar nova (the likelihood of which will increase over the next billion-odd years), perturbations in earth's orbit, increased or decreased solar radiation, and alien invasion. Given that the density of magnetars and potentially hostile alien civilizations in the stellar neighborhood is completely unknown, and not all past mass extinctions are explained, this one might be misplaced a bit. Although these are all rare events, just one could kill all living and potential future astronomers. That non-astronomers would also be affected seems poor consolation. While astronomers do not study aliens, as such—that would be exobiology—some have sought evidence of alien activity.

*{{w|Economics}} is the study of markets. Markets can kill you by depriving you of goods and services you need to survive. Goods can become unavailable (e.g., cartels, embargos) or unaffordable (through job loss, inflation), in depressions or recessions. The study of such markets usually does not involve great risk, unless the markets are illegal (e.g., illicit drug markets), the economy being studied has put people under great stress, or one's findings are really unpopular.

*{{w|Law}} in this context refers to the rules people have to follow in society, and given the nature of laws (civil and criminal), the odds that your death is related to law is usually low. Possible causes of death more-or-less directly related would include prosecution for a capital crime, persecution under legal authority (such as being killed by an officer of the law), attack by a guard, or for lack of medical treatment, while incarcerated, or death by exposure after expulsion from one's repossessed or otherwise legally confiscated home. However, when large groups of people are dispossessed, or have the protection of law removed, casualties can be quite high. For instance, the {{w|Partition of India}} in 1947 resulted in 200,000 to 2 million deaths. The laws of the {{w|Great Leap Forward}} contributed to the starvation of tens of millions of Chinese, disproportionally many of them lawyers and law professors. Perhaps most ironically, a lawyer who committed a capital crime in a country that practices capital punishment (such as the United States, China, or Iran), and was executed for it would be directly killed by the thing they study. In 2000, approximately 300,000 died from war and collective violence.

*{{w|Criminology}} is very similar to law, but is the study of crime, meaning it's more dangerous than just "law." Criminologists may be directly involved with criminals in the course of their studies, increasing their exposure to potentially life-threatening behavior. There were 520,000 deaths from violence (excluding war, suicide, and accidental or incidental deaths resulting from criminal activity) in 2000.

*{{w|Meteorology}} is the study of weather. Encountering powerful weather events such as hurricanes, tornadoes, blizzards, floods, and thunderstorms brings the distinct possibility of injury and death. Curiosity to see a storm in person, or (if working for television news) exposing yourself to the weather event in order to file a report, may expose you to lightning, wind-blown projectiles, cold, water, etc., any of which can negatively affect your survival. Less dramatic weather also kills — hot weather can lead to heatstroke and dehydration. Adverse weather events kill about 100,000 to 200,000 annually.

*{{w|Chemistry}} is the study of chemicals and reactions of those chemicals. Since, under terrestrial conditions, everything is made up of chemicals (and chemists often use especially reactive or dangerous chemicals), the likelihood of a chemist's death being caused by chemistry (e.g., explosions, poisoning, chemical burns, suffocation) is not insignificant. Unintentional poisoning is identified as the cause of death for about 200,000 people a year, chemical assisted suicide kills over 300,000 yearly. Many other causes of death, such as snakebite (100,000), drug and alcohol disorders, some respiratory disorders, and cancers are more or less directly caused by chemicals.

*{{w|Marine biology}} is the study of ocean life. Many marine creatures are venomous, many are very large. Death could result from storms, boat accidents, drowning, diving accidents, exposure to pathogenic bacteria, toxins (such as those produced by cone snails, and "red tide" dinoflagellates), allergies to shellfish, or water pollution, in addition to such perhaps more obvious (but overwhelmingly rarer) risks as shark attacks. About 360,000 people die of drowning annually. Unprovoked shark attacks kill an average of 6 people annually.

*{{w|Volcanology}} involves the study of {{w|volcanoes}}, {{w|lava}}, and {{w|magma}}, with obvious risks to the scientists studying them in the field. Volcanoes have killed an estimated average of 500 people per year; most deaths result from remote effects, such as tsunamis and climate disruption. At least 67 scientists have been killed in volcanic eruptions, as of 2017.

*{{w|Gerontology}} involves the study of aging, and of growing old in general. As (to general knowledge) everyone has to this point been observed to age and eventually die,{{Citation needed}} those who study gerontology are not immune to dying of old age even if they evade all the other possible causes of death — thus making it the most likely among all shown fields. A gerontologist still can die from something else first, but without the inherent risk factors of other professions such as active volcanoes or underwater diving, they're more likely to survive to retirement and thus meet their death of old age.

