Volodymyr Obrizan: personal website - 29

Technical Blogs

2016-01-29T23:59:00+02:00

While you’re over there liking whatever random crap on Facebook (Facebook as a news outlet is just some kind of misunderstanding altogether), the normal guys are reading technical blogs from leading companies.

For example.

The Uber engineers’ blog: https://eng.uber.com/ Don’t know what Uber is? How are things back in the 1990s? Is Valdis Pelsh still speaking with an Estonian accent? For example, there’s an interesting article about how Uber’s engineers ran up against PostgreSQL performance and wrote their own NoSQL database based on MySQL, and the most interesting part — how they migrated a live system without a single minute of downtime.

Amazon’s cloud: https://aws.amazon.com/ru/blogs/aws/ For example, what Amazon did to survive the blizzard in the U.S.: https://aws.amazon.com/ru/blogs/aws/aws-ready-to-weather-the-storm/

Twitter: https://blog.twitter.com/ For example, how Twitter is migrating from the SHA-1 algorithm to SHA-256 in order to be a secure social network: https://blog.twitter.com/2015/sunsetting-sha-1

Facebook engineers on the line: https://code.facebook.com/ For example, how Facebook is advancing its hardware platform for efficient data centers, and even publishing all its inventions as open source: https://code.facebook.com/posts/1650070168592965/telecom-industry-embraces-open-compute-project/

Netflix: http://techblog.netflix.com/ For example, how they run automated fault-tolerance tests: http://techblog.netflix.com/2016/01/automated-failure-testing.html

While someone is holding forth on the advantages of one technology or another, these guys are deploying technologies for billions of users and know about it all firsthand.

I recommend subscribing and reading them cover to cover.

Couldn’t Make It Interesting

2014-11-29T02:17:00+02:00

I suggest readers take a look at this thesis from a student at KhNURE: “the problem of students not studying a subject -comes from the teacher. Couldn’t make it interesting.” (the author’s spelling and punctuation have been preserved).

Link to the source: https://www.facebook.com/evgen.sakalo.9/posts/945303185498928

The greatest tragedy of our world is that it has been turned upside down. We live in an upside-down world. Here everything is the other way around. The active has become passive. Regression has become forward movement. The cheap is valued more than the expensive. The faster you run toward a goal, the farther away from it you end up.

In the upside-down world, it wasn’t the applicant who wrote an application to be admitted to the university. In fact, he didn’t want to; it wasn’t his initiative — rather, the university staff attacked him and dragged him into the admissions office, where, under pressure from Evil Adults, he put down his signature.

In the upside-down world, it isn’t the student who takes an interest in the subject. It’s the teacher who has to make the student interested in studying his subject. In the upside-down world, nature did not instill curiosity in man; it removed it.

In the upside-down world, it isn’t the student who reads a book. It’s the book that has to interest the student — or better yet, jump into his head by itself.

In the upside-down world, the student is completely passive. It isn’t the student who decides what interests him. There are plenty of things besides education fighting for the student’s interest: computer games, movies, cartoons, TV series, nightclubs, parties, alcohol, drugs. Education is at an obvious disadvantage here because of the instant high everything else provides. And education does not give instant results, because everything genuine is hard, slow, demands all of you, is painful, but that is precisely what makes it valuable — the amount of energy and time invested. And an instant high is free and on every corner. You can’t learn C++ in 21 days. You can learn it in ten years.

Come to the lecture. Turn off the Wi-Fi, turn off your phone. Move away from your degenerate friends. Look at the board, listen to what the teacher is saying. Open your notes, write down the most important things. And repeat this again and again. Come to the lecture. Turn off your phone. Listen to the teacher. And again, again. Come to the lecture, write down the most important things. And repeat. And maybe, if you’re lucky (since you were unlucky from birth, unlike others in whom nature instilled a living interest in everything around them), by the end of the tenth lecture you’ll find it interesting.

If anyone has forgotten the meaning of the word, I’ll remind you.

Student — from Lat. studens — one who works diligently, studies.

One who works diligently. Studies.

You were walking along and spilled the meaning on the way. You are empty. You can call yourself Batman, but that doesn’t make you Batman. You can call yourself a student, but that doesn’t make you a student.

