KUKURUKU HUB

Qt 5.2, From a Sketch to Google Play

Written by xanm

Dear colleagues, I’ve been told about Qt 5.2 and its new feature of simple and quick creation of cross-platform applications for Android and iOS. I opened Qt website and watched a great video, in which Hello World application was developed for Android and iOS in 10 minutes. I was impressed. So I decided to take up mobile development. I had a plan of working my way up from a wish to develop an application to its publication in Google Play. At the same time I learnt about the famous Flappy Bird and that its developer had decided to delete his application. So I wanted to develop another copy of thus game. But my main goal, of course, was to try out new Qt facilities. C++ or Javascript? I like C++, but I didn’t dare to write such a small thing on it. C++ makes developer be very thoughtful and attentive

Multitasking Management in the Operating System Kernel

Written by LifeV

As tasks share time on one processor kernel, I had to deal with multitasking management. Or rather pseudo-multitasking as tasks share time at one processor kernel. At first I’ll try to tell about the types of multitasking (cooperative and preemptive). Then I’ll move on to scheduling principles for the preemptive multitasking. The article is optimized for first-readers who want to understand how multitasking operates at the kernel level. But as everything will be accompanied with examples which can be compiled and run, it may interest the ones who are familiar with the theory, but have never “tasted” the scheduler. Introduction To begin with, let’s define what “multitasking” means. Here’s the definition from the Wikipedia: In computing, multitasking is a method where multiple tasks, also known as processes, are performed during the same period of time. The tasks share common processing resources, such as a CPU and main memory. In the

Lock-free Data Structures. Basics: Atomicity and Atomic Primitives

Written by khizmax

Lock-free data structures are based on two things – atomic operations and methods of memory access regulation. In this article I will refer to atomicity and atomic primitives. To begin with, I would like to thank you for a warm welcome of Lock-free Data Structures. 1 — Introduction . I can see that lock-free topic is interesting and it makes me glad. I planned to build a series according to academic concept, flowing from basics to algorithms, at the same time illustrating the text with the code from libcds. But part of the readers wants me to show them, without any delays and rambling on, how to use the library. I agree that there is some reason in it. After all, it’s not interesting for me either to know what is inside the boost , — and how to apply it! So I will divide my epic series into three

Top 10 FinTech Startups

Written by Jane

Financial technology or simply Fintech is one of the prominent lines of business nowadays. Fintech projects mostly focus on providing software infrastructure for finance-related activities. There is a great number of new innovative projects that we all can benefit from and Fintech projects help those initiatives with finance-related issues. Today we would like to present top 10 Fintech Startups that deserver your attention. 1. SDK.Finance It is probably the most innovative and versatile Fintech company on this list. It is the back-end software for the quickest technological start of any FinTech products. The company has recently won the best Fintech startup of 2015 award hosted by Central European Startup Awards. Loyalty programs, Gift cards, E-wallets, Payment systems, Billing systems, Bitcoin based services, Mobile payments, P2P money transfer, Lending platforms and other finance products can be built with SDK.finance back-end software in the shortest terms. Companies usually spend about a

Go Learn Golang! Introduction for Beginners

Written by andrew

Hi, my name is Andrey Grehov and welcome to “Learn Go Programming Language From Scratch”. This series of articles is going to be a short course to get you comfortable programming Go. Go, also commonly referred to as golang , is a programming language developed at Google. It is a statically-typed language with syntax loosely derived from that of C. However, it is a new language across the board. In every respect the language was designed by thinking about what programmers do and how to make programming, at least the kind of programming we do, more effective, which means more fun. We’re going to go through all of the core features, focusing first on regular syntax, the essential task of creating variables and functions, basic program flow, and how these things are different here. Go rethinks the traditional Object Oriented development you might be used to while still providing

How to Share a Channel Between Slack Teams

Written by Alexander Lashkov

Odds are you’re in love with Slack. This new tool is a fantastic way to keep your team on the same page—and cut back on email. Unfortunately, Slack has a limitation: it doesn’t easily connect disparate (e.g. external and intra-company) teams. For example, in an agency, your team can use Slack to reduce call volume and expedite communication. But, what if the clients you work with have their own Slack, and don’t want to create new accounts? We’ve talked to a number of folks who find such situations a real bother. Admittedly, this is a notable shortcoming in an otherwise great platform. There are, however, a handful of ways to solve this problem. Curious? Read on: Option 1: Create a New Slack Team The most common way to bridge the gap between two teams is to create a new Slack team. This seems like a low-friction solution, and in