The title text is about {{w|Epidemiology}}, the study of health and disease conditions in populations. In the event of an epidemic, there is a strong chance that epidemiologists in the search for the cause, transmission, and treatment will be exposed and become victims of the disease in their own right. However, the title text refers more broadly to the role of epidemiology in maintaining detailed statistical records of diseases and other causes of death, such that eventually any epidemiologist (whatever the cause of death) will become one of their own statistics.

==Transcript==

:[A line chart is shown going from left to right with two arrows on either side. On the line are ten dots spread out unevenly from close to each end. The first four dots are clustered together on the left side. Then follows 5 more dots unevenly spaced, all to the left of center. On the far right of the line, near the end, there is one dot. Beneath each dot, there goes a line down to a label written beneath each line. Above the chart, there is a big title and below that is an explanation. Below that again, there is a small arrow pointing to the right with a label above it.]
:<big>Probability that you'll be killed by the thing you study</big>
:By field

:[Arrow pointing right, labeled:]
:More likely

:[Labels for the ten dots from left to right:]
:Mathematics (0 pixels from first field, 0.00% of overall range of fields)
:Astronomy (9px, 1.35%)
:Economics (16px, 2.40%)
:Law (22px, 3.30%)
:Criminology (77px, 11.56%)
:Meteorology (96px, 14.41%)
:Chemistry (156px, 23.42%)
:Marine Biology (166px, 24.92%)
:Volcanology (206px, 30.93%)
:Gerontology (666px, 100.00%)

{{comic discussion}}

[[Category:Charts]]
[[Category:Rankings]]
[[Category:Science]]
[[Category:Scientific research]]

3026: Linear Sort

2024-12-18T17:16:48Z

162.158.167.176:

{{comic
| number = 3026
| date = December 18, 2024
| title = Linear Sort
| image = linear_sort_2x.png
| imagesize = 385x181px
| noexpand = true
| titletext = The best case is O(n), and the worst case is that someone checks why.
}}

==Explanation==
{{incomplete|Created in Θ(N) TIME by an iterative Insertion Sorter working on a multidimensional array - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A common task in programming is to sort a list, a list being a collection of related elements of data that are stored in a linear fashion. There are dozens of algorithms that have been created through the years, from simple to complex, and each has its own merits with regards to how easy it is to understand / implement vs. how efficiently it operates on the data.

The efficiency of an algorithm is measured in terms of O(), commonly referred to as "Big-O", which classifies the amount of time needed to execute the algorithm with respect to the size of the data. Specifically, the Big-O assignment describes the change in execution time when the size of the data set changes (typically, when it doubles). There are various measures of efficiency, such as:
<ul><li>O(1) - Constant, which means the execution time is independent of the size of the data</li>
<li>O(n) - Linear, which means the execution time varies in direct proportion to the size of the data</li>
<li>O(n log n) - "n log n", usually assigned to the fastest sorting algorithms. Execution time is higher proportionally compared to O(n).</li>
<li>O(n2) - Quadratic", meaning the execution time is proportional to the square of the size of the data.</li></ul>
It can be proven that the best general-purpose sorting methods are "n log n". Thus, a sorting algorithm in linear time does not actually exist.

In computer science, the complexity of a problem can be described using {{w|Big O Notation}}. Operations generally take longer when they act on more elements (notated as "n"). A linear algorithm would be very simple: each element would take a short amount of time on its own, so the time it takes would be a multiple of the size of the list. For instance, if it takes one second to look at a picture, it would take ten seconds to look at ten pictures. So "look at a list of pictures" is a linear operation and would be described as having complexity O(n).

Sorting is more complex. The time it takes to sort a list of items grows quickly as you add more items to the list. The complexity of sorting algorithms generally ranges from O(n^2) to O(n*log n). For example, one way to sort is to look at all the values to find the first item, then look at all the values to find the second item, and so on until you've positioned every item in the right place. If "looking at a number" takes one second, then you could sort a list of 2 numbers in 4 seconds: look at both numbers, then look at them a second time. Sorting 3 numbers would take 9 seconds: look at all 3 numbers 3 times to find the right position. Sorting a deck of cards this way would take 52*52 seconds = about 45 minutes. You can probably read a card more quickly than that, but the point is that the amount of time it takes to sort a list grows faster the more items you are looking at. This is not the most efficient way to sort, but it gets the job done.

The 'linear' sort here uses the less efficient {{w|merge sort}} rather than linear taking linearithmic, or O(n * log n) time. It does not matter, however, because it `sleep()`s for 1e6 (1 million) seconds, i.e. more than 11 days, per item in the list by sleeping for that length of time minus the time it actually took -- converting it by brute force to linear time that is so slow that it will not overcome the O(n * log n) term for large datasets. It's linear because it's guaranteed to take a million seconds for every element in the list (regardless of how long that actual sort really took); double the list size doubles the number of millions of seconds it takes. No matter how inefficient the actual sort method is, it is very unlikely it would take longer than a million seconds per element (unless some super inefficient algorithm is used, e.g. BogoSort). It should be noted that for sufficiently large lists, Mergesort will take longer than the 1e6 seconds, at which point the sorting algorithm will stop being linear anyway. However, this issue will only arise at impractically huge lists (though with the extreme lengths of this proposed sorting algorithm, one could argue any length of list is impractically huge).