Assessing the Work of Higher Education

2014-03-29T15:05:00+02:00

Ukrainian scholars report:

According to the results of a survey conducted in October 2013, 30% of the Ukrainians surveyed consider the quality of higher education to be low or very low. According to the survey, 45% consider the quality of higher education average, and 15% consider it rather high or very high.

ZN.UA. A third of Ukrainians do not believe in the quality of higher education.

I conducted a survey among my acquaintances on the social network “Vkontakte” and got a similar result:

Any government of independent Ukraine — democratic (Kuchma, Yanukovych), nationalist (Kravchuk, Yushchenko) — has always been united in destroying higher education. Economic methods were used for this: cutting spending on education and science, laughable salaries for faculty.

Society did not stay on the sidelines of this process. Social methods were added to the economic methods of destruction: universities came to be seen as a place where you can “dodge the army,” “get a piece of paper so you can get hired,” while the formerly honorable job of teacher is now considered the lot of losers.

Business also wouldn’t mind taking a kick at the education system: here one can recall my note about how McDonald’s assessed higher education.

But I’ll tell you some good news and a big secret. The good news is that there are still students who make their way through thorns to the stars, keep studying conscientiously, and squeeze the most out of the situation as it is.

And the big secret is that the statistics above are a mirror that quite accurately reflects the number of sharp students. 10–15% of students in a group are sharp kids. 40–50% are average. The remaining 30–40% are made up of skippers, D-and-C students, or just dumbasses. Thus, it is very easy to find out a person’s level of preparation simply by asking how they feel about the quality of the knowledge they received.

Calendar for December 2012

2011-12-29T18:37:00+02:00

Funny how their calendar shows December 2012.

Could it really be the end?

By Reader Request

2011-10-29T23:33:00+03:00

Reader Maxim asked me to write some notes about the usability of the user interface in Eclipse.

Dear Maxim!

I haven’t yet managed to take advantage of all the benefits of the integrated development environment “Eclipse,” version 3.7.1, item M20110909-1335, because for two hours straight now I haven’t been able to install the Google AppEngine Toolkit into it. Nevertheless, already while installing extensions I started noticing interesting features of the user interface.

The figure below shows the progress window for installing an extension in the Eclipse 3.7 IDE. We see a progress bar, we see a description of the current operation. The following commands are available to us: perform the installation in the background, cancel the installation, show detailed information.

A classic of the genre: any installation process immediately jumps to 50% at launch, hangs in that state for an infinitely long time, and then instantly jumps to 100%. Thus, in this case the progress bar completely loses all the meaning that was built into it.

Hoping to find an indicator showing the time remaining until completion, the user may click the “Details” button. But disappointment will be waiting for him there.

Here we see the very same progress indicator and a description of the command being executed. One can also note the phrase “Installing Software,” which is mentioned as many as four times in such a small window. The “Details” button also does not perform the function implied by its name. There is no new information for the user here. It is hard to imagine a programmer so detached from the object of his labor that he could program such nonsense. But as shown above, on the Eclipse development team there is at least one.

In my view, the reason for this sort of degeneration is as follows: there is still too little quality software in our world. Since early childhood we have been using bad software. And many erroneous patterns have already been embedded deep in our consciousness. In the example, such an erroneous pattern is the presence of the “Details” button. But if there is nothing more to show, maybe this button isn’t needed? Even if there is nothing more to show, the programmer still makes this button, without realizing it, because he has been used to this button since childhood. Or think, for example, about what the symbols << and >> on this button mean. We will never know, because the person who first began using them has long since left us.

A few more examples can be given. Any program, even the simplest one, must have options (Options, Settings). But must it have them? Any program must have a menu with the mandatory sections File, Edit, Window, Help. But is that menu needed? Every program must have a toolbar. But must it have one? And so on.

To clarify add detail. Edward Tufte

Working with Sources

2010-11-29T16:54:00+02:00

“If I have seen further than others, it is because I stood on the shoulders of giants” Isaac Newton

After the research topic for an article (see “On Choosing a Topic for a Research Paper”) or for a term paper, thesis, or dissertation has been defined, you need to work very closely with the sources.

By a source I mean: a blog post, a page on a website, a research article in a journal or collection, already defended term papers, theses, dissertations, monographs, books, public talks.

Why do you need to do this?

In any case, by reading the literature you’ll get smarter and learn something. It’s unlikely you’ve undertaken to write on some topic you know inside and out. Well, let’s not kid ourselves: even when working on something well known, you have to peek into handbooks and other sources to double-check facts or quote something.
In most formats (article, term paper, thesis, dissertation), a literature review section is mandatory. Usually this list is checked so that there are no “Murzilkas” in it (sources that have nothing to do with the topic of the work). A simple piece of work like a term paper should rely on 5–10 sources. For dissertations, that bar is raised to 100–200 sources.
Studying the literature will keep you from ending up in a stupid situation where your seemingly unique and brilliant idea was already described in detail by someone about twenty years ago. Studying the literature lets you confirm scientific novelty.

Show some respect for your academic advisor and the scientific community. Use your capacity for self-education before asking questions or publishing your results.

Before you start working with sources, you need to find them. You should start searching with general formulations. For example, if you’re writing about hardware synthesis, that’s exactly the query you make: “hardware synthesis.” As you go deeper, the wording will become more complex, for example: “a method for interface synthesis from C++ description.”

Where should you start searching? The easiest way, of course, is to do it sitting at home in front of the computer. Libraries and search engines for (mostly) English-language articles:

IEEE Computer Society Digital Library (paid) — periodicals and archives of conferences held under the umbrella of the IEEE Computer Society. There are several dozen publications and several hundred conferences. Student (graduate student) membership in IEEE, Computer Society, and access to the digital library may together cost around $100 a year. But when conducting research, that money will save you time searching for the articles you need.
ACM Digital Library (paid) — periodicals and archives of conferences held under the umbrella of ACM. Registration + library access will also cost around $100.
CiteSeer (free) — in fact, this is not a library, but a kind of “Google” for articles. The search crawler scans the internet for freely available article texts. It remembers the title, authors, and links to other articles. The PDF file itself is cached on the server.
Google Scholar (free) — also a search engine; it scans many sources (including the ones mentioned) and shows both paid collections and free ones.
arxiv.org (free) — yet another search engine for articles.
Various publishers that provide free access to their periodicals, for example, http://www.hindawi.com/journals/

Unfortunately, I don’t know of any decent Russian-language search engines or collections. I’d be grateful if blog readers pointed them out in the comments.

Don’t neglect ordinary libraries. At one point I tried to find, on the internets, a book published in the USSR in the 70s. The search led me to just one person, who was willing to sell it and ship it from Peter. Then a mega-genius thought occurred to me: go to the university library. The habit of searching for everything on the internet without lifting my torso from the chair played a cruel joke on me. I found the book I needed (and several more interesting ones) in 10 minutes in the catalog room, and it took another five minutes to order those books from storage. 15 minutes, and I had the necessary books in my hands, which helped me make my dissertation better. The drawback of an ordinary library is that it has few English-language publications, as well as few recent publications from the last few years.

All the articles you obtain need to be organized on the computer in some uniform way. The bibliographic reference should be entered into a special Word file. Articles can be put into separate little folders by topic or by author.

And if that little folder is also indexed, it will be much more convenient. Sooner or later, a lot of documents will pile up, and keyword search will be very handy.

It may happen that a simple internet search will turn up an insufficient number of articles. That’s no problem at all. Now we’ll just use another search method.

1. Searching by references

Because it is considered necessary to cite other sources, all articles are in the kind of relationship shown in the figure:

Here the red article is the article you found, for example, through Google. Usually at the end of every article there is a section called “References” or “Sources.” In this example, the red article cites one gray and one green article. If the author of the red one cited them, there is a very high probability that those articles are also related to the research topic. Which means you must definitely find those articles, study them, and then incorporate them into your work. Pay attention to the green article. It is old, and it has as many as three citations. It is probably some foundational work that describes the basics or first defines one problem or another. Most likely you won’t find the solution to your specific problem in it, but it may prove quite useful for understanding the overall picture and the history of the issue. This is what a typical references section looks like:

Be sure to find those little squares with numbers in the text of the article. Then you’ll be able to understand where the author cited the source. This will help you understand the context.

Things are a little more difficult with the blue articles. These are the articles that cite the red one. The problem is that at the time of publication, the author cannot know who will cite this article in the future. But usually sites with article archives build these lists themselves during indexing. If you see that someone has cited an article on the topic you’re interested in, you can safely take a look at that work. It is quite likely that it proposes a new solution or a development of the idea. You can also find out who cited the current article through Google. Just copy the article title and paste it into the search engine in quotation marks.

2. Searching by author

You found an article and it seemed interesting to you. Look at who the author of this article is. Usually, over the course of a year or several years, an author publishes several articles in which they consistently develop one topic or several related topics.

By entering the author’s full name in Google, you can find his home page, where all his works from recent years will be listed. And there may also be direct links there to PDF files with the text. Great success! Again, besides Google, sites with article archives that can filter by author will help you.

3. Searching by collection or journal

You should also pay attention to the publication (periodical journal or collection of articles) in which a given article was found. It is quite logical that all conferences have a single theme. Therefore, by googling (or filtering on the article site) by the conference name, you can find articles similar to the one you have already found by other means. And if you stumble onto the archive of some conference on your topic — then that’s easy street!

And in conclusion I want to remind you about Lenin’s curve (learning curve).

Sooner or later, after reading the 100th article on the topic, you will realize that you are no longer learning practically anything new. And finding an article that contains something fundamentally new or important will already become rather difficult. That means you’ve already saturated yourself with knowledge on this topic. And surely you can already go out there and confidently hold forth against venerable professors in a scientific dispute. It’s time to stop searching and finally sit down to write the term paper, thesis, or dissertation.

Yes, and let’s not be lazy. We still have to raise domestic science from its knees after the democrats, together with the effective managers, made such a mess of things.

See also

Hobbies

2010-09-29T22:36:00+03:00

When I was a kid, I had several hobbies. My brother and I collected empty cigarette packs. But then we threw them out. Then we collected tin cans: from beer, vodka, and soft drinks. We gathered more than 160 of them (different ones). They gathered dust, ruined the interior, and we threw them out.

In 2002 I decided to start another hobby. It has to do with postcards and travel. Before 2002 I rarely traveled. Well, I went to the seaside a couple of times. And sometimes to the suburbs for the summer. But in the summer of 2002 I went to Poland for an internship. That’s when it all started.

I really like Jules Verne’s novel Around the World in 80 Days. The main character—Willy Fogg—had to check in at British consulates in the cities he visited, to confirm the fact of his movement along the round-the-world route. I wanted to do something similar.

The rules are very simple. I need to come to some city. Buy stamps and a postcard with a picture of that city. On the back, write under what circumstances I ended up in this city (for example, a conference or vacation), and possibly also mention who I’m at the post office with right now, what the weather is like. Then put down my home address and drop the postcard in a mailbox.

In total, my collection has 34 postcards (including repeats) from 21 cities in 5 countries. Not once has a postcard been lost or failed to arrive.

Poland: Katowice, Krakow, Gdańsk, Przemyśl, the Tatras, Sopot, Gdynia, Gliwice, Warsaw.

Ukraine: Dnipropetrovsk, Kyiv, Lviv, Odesa, Luhansk, Yevpatoria.

Russia: Moscow, Saint Petersburg, Nizhny Novgorod, Sochi.

Latvia: Riga.

Armenia: Yerevan.

I was in Poltava, but unfortunately, at all the post offices I managed to visit, they only had postcards saying “Happy 75th Anniversary!” and “Happy Diamond Wedding Anniversary.”

At the main post office in Odesa they stamped it and canceled the stamps on the picture side. On the back, the lady from the post office had to cancel the stamps with just a ballpoint pen.

In Luhansk I didn’t find any postal postcards, but I did find ordinary ones (the kind sold in a pack). There were no mailing fields on the back, but I found a free spot, wrote the address, stuck on the stamps, and dropped it in a mailbox. The postcard arrived. That’s when I realized that any piece of cardboard with an address and stamps will get there.

In Warsaw I had very little time (a few hours between transfers), and I didn’t find a post office. So in broken Polish I asked the saleswoman at a kiosk to stick on some stamps and drop the postcard in a mailbox in her free time. And she stuck them on and dropped it. So the Warsaw postcard can be considered a cheater one. That was in 2004; since then I don’t do that anymore. If I couldn’t find a post office, it means I didn’t deserve a postcard. Some of my friends know what a bore I am when traveling. When everyone goes to the beach, I turn around and go downtown to look for a post office. I’ve noticed that postcards can be sold anywhere, but stamps—only at the post office.

Recently I found out that Lebedev also collects postcards (see from 2:10). My collection, of course, pales in comparison with Tyoma’s. He has been to a hundred countries and several hundred cities. But your own collection is your own collection. I’m not planning to stop yet.

It so happened that my collection split in two. Knowing about my hobby, friends simply started sending me postcards. My friends travel more than I do, so the “other people’s” collection has all sorts of cities I haven’t been to yet. So if you’re going to the South Pole, give me a shout, I’ll scribble down my address for you. :)

And what stupid hobbies do you have?

IBM Grants for PhD Students

2009-09-29T14:09:00+03:00

IBM has announced the start of the competition under the “IBM Ph. D. Fellowship Awards Program. IBM Grants for PhD Students” for the 2010–2011 academic year. The “IBM Ph. D. Fellowship Award” program is an annual international competition that encourages talented PhD students conducting research in areas that are key for IBM and form the foundation for innovation.

IBM Ph. D. Fellowships are awarded only to full-time PhD students nominated by their academic advisers.

Application period for participation: from September 22 to October 29, 2009.

https://www.ibm.com/developerworks/university/phdfellowship/

Cinder Blocks of Parallel Programming

2009-05-29T22:06:00+03:00

There are several ways to get programmers to solve assigned tasks at high speed with a minimal number of errors.

The first way is to use high-level languages, for example, C++. Object-oriented programming makes it possible to create entities of various kinds in code, as well as define operations on them. As a result, we get at our disposal a set of certain objects that correspond to objects from the problem domain of the task being solved, with high-level properties and methods. Implementation details are hidden behind these high-level methods, which allows the programmer to focus on solving the task.

The second way is to use modern tools: compilers, test generators, formal verifiers, profilers. Compilers use internal optimizations to obtain better time characteristics and minimal memory costs. Examples of such optimizations include automatic pipelining, unrolling (rolling up), or parallelization of loops, which produces a faster implementation of the program. In this case, the compiler handles the routine programming tasks, and, as is well known, it works much faster and makes mistakes less often than the programmer.

The third way is to use methodological support. Numerous design methods and so-called patterns have been developed — approaches to solving one task or another in a certain context. Numerous books and manuals have been published, devoted both to programming as such, to solving abstract tasks, and also to application in specific tasks of the national economy.

The fourth way is to use libraries that contain ready-made, tested solutions: algorithms and data structures. Using library components, first, reduces development time, and second, reduces project testing time, because library components have been tested in advance and have repeatedly been introduced into industrial projects. Thus, the amount of library code can substantially exceed the amount of code written by the programmer.

Let’s do a brief overview of technologies that increase the productivity of programmers developing parallel applications. For many years the most accessible way of multithreaded programming was to use the Windows API or POSIX Threads library. The programmer had to solve the assigned tasks at a very low level. For example, the programmer needs to:

create and delete threads on their own;
determine the functions that should be executed in a thread;
pass the needed parameters into the thread;
use various functions to synchronize threads;
ensure an even load of the threads with computations;
take care of the scalability of the resulting solution.

Obviously, the drawback of this approach is that converting a sequential program into a parallel one can take a lot of time. The resulting solution will also be prone to many errors.

Some of these problems were successfully solved in the OpenMP library. This library is implemented as a set of functions and directives — special extensions to the compiler. The programmer applies one directive or another in the required place, and the compiler inserts calls to system functions at the specified place. For example, parallelizing a loop is done with a single directive to the compiler. In doing so, the compiler will take care of creating and synchronizing threads, dividing iterations among threads, and also of good load balancing. This approach makes it possible to solve a limited class of tasks practically without errors and in a short time.

But the OpenMP library has a number of limitations and drawbacks. We will indicate only some of them.

Loops with an unknown number of iterations cannot be parallelized.
Substantial limitations on loop parameters.
Limited possibilities for distributing work among threads.
The reduction operation is limited to eight elementary operations.
No more complex templates than a parallel loop or a parallel section.

Intel Threading Building Blocks (hereafter TBB) is a new library for multithreaded programming, developed by Intel. The library has a number of functions and classes for solving common tasks in parallel programming:

the parallel_for function for organizing a parallel loop;
the parallel_reduce function for a parallel loop with subsequent combination of partial results;
the parallel_while class for creating a parallel loop with an unknown number of iterations;
the pipeline class for organizing pipeline computations;
containers with parallel access capability: concurrent_vector, concurrent_queue, concurrent_hash_map.

TBB introduces the concept of a task object — a C++ class in which operator () is defined, which performs the assigned task (see the listing below). Depending on the algorithm in which the task object is used, this operator, for example, may take as a parameter a range of iterations (parallel_for, parallel_reduce) or the next element for processing (parallel_while, pipeline).

`// Класс-задача class Body { public: // Оператор-обработчик void operator() () { // Здесь расположены вычисления } };

* This source code was highlighted with Source Code Highlighter.`

Here you can see the difference from programming ordinary threads: the programmer creates tasks, not threads. During initialization, the TBB library creates the necessary number of threads, and the built-in scheduler assigns tasks to these threads while the program is running.

The template functions parallel_for and parallel_reduce work with ranges (iteration spaces). The TBB library provides two classes for this: blocked_range and bloced_range2d, one-dimensional and multidimensional space, respectively. TBB recursively divides the original range into many blocks, which are passed as parameters to the handler operator. Thus, each task object performs computations over its own portion of iterations. Let us give an example of using a one-dimensional range.

<span style="font-family:Courier New;font-size:85%;color:black;">blocked_range<<span style="color:#0000ff;">int</span>>(begin, end, grainsize)</span>

Here the template parameter is the type of the range elements, begin is the starting point, end is the ending point. The pair begin and end describes a half-open interval [begin, end); for example, the loop for (int i = 2; i < 5; i++) corresponds to the interval [2; 5) and includes iterations 2, 3, 4. The grainsize parameter determines the size of an indivisible block of iterations. In the event that, at the next stage of dividing the original range, a block smaller than grainsize is encountered, it will be considered indivisible. The figure below shows an example of recursive division of the range blocked_range(0, 10, 3).

To conclude the article, let us give an example of parallelizing a for loop.

`#include "tbb/blocked_range.h"

include "tbb/parallel_for.h"

include "tbb/task_scheduler_init.h"

using namespace tbb;

///////////////////////////////////////////////////////////////////////////////

// Класс-задача class MyTask { public: // Метод-обработчик выполняет функцию Calculate для каждого элемента // блока итераций. void operator() (const blocked_range<int>& r) const { for (int i = r.begin(); i != r.end(); i++) Calculate(i); } };

///////////////////////////////////////////////////////////////////////////////

int main() { // Инициализация библиотеки ТББ task_scheduler_init init;

// Запуск шаблона parallel_for, который принимает два параметра: // * объект диапазона итераций [0, 1000000) // * объект-задачу parallel_for(blocked_range<int>(0, 1000000, 10000), MyTask);

return 0; }

///////////////////////////////////////////////////////////////////////////////

* This source code was highlighted with Source Code Highlighter.`

News from Domestic Education

2009-05-29T18:22:00+03:00

The quality of education at KhNURE was assessed by a delegation from Kuwait. After which a decision was made at that country’s government level not to send students to us for studies because of its low level.

Kuwait will not send specialists for postgraduate study at Ukrainian universities and is refusing to have students study at five Ukrainian higher education institutions. The corresponding recommendation by the country’s Ministry of Higher Education has already been approved by the government of Kuwait, writes Al-Qabas.

The publication provides a list of the universities that fell under the ban. Among them are: Sumy State University, the Ukrainian Medical Stomatological Academy of Poltava, Kharkiv National Medical University, the Ukrainian State Academy of Railway Transport in Kharkiv, and Kharkiv National University of Radio Electronics.*

http://life.pravda.com.ua/problem/4a1fec1ba9693/

I think I’ll give the fourth-year students an exam in parallel programming.