Gordon Linoff Updated 2025-07-16
Infinitely many SQL answers.
As mentioned at Ciro Santilli's Stack Overflow contributions, he just answers every semi-duplicate immediatly as it is asked, and is therefore able to overcome the Stack Overflow maximum 200 daily reputation limit by far. E.g. in 2018, Gordon reached 135k (archive), thus almost double the 73k yearly limit due to the 200 daily limit, all of that with accepts.
This is in contrast to Ciro Santilli's contribution style which is to only answer questions as he needs the subject, or generally important questions that aroused his interest.
2014 Blog post describing his activity: blog.data-miners.com/2014/08/an-achievement-on-stack-overflow.html, key quote:
For a few months, I sporadically answered questions. Then, in the first week of May, my Mom's younger brother passed away. That meant lots of time hanging around family, planning the funeral, and the like. Answering questions on Stack Overflow turned out to be a good way to get away from things. So, I became more intent.
so that suggests his contributions also take a meditative value.
www.data-miners.com/linoff.htm mentions he's an SQL consultant that consulted for several big companies.
LinkedIn profile: www.linkedin.com/in/gordonlinoff/ says he now works at the New York Times.
2021 Reddit thread about him: www.reddit.com/r/programming/comments/puok1h/a_single_person_answered_76k_questions_about_sql/ mentions that by then he had:
answered 76k questions about SQL on StackOverflow. Averaging 22.8 answers per day, every day, for the past 8.6 years.
Euler number Updated 2025-07-16
Go (game) Updated 2025-07-16
Companies are getting too much power to distort regulations and destroy privacy.
Taxes pay for the physical car roads, so why shouldn't they also pay for the "online roads" of today?
Other less simple ones that might also be feasible:
All of them should have strong privacy enabled by default: end-to-end encryption, logless, etc. Governments are not going to like this part.
And then if you ever forget a password or lose a multi-factor authentication token, you can just go to an ID center with your ID to recover it.
M,n,k game Updated 2025-07-16
Order of a differential equation Updated 2025-07-16
Order of the highest derivative that appears.
Bicycle tire sizes Updated 2025-07-16
Yes, Sheldon he has separate American and British English versions of pages!!!
For example, Kross bicycle (2017) had a Schwalbe tyre with markings:
42-622 (28 x 1.60, 700x40C)
When inflated, the tires were about 3.5cm wide as measured with a ruler.
And the Mavic A319 rim had markings:
622x19C
In this:
Chain rule Updated 2025-07-16
Here's an example of the chain rule. Suppose we want to calculate:
So we have:
and so:
Therefore the final result is:
Gradient Updated 2025-07-16
Takes a scalar field as input and produces a vector field.
Mnemonic: the gradient shows the direction in which the function increases fastest.
Think of a color gradient going from white to black from left to right.
Therefore, it has to:
  • take a scalar field as input. Otherwise, how do you decide which vector is larger than the other?
  • output a vector field that contains the direction in which the scalar increases fastest locally at each point. This has to give out vectors, since we are talking about directions
Graphene Updated 2025-07-16
A single layer of graphite.
Green fluorescent protein Updated 2025-07-16
The 3D structure of GFP is so cool. It is so clearly a bottle with a fluorescent bit well isolated right in the middle. Like a little lamp.
grep Updated 2025-07-16
If you are a programmer, grep becomes a verb: "to grep" means "to search text files", much like "to Google" means "to search random stuff online".
Grinding for software interviews Updated 2025-07-16
If your kids are about to starve, fine, do it.
But otherwise, Ciro Santilli will not, ever, spend his time drilling programmer competition problems to join a company, life is too short for that.
Life is too short for that. Companies must either notice that you can make amazing open source software projects or contributions, and hire you for that, or they must fuck off.
Companies must either notice that you can make amazing projects or contributions, and hire you for that, or they must fuck off.
Group extension problem Updated 2025-07-16
Besides the understandable Wikipedia definition, Video "Simple Groups - Abstract Algebra by Socratica (2018)" gives an understandable one:
Given a finite group and a simple group , find all groups such that is a normal subgroup of and .
In particular, this is hard because you can't just take the direct product of groups to retrieve the original group: Section "Relationship between the quotient group and direct products".
Group homomorphism Updated 2025-07-16
Like isomorphism, but does not have to be one-to-one: multiple different inputs can have the same output.
The image is as for any function smaller or equal in size as the domain of course.
This brings us to the key intuition about group homomorphisms: they are a way to split out a larger group into smaller groups that retains a subset of the original structure.
As shown by the fundamental theorem on homomorphisms, each group homomorphism is fully characterized by a normal subgroup of the domain.
Bilinear map Updated 2025-07-16
Linear map of two variables.
More formally, given 3 vector spaces X, Y, Z over a single field, a bilinear map is a function from:
that is linear on the first two arguments from X and Y, i.e.:
Note that the definition only makes sense if all three vector spaces are over the same field, because linearity can mix up each of them.
The most important example by far is the dot product from , which is more specifically also a symmetric bilinear form.

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