Image: TED Conference , CC BY-NC 2.0

In April 2017 published an article Will Gornalla from the University of British Columbia and Ilya Strebulaeva Stanford called "We bring venture business assessments to reality." In it, scientists analyzed the estimates of more than hundreds of world-famous companies (including technological ones) with an estimate of one billion dollars or more (the so-called "unicorns").

It turned out that these estimates do not always correspond to reality and can be repeatedly overstated. We publish the main findings of this study.
MeLavi 27 september 2017, 9:19

The order of evaluation of expressions is determined by a particular implementation, except when the language guarantees a certain order of calculations. If, in addition to the result, evaluating the expression causes changes in the runtime, then the expression is said to have side effects.
MSDN
In our internal newsletter about C #, a regular question arises, which concerns the correct interpretation of such constructions:

a -= a *= a;
p[x++] = ++x;
In response, I ask:
Yes, who writes such a code with an imperturbable look? It's one thing when you write this, trying to win at the International COC Contest, or if you want to write a puzzle - but in both cases you realize that you are doing something non-standard. That, there really is someone who writes a - = a * = a and p [x ++] = ++ x; and thinks to himself "Shit, yes I write really cool code! "
KlauS 26 september 2017, 9:31

[A Friday translation of the 1999 article by one of the authors of the Thief game engine, Sean Barrett]
Unpleasant situation in "Sapper"
In this situation, I know that there are a lot of mines around me, but I can not determine where they are. Several mines can be in one of two places (pink or blue), a group of mines can be located in one of two combinations (light / dark green). In addition, there is still a difficult situation with "5" and "6" in the upper left corner, which I did not single out.

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Blue / pink - mutually exclusive pair, light / dark green - mutually exclusive group
"Sapper": logic or probability
In "Sapper" you can play in two ways: as a logical or probabilistic game.

Technically, probability implies logic. If you can logically prove that the mine must be in a certain place, then the probability is 100%. If you can prove that it is not in this place, then the probability is 0%. That is, in a sense, only probabilities are important to us. However, the player uses logical deduction to recognize such 100% situations. Sometimes, especially at low levels of complexity, it is enough to pass a level, no calculation of probabilities is required.

But there are situations when the whole logic of the world can not save you. A simple example is the situation with the "T", which can be seen down the center. It is slightly complicated by additional neighboring mines. (In the simplest case, "2" is replaced by "1", and "5" - by "3", so that the situation is symmetrical.)
KlauS 25 september 2017, 7:07

For testing, the code should be selected and copied directly from tweets . - approx. trans.

I recently found this tweet from <a href="https://twitter.com/FakeUnicode/"> @FakeUnicode < / a>. There was a JavaScript snippet that looked pretty innocuous, but displayed a hidden message. It took me some time to understand what was going on. I think that the record of the steps of my investigation may be of some interest to someone.

Here is the snippet:

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What would you expect from him?

Here we use the for in loop, which passes through the enumerable properties of the object. Since only the property A is specified, we can assume that the message with the letter A will be shown. Well ... I was wrong. : D
KlauS 23 september 2017, 8:40

An amusing find was shared today by the user fj333 with Reddit . Analyzing Qualcomm Technologies' proprietary code for Android, which appeared one year ago, he found that an unknown programmer decided to use the sorting with a bubble in production-code in order to find ... maximum in the array.

You can view the original file by under the link to Github or under the cut, and any owner of the device with Qualcomm Snapdragon 200 MSM8610 running Android can estimate it in operation.

As anyone who is familiar with sorting algorithms knows, sorting by a bubble is an educational algorithm, and in industrial code it is usually not used due to its inefficiency ; The matter is that in the worst and average cases it has the complexity O (n2) , besides its capacitive complexity in this case - O (n) . Whom it was not convinced - to use the sorting by a bubble does not recommend even Barack Obama .

And this is all not taking into account the fact that to search for the maximum would be enough and a simple search.
v1d0q 22 september 2017, 14:54

The story of how NASA, ESA, the Danish Technological University, neural networks, decision trees and other good people helped me find the best free hectare in the Far East, as well as in Africa, South America and other "so-so" places.