The title text refers to the {{w|Best, worst and average case|best and worst case}} of the sort. The joke is that by making the "best case" linear so bad that it is worse than the worst case, the real best case is someone just trusting that a "linear sort" is best and not questioning why it's so slow. The worst case now is someone investigating how it's possible a sort could be taking a million seconds per element and discovering the deception in the code.

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}
:[The panel shows five lines of code:]
:function LinearSort(list):
::StartTime=Time()
::MergeSort(list)
::Sleep(1e6*length(list)-(Time()-StartTime))
::return

:[Caption below the panel:]
:How to sort a list in linear time

{{comic discussion}}

[[Category:Programming]]

Talk:3020: Infinite Armada Chess

2024-12-05T20:21:46Z

162.158.167.176:

Did I do well? Added a very very basic explanation. [[Special:Contributions/172.68.147.132|172.68.147.132]] 04:25, 5 December 2024 (UTC)

Well, yes but I wonder if just one tiny fix is needed. If you replace the white side with a simplyfied artillery tower, you reinvented space invaders.{{unsigned ip|172.71.160.70|04:57, 5 December 2024 (UTC)}}

I was personally hoping for an explanation of the Infinite Armada thing, and I feel like a link to the TV Tropes page doesn't really. Explain that at all. So I would love a bit of an expansion on that part! Just want to be sure I didn't miss some reference or something. [[Special:Contributions/172.68.23.91|172.68.23.91]] 05:48, 5 December 2024 (UTC)
: Likewise. I get the comic, but I assumed the 'armada' part was a reference that I just did not get. But it seems it is just a word choice. [[Special:Contributions/172.71.102.105|172.71.102.105]] 09:39, 5 December 2024 (UTC)
:: The only "Infinite Armada" reference I can think of is ''[https://en.wikipedia.org/wiki/Star_Wars:_Knights_of_the_Old_Republic Star Wars: Knights of the Old Republic]'', which kind of makes sense because if you have a Star Forge to make chess pieces with, why wouldn't you make them all queens? [[Special:Contributions/162.158.167.159|162.158.167.159]] 18:47, 5 December 2024 (UTC)

I think that since the error was "out of bounds", not "out of memory", it's referring to indexing outside of the region of memory that the program allocated to deal with the board. This would happen since instead of addressing rank 1..8, you could address rank 9, 10, 0, or -1. Unless bounds checking is performed when converting the board coordinates into linear array indices, you'd get an out-of-bounds error (or worse, succeed in reading or modifying memory that you weren't intending to). --[[Special:Contributions/172.71.30.253|172.71.30.253]] 05:45, 5 December 2024 (UTC)
:It was "Out of Bounds memory access". That means it was trying to access a memory address that was out of the bounds of the computer, as if it were trying to access the ω-th index of the board array, which would put it out of the memory range of any computer [[User:Firestar233|guess who]] ([[User talk:Firestar233|if you want to]] | [[Special:Contributions/Firestar233|what i have done]]) 06:15, 5 December 2024 (UTC)
:: There is no hint that the bounds are those of the computer, the simplest explanation really is that the bounds are those of an array. The error message does come up. In addition, to try to access the memory at the ω-th index, you would need to construct the ω-th index itself first (which would fail or not terminate) [[User:Jmm|Jmm]] ([[User talk:Jmm|talk]]) 07:01, 5 December 2024 (UTC)
::: The specific message, "RuntimeError: Out of bounds memory access", is a WebGL error issuing from its WASM cross-platform browser implementation. This implies to me that an attempt to render an infinite chessboard failed in a fairly trivial way, because of a poor implementation. It's very unlikely that there had been a problem with the [https://github.com/official-stockfish/Stockfish/tree/master/src Stockfish playing algorithm] yet, which would have failed with a different message if it ran out of memory, such as "Killed", which is all that shells like Bash print when one of their job processes is killed by the kernel's OOM killer, or by anything else for that matter. [[Special:Contributions/172.70.215.21|172.70.215.21]] 12:58, 5 December 2024 (UTC)

Is this a reference to [https://youtu.be/rav29N0-h2c infinite chess by Naviary?] [[User:HaruruChanDesu|HaruruChanDesu]] ([[User talk:HaruruChanDesu|talk]]) 11:21, 5 December 2024 (UTC)

"it does not really need to consider the infinitely many pieces" => a chess Engine would need to consider the infinitely many pieces (or have a way to abstract them), even if some pieces are currently stuck because the engine recursively evaluates moves and counter-moves (i.e. evaluates the game up to some depth).

