Month: March 2019

March 20 2019, 09:52

It’s truly a major revolution, comparable to iTunes in its time. Even if not everything is as perfect as claimed, the idea is fiery, with all the technical implementation in place. I’m not a gamer at all, but at first glance, there have been no conceptual changes for about twenty years after internet multiplayer.

https://meduza.io/shapito/2019/03/20/google-pokazala-igrovoy-strimingovyy-servis-stadia-emu-ne-nuzhny-konsoli-i-moschnye-kompyutery-tolko-brauzer-i-internet

March 17 2019, 14:38

This weekend, I got hooked on videos and podcasts about better understanding music and paintings. Regarding music – I highly recommend the Arzamas podcast https://arzamas.academy/radio/announcements/classical-music. It requires a subscription, but I haven’t regretted a single minute. True, I’ve nearly listened to everything they have; I accidentally subscribed for a year instead of a month – be sure to read the labels on buttons carefully)

About paintings: A fresh ‘masterwatch’ by Nerdwriter about “the most terrible masterpiece by Van Gogh” – the expressionist painting “Night in café”. When you start to look closely at the combination of colors and objects in it, you realize how powerfully the artist has conveyed a creepy and depressive state, and Nerdwriter (as always) skillfully explains the mechanisms of how this painting impacts the viewer. Even if you’re not at all familiar with painting, watching such videos is a pure pleasure: youtu.be/nKNAZr0QJzs

I also suggest a few more Nerdwriter videos decoding great paintings:

t.me/mustwatch/120 (“The Death of Socrates” – a classic story, a classic painting by Jacques-Louis David, and a deep analysis of how to properly perceive it)

youtu.be/WKRKrpz09Fk (“The Family of Philip IV” by Velázquez – a painting many consider the greatest in history due to its numerous meanings and references embedded in a simple family portrait)

youtu.be/7j5pUtRcNX4 (“Nighthawks” by Hopper – one of the most influential American paintings in history, grim and depressive)

youtu.be/Iu2L7oA9QRg (what does the cigarette on the self-portrait by Edvard Munch, better known for his “The Scream”, mean?)

youtu.be/_HGW1DQO1xQ (how to understand Picasso’s paintings)

youtu.be/5E8f64yj1Jk (why “The Night Watch” is the greatest masterpiece by Rembrandt)

youtu.be/g15-lvmIrcg (the most horrifying painting by Francisco Goya)

youtu.be/z68CQkD7mz4 (the subtle features of “The Bathers” by Cezanne, and why Picasso said “Cezanne is a father to us all”)

http://youtu.be/z68CQkD7mz4

March 14 2019, 18:18

Fellow programmers, remind me how to transform the list

a=(3,4,5,8,10), b=(1,3,8,10), c=(4,10), d=(8,10)

into

a=(e,4,5), b=(1,e), c=(4,10), d=(8,10), e=(3,d)?

Actually, for this purpose:

https://github.com/raliev/rulegroupspoc/blob/master/sampleoutput.txt

There is a matrix of 1 million users by 100,000 products and a set of rules dictating which product is available to which user. I have already developed a fast algorithm (still unoptimized) that creates a Products x Usergroups matrix, and calculates user groups. Under certain conditions, there will be significantly fewer user groups than products, and each product could be associated with a list of user groups, instead of a list of users. However, in the calculated groups, there are repetitions that could further reduce the list of groups to be stored alongside the products. This is where substituting “e” from the example above comes into play. But how to do this efficiently? Assume that there are 100,000 users, less than 50,000 groups.

March 11 2019, 01:42

In the photo is the NASA OV1-8 PASCOMSAT satellite, 1966. This one specifically is inflatable, but engineers, let’s fantasize – what if you were tasked with creating a hollow sphere covered with regular polyhedra, how would you approach the task? Assume it needs to be assembled from pentagons and hexagons. Then, to manufacture pentagons and hexagons separately, one must calculate how many are needed including duplicates, compute the convex and concave features, devise a method for reliable connections, and organize molds for casting. And this is just to manufacture the sphere.

I know the answers to the questions above, just an interesting educational problem for interviews and to assess people’s thinking abilities) And the photo at NASA turned out a bit crooked).

Okay, simple question – how many pentagons are needed to cover a sphere with pentagons and hexagons? The calculation fits into one Facebook comment)

UPDATE: In short, the correct answer is 12. Grigory Bakunov did well) There is a beautiful theorem by Euler, stating that for any convex polyhedron, the number of vertices minus the number of edges plus the number of faces will always equal two. If our polyhedron consists of X hexagons and Y pentagons, then the number of faces will be X+Y, the number of vertices will be (6X+5Y)/3, and the number of edges – (6X+5Y)/2. Here, 5 and 6 represent the number of edges of a pentagon and a hexagon, respectively, and the denominator accounts for the fact that two edges of a flat figure form one edge of a volumetric one, and the same thing for vertices, only with a three. So now, plugging this into Euler’s formula, we find that X drops out of it completely, and Y=12. This means that to tile a sphere with pentagons and hexagons, exactly 12 pentagons are needed, while the number of hexagons can be as many as necessary. Furthermore, to apply this pattern onto a sphere, the flat faces need to be projected onto the spherical surface, where they will simply transform into an arc. To assemble the sphere, you will need 12 pentagons (all identical) and some number of hexagons. Their number depends on the size of the pentagons. This too can be calculated, but it would be rather lengthy.

March 09 2019, 17:14

Somehow, I ended up reading the December issue of “Red Star”, just out of curiosity. People there speak in some strange language.

For example, in an article on the link, a guy is asked a rather specific question, “What should be our, or rather, your – Strategic Rocket Forces’ – response to the US deploying their missile defense systems in Eastern European countries?”. The response, when translated from this incomprehensible language into Russian:

“A number of measures have been developed to reduce the effectiveness of the USA and to accomplish the set objectives. These measures involve the creation of missile complexes. It is planned to develop scientific and technical groundwork and continue the efforts to create means of attack for the developing missile defense system” (I’m not lying, that’s exactly how it was written: “continue the work on creating means of fire and functional destruction of reconnaissance, control, and strike means of the developing missile defense system.”)

The printed version of the article contains two more paragraphs about nothing. Mentioning that inspections showed a high level of preparedness and everyone did a great job.

Let’s take another specific question. Journalist: (simplifying the question) In 2016 you mentioned that UAV models were not autonomous but controlled, which is bad. Is anything being done?

Answer: “Indeed, it required additional research. The research is being conducted successfully. The approval of the research results showed that most of it will be completed by next year.”

And so it goes there!

http://redstar.ru/nash-yadernyj-shhit-ostayotsya-nadyozhnym/