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kleop 22 september 2017, 8:56

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In this series of articles, I'll talk about the internal Android device - about the boot process, about the contents of the file system, about Binder and Android Runtime, about what they consist of, how the applications are installed, running, interacting with each other, about the Android Framework, and on how Android provides security.
kleop 21 september 2017, 14:37

"I experimented with the tasks of the cubic representation in the style of the previous work of Andrew and Richard Guy. The numerical results were amazing ... "( comment on MathOverflow)
That's how the retired mathematician Allan MacLeod came across this equation several years ago. And it's really very interesting. Honestly, this is one of the best Diophantine equations I've ever seen, but I did not see very many of them.

I found it when it began to spread like a network-nesting picture-pseudomem, invented by someone's ruthless mind ( Sridhar , was it you?). I did not understand right away what it is. The picture looked like this:

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"95% of people will not solve this riddle. Can you find positive integer values? "

You probably already saw similar pictures-memes. It's always the cleanest rubbish, clickbites: "95% of MIT graduates will not decide it!". "She" is some stupid or poorly formulated task, or a trivial warm-up for the brain.

But this picture is completely different . This meme is a clever or malicious joke. Approximately 99.999995% of people have not the slightest chance to solve it, including a good part of mathematicians from leading universities that do not deal with the theory of numbers. Yes, it is solvable, but at the same time it is really complicated. (Incidentally, it was not invented by Sridhar, more precisely, not completely.) See the story in this comment ).

You might think that if nothing else helps, then you can just make the computer solve it. It is very simple to write a computer program to find solutions to this seemingly simple equation. Of course, the computer will find them sooner or later, if they exist. Big mistake . Here the method of simple computer enumeration will be useless.
xially 20 september 2017, 13:56

Providers of the Russian Federation, for the most part, use the systems of deep traffic analysis (DPI, Deep Packet Inspection) to block sites included in the register of banned. There is no single standard for DPI, there is a large number of implementations from different DPI providers that differ in the type of connection and type of work.

There are two common types of DPI connection: passive and active.
Passive DPI
Passive DPI-DPI connected to the provider network in parallel (not in the section) either through a passive optical splitter or using the mirroring of user traffic. This connection does not slow down the speed of the network provider in the case of insufficient DPI performance, which is why it is used by large providers. DPI with this type of connection can technically only detect an attempt to query for prohibited content, but not to suppress it. To circumvent this restriction and block access to the denied site, DPI sends a specially crafted HTTP packet to the user requesting the blocked URL, redirecting to the stub page of the provider, as if the requested resource itself had been sent by the user (the IP address of the sender and the TCP sequence are forged). Because the DPI is physically located closer to the user than the requested site, the forged response reaches the user's device faster than the real response from the site.
v1d0q 17 august 2017, 17:40

The Unreal Engine project continues to develop - new code is added, and previously written code is changed. The inevitable consequence of the development in a project? The emergence of new bugs in the code that a programmer wants to identify as early as possible. One of the ways to reduce the number of errors is the use of the static analyzer, 'PVS-Studio'. If you care about code quality, this article is for you.

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Although, we did it (https://www.unrealengine.com/blog/how-pvs-studio-team-improved-unreal-engines-code) two years ago, since that time we got more work to do regards code editing and improvement. It is always useful and interesting to look at the project code base after a two-year break. There are several reasons for this.

First, we were interested to look at false positives from the analyzer. This work helped us improve our tool as well, which would reduce the number of unnecessary messages. Fighting false positives is a constant task for any developer of code analyzers.

The codebase of Unreal Engine has significantly changed over the two years. Some fragments were added, some were removed, sometimes entire folders disappeared. That's why not all the parts of the code got sufficient attention, which means that there is some work for PVS-Studio.

The fact that the company uses static analysis tools shows the maturity of the project development cycle, and the care given to ensuring the reliability and safety of the code.

We won't be talking about all the errors that we found and fixed, We will highlight only those that deserve attention, to our mind.

Read more - https://www.unrealengine.com/en-US/blog/static-analysis-as-part-of-the-process

P.S. Those who are willing, may take a look at other errors in the pull request on Github. To access the source code, and a specified pull request, you must have access to the Unreal Engine repository on GitHub. To do this, you must have accounts on GitHub and EpicGames, which must be linked on the website unrealengine.com. After that, you need to accept the invitation to join the Epic Games community on GitHub.Instruction (https://www.unrealengine.com/ue4-on-github).
Kate Milovidova 27 june 2017, 12:50
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