Can someone explain the linked joke with all the extra queens? I don't understand why it's a bad position. [[Special:Contributions/172.69.59.126|172.69.59.126]] 16:49, 5 December 2024 (UTC)
:Knight to d6. [[Special:Contributions/162.158.167.175|162.158.167.175]] 17:09, 5 December 2024 (UTC)
::...is checkmate by black. White can't capture the knight with either of the two queens that attack it because they're both pinned, by black's bishop and rook. (And we know it's black's turn to move because the colored squares indicate white just moved.) [[User:DKMell|DKMell]] ([[User talk:DKMell|talk]]) 17:54, 5 December 2024 (UTC)

== Hit me up when this becomes real. ==

I would like to try this out. [[User:CalibansCreations|'''Caliban''']] ([[User talk:CalibansCreations|talk]]) 12:29, 5 December 2024 (UTC)
:It should be easy enough. You will rarely get the queens out in play from deep in the array. So maybe just put two chess boars together and put some placeholder in for queens in the extra fields. If ever a queen in the bottom row is moved, place extra queens that can now be moved into the 2-3 squares that would be outside the board...--[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 12:39, 5 December 2024 (UTC)
:It might be something one could set up in Infinite Chess, although having limits on the chessboard may be difficult. [[Special:Contributions/172.68.150.67|172.68.150.67]] 14:01, 5 December 2024 (UTC)

: Here's a finite approximation in ChessCraft: https://www.chesscraft.ca/design?id=5KM4 [[User:Promethean|Promethean]] ([[User talk:Promethean|talk]]) 15:37, 5 December 2024 (UTC)

While I understand how to play chess, I don't get the bit about "having a bunch of queens doesn't go very well". At first glance, the linked chess layout looks pretty solid. Can someone please enlighten me? Also, what does the TV Tropes link about Title Drop have to do with Infinite Armada, aside from that being the title of the comic? [[Special:Contributions/172.70.230.77|172.70.230.77]] 13:10, 5 December 2024 (UTC)

:: ... Nd6. [[Special:Contributions/172.70.91.246|172.70.91.246]] 13:31, 5 December 2024 (UTC)

::: Ah, thanks. Moving the knight there puts the king in check, and moving either queen to take it exposes the king to the bishop or rook, so checkmate. [[Special:Contributions/162.158.63.38|162.158.63.38]] 15:05, 5 December 2024 (UTC)

::::You are assuming that the opponent makes no moves while you spend at least three moves advancing your knight. Looks like either side can draw by always moving the king backwards whenever a queen has moved and made a hole he can move to and otherwise trying to make a new, deeper hole. Eventually he gets so far back that any attack turns into an infinite sequence of queens taking each other, with the attacker only having file attacks while the defender can retake from a rank, file, or diagonal. Any time the attacker breaks off the infinite sequence of queens taking each other to set up something else, the defender takes advantage of the break to move the king deeper and put more queens in front of him or to create more empty spaces to sidestep into when attacked. To me, this looks like a certain draw. [[Special:Contributions/172.69.33.252|172.69.33.252]] 16:21, 5 December 2024 (UTC)

You might be able to get the developer of fairy stockfish ( https://fairy-stockfish.github.io/ ) to add this if you ask nicely. I have seen them add several reader requests. [[Special:Contributions/172.70.211.143|172.70.211.143]] 15:46, 5 December 2024 (UTC)

Could this be a reference to the meme about "eating an infinite armada of pizza"? The wording seems too similar to be a coincidence. [[Special:Contributions/172.70.114.46|172.70.114.46]] 14:46, 5 December 2024 (UTC)

Would this guarantee a draw between two competent players who'd played the variant before, or would there be more nuance to it than there appears to be?

Can someone explain the linked joke with all the extra queens? I don't understand why it's a bad position. [[Special:Contributions/172.69.59.125|172.69.59.125]] 16:48, 5 December 2024 (UTC)

The explanation of the linked joke is that the king appears safe at first glance, but in reality there is a simple move that wins the game for black. Moving the black knight to the top left corner of the queen square checks the king. The king cannot move to escape. Two queens are in position to take the knight and save the white king, but both of those moves expose the king to attack from other black pieces (the rook or the bishop).

Wow. Not only did White give Black a mate in one, they also blundered a mate in one. [[Special:Contributions/162.158.167.176|162.158.167.176]] 20:21, 5 December 2024 (UTC)

Talk:3020: Infinite Armada Chess

2024-12-05T20:21:34Z

162.158.167.176: