Thanks. This is something!
2,496 karma · joined September 28, 2015
These notes contain the definition of various chain complexes and groups (co-homology/homotopy) that are in-principle computable. However, I have not seen this being efficiently applied somewhere, and not been able to come up with interesting applications myself. Topics I have considered are:
1. Triangulation of solutions of equations (for e.g. homology computations) does not seem to be very popular, at least in dimension >3. I suspect this is a hard problem, but maybe I am just missing pointers to the right literature.
2. CAD applications or Computer Games have lot's of triangulated objects. Their topology seems to be not to be very interesting. Again: In dimension <=3 there is really not that much going on. And since you have constructed the object yourself, you probably know the geometry already.
3. Graphs appear everywhere, and can be viewed as 1-dimensional chain complexes but do not have interesting co-homology groups.
4. Did anyone compute homology groups for "Manifold Learning"?
It's also not clear to me, how much interesting information can be extracted from those homology groups. Applications of Homotopy/Homology in (semi-classical) Physics are already quite slim (apart from Quantum Field Theory, String Theory, Gauge Theory?!) as most of it takes place in contractible spaces $IR^n$.
E.g. creating a company with a business model which benefits from taxing CO2 emissions (Tesla) is morally great. Whereas having a business model which benefits from cheap oil (VW) is less so. Product decisions (electric vs. fuel engines) have a large effect on your long-term financial interests.
Learned about REGEXEXTRACT and parametrized Strings.
Powerfull stuff.
As my job involves more and more Google Sheets Engineering lately. I really appreciate this kind of hacks!
AFAIK, this is the "micropayment" problem, that people were hoping bitcoin would solve.
This is very disrespectful to the many women, and a growing number of men that are making a conscious choice to prioritize raising children and caring for a family over salary work.
The problem is forced labor here, i.e. not having a choice to enter the work force. Not that the work is inherently "crappy" - it is not.
This is also the reason why notation is often terse, and highly domain/author specific. You get tired of writing long_variable_names very quickly if you do it OVER AND OVER by hand. Now think about how much work and confusion it would be to replace those symbols with little paintings...
https://www.amazon.com/Algebraic-Geometry-Projective-Varieti...
This get's very tedious to write if you use this over and over in proofs.
It's easy to forget, that if you are running "Python" in production, you are actually running CPython on a x86 VM configured with a bunch of *.py files. When things go sideways, you might find yourself in a situation where knowing CPython internals becomes relevant.
If you are re-architecting a system from the ground-up there is always some fallout expected.
What are the next steps for the community?
- Should we re-locate to a different space?
- Shall we wait until a lawsuit has been filed?
- Shall we wait until we have a legal response?
The good thing is that the website https://yt-dl.org is sill up, and the original author seems to have control over it. If there is some coordination behind it, I don't see why the community could not re-locate to a different place, where it is less likely to be sabotaged by what seems to be an inappropriate DMCA takedown.
My singing teacher started out as a voice therapist. He is still working with a lot of people with damaged voices that are there for therapeutic reasons as well as professional opera singers that there to level-up their game.
He says, the best thing you can do for your voice is to sing.
Singing will give you the proper "support" from your lungs and train the vocal muscles without wearing them out. One of the key aspects here is producing high quality vowels, and don't let the sound be disturbed by consonants. This is opposite to how the voice is used when speaking (in most languages), where consonants are of primary importance for people to understand what you are saying. However, consonants are interruptions in the air-flow and can easily wear the voice out and cause stain.
Why would you not look into the fake implementations? If it's just a two liner that takes the parameters and writes them to disk, then that's a LGTM from me. You would not test every getter/setter method in any of your classes, would you?
If it's more complex than this, you can absolutely write tests for your fakes. In many cases fake data-stores use tested backends, and tested client libraries. If the client wrapper is complex enough then you can/should test it as well.
Let X be a set, and
Fun(X) = { real valued functions on X }.
Indeed, if $F: X -> Y$ is a map between set, and f \in Fun(Y). Then you have a natural function $f \circ F: X -> IR \in Fun(X)$. This is sometimes called a pull-back of $f$.
Functors of the kind Space -> { some stuff* that lives on X } are often contra-variant. E.g. functions, vector bundles, sheaves, differential forms, etc.
I second this. From my experience you have to START WITH ACCEPTING the status quo and honestly looking at it without judging or being ashamed. It helps me to tell myself: "This is not terrible. I am alive. I have a job. My body is still working OK."
From there FOCUS ON THE DELTA: What can I do today that will bring me into a slightly better position tomorrow.
Avoid thinking about the past ("I ate too much today.", "I did not exercise all week."). This is done. No way to change it.
Don't set high expectations. You only need to know where you want to be, and that you are going into the right direction. It does not matter much if you arrive there in one week or in five years.
Unwrapping the last term alone is a multi-year endevour if you start from scratch:
> [A] manifold is a locally ringed space, whose structure sheaf is locally isomorphic to the sheaf of continuous (or differentiable, or complex-analytic, etc.) functions on Euclidean space [IR^n]. -- https://en.wikipedia.org/wiki/Manifold#Mathematical_definiti...
Note that definition, does barely use inventor's names and is still very dense and hard to unwrap.
I never found naming conventions to be a notable problem.
Topics:
* Best practices for C function signatures (caller allocates (which size?), callee allocates (where? which allocator?))
* Memory Ownership Models
* Borrowing
* Reference Counting
* Garbage Collectors and C-Libraries providing this functionality
* Interning Objects (Strings)
* RAII [1]? And it's benefits/flaws
[1] https://en.wikipedia.org/wiki/Resource_acquisition_is_initia...
Context: I feel that understanding the C memory primitives in not that hard (stack variables, malloc/free, C++'s new). But how to use them is devilishly tricky. I have seen little information about this.
As people pointed out here, hijacking Twitter accounts can lead to big stock market crashes, mass panics ("bomb found at XXX") and maybe even military escalations.
Under this circumstances, leaving a platform with an unknown number of compromised accounts online, seems irresponsible to me. In such a case you must stop the bleeding ASAP, either by locking up "important" accounts (what they eventually did, after a few hours!) or taking the site offline.
Next time this happens, we might not be so lucky.
I have tried to do it a few times, and eventually just gave up. Carrying forward bad naming decisions from the past, is tremendous effort. When cleaning up the house, I also don't leave around sticky notes at the places where I removed documents from.
On top of this:
- When using static site generators, it's not even possible to do 301 redirects (you would have to ugly slow JS version).
- It does not help if you don't own the old DNS name anymore.
http://www.pathfinder.com/money/moneydaily/1998/981212.moneyonline.html
0. Access protocol
1. Hostname/DNS name
2. Arbitrary chosen path hirarchy
3. File extension
This is really a description where to find a document ("locator" not "identifier"). So, if you are:
- re-organizing / cleanup your file structure
- change or hide the file extension
- enable HTTPS
- migrating files to a different domain name
This WILL change the URL. What are you going to do? Not cleanup your space anymore? Stick to HTTP? So URLs DO change. That's just the reality.
If you want something that does not change, don't link to a location but link to content directly: E.g.
- git hashes do not change
- torrent/magnet Links don't change
- IPSFS links do not change.
Or use a central authority, that stewards the identifier:
- DOI numbers don't change
- ISBN numbers don't change
X ~ s + eps
p(x_1,\dots,x_n) = C * exp(-(s-x_1)^2) * exp(-(s-x_2)^2) ... * exp(-(s-x_n)^2)
Log(p(x_1,\dots,x_n)) = - C' * sum_i (s-x_i)^2
This means if you set s to mean(x_i), you will maximize the "log-likelyhood" of your observation.
help() { cat $0 }
Professional wood-shop costs easily >$100K :)
Number one cost factor, IMHO, is space for a shop. You need enough room to store and handle lumber. If you have that, you can start with hand tools (saws, chisels, planes) for let's say ~300$. This will in-principle allow you to do everything. People have done this for ages, this way.
Power tools make woodworking much faster. I would start with a jig saw, drill press, circular hand saw. This will be another ~800.
The first expensive mile stone is the table-saw. This will be the most used tool in your shop. Everything gets better when you have access to a good table saw. I have spent 1.2K on mine.
Next upgrades are miter-saw, band saw, planer, jointer. They need a lot of space and are not cheap. This is were you enter the more professional realm.
To get high quality versions of all that tools will cost a lot of money. Oftentimes ebay has used tools for small money. E.g. I bought 15 hand planes for ~100 EUR last year and 50EUR for a used drill press.
Happy woodworking!
Makes browsing documentation really fast and convenient. Have that bound to F1 in my emacs to lookup the current word at point. So you instantly zap to man pages, lua reference manual, python docs, perl docs, ... you name it. Highly recommended.
echo '' | fzf --print-query --preview "cat *.json | jq {q}"