Client Communication is Killing Your Agency (And How to Fix This)

Written by Alexander Lashkov

Many are drawn to the idea of running a creative agency: interesting projects; great creative minds; and, of course, ideas people take notice of. Nevertheless, the challenges of agency life can prove a rude awakening, for the new agency operator. Keeping your agency profitable relies on many variables. You need even cashflow, dependable processes, and a little bit of luck. That said, the lifeblood of any creative company is communication. That’s what I’m going to cover today: how client communication impacts the bottom line—and the quality of life for all involved. (Oh, yeah, and I’m pitching my product, too—because someday it’ll save your ass.) Slo-mo to Crunch Mode As you probably already know, the underlying challenge for any agency lies in establishing a healthy balance. This requires you to juggle a number of ongoing projects and delivery times, while maintaining work quality. You’ll need to do this while managing

A Game in 14 Days

Written by Allex

NB: English is my second language. There is Russian language in videos and screenshots. There are a lot of “teams” that have existed for years. Their list of developers consists of dozens of people, plus, “everyone needed!”. But they don't have any adequate demo planned even for the nearest future. Looking at all of this, I feel like saying: “What are you doing, damn it?”. But it’s destructive. It’s not enough to criticize. I should provide positive examples. These considerations led me to an interesting experiment. I came across a flight simulator competition. It involved two months of development, but I thought that it was too much. That’s why I decided to take part in it. And… Forgot about the competition for a month and a half. The basic idea of the experiment is to develop a complete project within two weeks. The completion date of the competition is

The Night of Fractals

Written by Matvey Kotov

It was a late Sunday night, and I was thinking to go to sleep, when a friend of mine sent me a picture from some website and wrote: “Beautiful!”. I drew such pictures five years ago by using the so-called escape-time algorithm. But to apply this algorithm, it was necessary to know how to partition the plane into regions for a given set of transformations. I couldn't figure it out, and did not get back to this algorithm anymore. But now I knew exactly what should I do and wrote him back: “Random IFS first, then kNN, and then the Escape-Time Algorithm!” I had an old netbook at hand, as my laptop was under repair. My friend was saying something to me, and I was answering him, but in my mind I was already writing code, and was searching for at least some compiler on the netbook. And I

Do Not Wake the Programmer Up!

Written by Alex Hunder

Hey there! I’m back from the first vacation in my life… and I guess that some people have not been on vacation in their entire life. I’m not sure that it’s useful to take a break from work for almost a month. I haven’t realized what effect it would have on productivity. But during the holidays, I understood something about things I’ve been thinking about for a while, but couldn’t realize them. I was always tormented by the following question. How to explain to people who have never done the kind of work I do, the idea of what happens in my head and heads of others like me when we work? How a NON programmer can imagine a programmer’s work and finally understand what happens there and what to do about it? I think I understand it now. Maybe because I’ve been out of this process for almost

Quantum Search Using Grover’s Algorithm

Written by Roman V. Dushkin

Following the first quantum algorithms we have already reviewed ( Deutsch’s algorithm and the Deutsch-Jozsa algorithm — it's better to read these articles first, otherwise all the things mentioned here will be quite vague), let’s analyze Grover’s algorithm for the unstructured quantum search. An American mathematician Lov Grover formulated the algorithm in 1996 (it was long after the model of quantum computations had become popular). The algorithm uses a feature of quantum interference in order to solve an extremely demanding task of searching the value of some parameter, at which a defined function returns certain results. The given algorithm does not show the exponential advantage of the task in contrast to the classical computational model, but the advantage (quadratic) is quite essential for big values. However, it’s a general algorithm for solving quite a generalized problem. It has been proved that we cannot get a better result within the

A Short Course in Computer Graphics. How to Write a Simple OpenGL. Article 1 of 6

Written by Dmitry Sokolov

Describing the Task In this series of articles, I want to show the way OpenGL works by writing its clone (a much simplified one). Surprisingly enough, I often meet people who cannot overcome the initial hurdle of learning OpenGL / DirectX. Thus, I have prepared a short series of six lectures, after which my students show quite good renderers. So, the task is formulated as follows: Using no third-party libraries (especially graphic ones), get something like this picture: Warning you, that it is training material that will generally repeat the structure of the OpenGL library. It will be a software renderer. I do not want to show how to write applications for OpenGL . I want to show how OpenGL is built. I am deeply convinced that it is impossible to write efficient applications using 3D libraries without understanding this. I will try to make the final code not

Hacked. A Short Story.

Written by kay

It all started when I was asked (as a freelancer) to configure exim4 , so that newsletters would not fall into spam folders. They even sent me a link to a tutorial. I thought the work would take a couple of hours, including the DNS update, but I was wrong. After logging in as root , I started my favorite screen by running the  screen -x command as usual, and watched a curious scene in the favorite for many of you /dev/shm folder. The attacker either did not bother to close the screen session, or was still working in it. That’s where the quest begins: The first thing I did was looking at the things the attacker was doing: wget http://ravenul.zzl.org/it/noi/up/8.txt mv 8.txt list.txt php lol.php php lol.php netstat -an | grep :22 w rm -rf list.txt w rm -rf .x netstat -an | grep :22 Apparently, he sent

Singularity of the Humanities

Written by 2252

Our individual perceptions as well as the collective societal-perceptions are rarely in synch to enable us to love another or to serve one another as we are challenged to do. Over the centuries the humanity and the humanities have struggled to cope with this challenge. While this challenge might seem unsurmountable, it need not remain so for ever. Just as our visual acuity is improvable with the help of the prescription lenses; humanities can achieve singularity with the help of the modern computational tools and systems to enable us to not only understand our individual values but also our collective self worth and purposes so that we may never feel challenged or remain unequal to the existential causes. From the biblical times to the present, we have been taught to separate ourselves from the world with the belief that the separation is an intellectual exercise devoid of connections to

How to Implement Deutsch’s Algorithm in Haskell

Written by Roman V. Dushkin

With this article I would like to continue the series of publications about the model of quantum computing . In the previous article I gave a brief introduction about reversibility of computing processes . Dear reader, today I invite you to take a look at one of the simplest quantum algorithms, which shows the increase of efficiency in comparison with classical computing model. I am talking about Deutsch’s algorithm. We are also going to use Haskell to illustrate the approach and the Deutsch’s algorithm itself. We will cover the fundamentals of the model of quantum computing and compare the classical and the quantum implementations of Deutsch’s algorithm. Also, you will finally understand the essence of quantum computations. So if someone is interested in this issue — you're welcome to join the journey. Some History and a bit of Theory In 1985, David Deutsch developed one of the first quantum algorithms.

Using the Quick Raise of Matrices to a Power to Write a Very Fast Interpreter of a Simple Programming Language

Written by Alex Skidanov

Hello! My name is Alex Skidanov. Currently I work at MemSQL . I have recently read an article about calculating the Nth Fibonacci number in O(log N) arithmetic operations. But why would we need it in practice? — you may ask. By itself, the calculation N-th Fibonacci number may not be very interesting, but the approach with the matrices used in the article, in practice, can be applied to a much wider range of tasks. In the course of this article we will examine how to write an interpreter that can perform simple operations (assignment, addition, subtraction and truncated multiplication) on a limited number of variables with nested loops with an arbitrary number of iterations in a fraction of a second (of course, if the intermediate values in the calculations will remain in reasonable limits). For example, here is a code passed to the input of an interpreter: loop

A Few Words About Reversible Computing

Written by Roman V. Dushkin

Today I would like to raise a topic that has recently become all the more relevant and interesting. At least, judging by all the increasing number of publications in this direction, the interest in it is really growing. I am talking about quantum computing, or, to be more accurate, about a model of quantum computations. Without going into details of the model, let’s take a look at one of numerous questions related to it. We are going to review reversible computing . Further discussion will be held with the use of examples written in Haskell. To my mind, functional programming is much closer to the model of quantum computations than any other type. Let me leave out the reasoning of my point of view. But to understand the model of quantum computations, we need a much more severe paradigm shift, than, say, a shift from structured programming to object-oriented

IPv6 in Practice

Written by amarao

IPv6 for Cloud Servers Frankly speaking, the Internet lion’s share operates on IPv4. There are some living islands of IPv6 in Asia, plus several big sites, (such as google.com, facebook.com) respond via IPv6. But it’s better to use IPv6. The more websites will be ready to operate using IPv6, the easier and simpler conversion will be. Thus, it’s a relevant investment in the future. What does IPv6 mean for a particular cloud server from a practical point of view? IPv4 users will keep visiting websites that use IPv4 IPv6 users will be able to go to IPv6 server address only if this address is specified in DNS (AAAA record) Outgoing connections from a server to IPv4-only nodes will use IPv4 Outgoing connections from a server to the nodes with IPv6 and IPv4 addresses will use IPv6 addresses There’s an unofficial competition between Cloud server services and the Сloud storage

Application Porno or the Way to Find Secrets in Mobile Applications

Written by Alexey Troshichev

I have recently read an interesting article about a team of researchers that downloaded and parsed the Android Playmarket. Then they analyzed hundreds of thousands of applications regarding the presence of secret tokens and passwords. Since the result of their work concerned the analysis of decompiled code under Android only, I decided to write about a research I did a year ago. I performed it not for Android only, but also for iOS applications. By the way, this research became an online tool, but I’ll tell you about it at the very end, when its meaning becomes obvious. Also, I presented some of the mentioned above things at Zero Nights conference. So, here it goes… Stores are the main Goal There’re a lot of information about the manual analysis of mobile applications. There are also a lot of test methods and check lists. But the bigger part of these

Java 8 vs Scala. The Difference in Approaches and Mutual Innovations

Written by Ruslan Shevchenko

I was really glad to find out that my presentation about Scala and Java 8 was retweeted more than other similar content. That’s why I decided to make some notes and tell you about it. We are going to talk about the difference between Scala and Java and say why each of them is important. There are mutual innovations. Each language has borrowed something from each other. The question is: do you have to learn Scala if there is Java available? Definitely! The more languages you know, the more professional you are. If we ever ask a Scala engineer about the principal differences between Scala and Java, he will not tell you all the nuances of lambda functions and traits. Instead, he will provide the following example: Java public class Person { private String firstName; private String lastName; String getFirstName() { return firstName; } void setFirstName(String firstName) { this.firstName

YAWNDB. Time Series Database Written in Erlang

Written by Pavel Abalihin

I work at Selectel and a lot of our clients, who are leasing dedicated servers, require the information about traffic consumption. Cloud server users need statistics of hardware and network resources use. As for cloud storage users, they need downloads statistics. The simplest way to provide statistic data is plotting. There are plenty of software solutions for analyzing statistic data with further visualization. We have been looking for an appropriate tool with high performance as a basic requirement. But let’s begin with some theoretical information first. Some Theory Each chart of online activities reflects changes of some parameters within defined period of time (a month, a week, a day, etc.). To create a chart we should process some statistic material representing a set of “time-value” pairs in a defined time period. Such material is called time-series. There are quite many software tools for analyzing time series. They have one

A Point Localization in a Polygon

Written by Nikolai Ershov

I have recently come across a post dedicated to solving the task of locating a point in a polygon: there is a polygon (a closed broken line with no self-intersections) and we are to determine, whether the given A point is inside the polygon or not. You may wonder, how such purely mathematic task can be related to the theory of algorithms. But it actually can. Localization is a classic task in computational geometry (do not confuse with computer graphics). To begin with, look at the picture on the right that depicts a polygon of Peano curve type [1]. Try to tell, whether the red point is inside or outside the polygon. We are going to review a simple variation of the given task, when the given polygon is convex. (adsbygoogle = window.adsbygoogle || []).push({}); It is clear that if a polygon is a triangle or a quadrangle, there

Building a Minimal Convex Hull

Written by Nikolai Ershov

Since I have recently become interested in convex hulls, I decided to go on telling you about the algorithmic geometry. Today we are going to review the building of the so-called minimal convex hulls . Though the picture on the right provides an exhaustive explanation of what they actually are, you will find more formal definitions and two classical examples below. Minimal Convex Hull Notion Let the plane have a given finite number of A points. The hull of this set is any closed line H with no self-intersections, so that all A points are within this line. If H is convex (for example, any tangent to this line does not intersect it in any point), the corresponding hull is also named convex. Finally, a minimal convex hull is a convex hull of the minimal length (minimal perimeter). I have not checked (I guess it can be proved by

Erlang for the Little Ones. The Basic Syntax of Functions

Written by Victor Pikaev

Dear %username% , Let’s continue learning Erlang for the little ones. In the previous post we’ve reviewed the way of declaring functions and uniting them into modules. In this post we’ll consider the syntax of functions in details. The source code of all the examples in this post is here . Pattern Matching To begin with, let’s write a function that will greet a user and the welcome text will depend on user's gender. In the form of the pseudo code our function will look like the following: function greet(Gender,Name) if Gender == male then print("Hello, Mr. %s!", Name) else if Gender == female then print("Hello, Mrs. %s!", Name) else print("Hello, %s!", Name) end If we use pattern matching instead of the classic if then else construction, we can save plenty of the template code. That’s how this function will look in Erlang when using pattern matching: greet(male, Name)

Randomized Binary Search Trees

Written by Nikolai Ershov

I have always been surprised by the contrast between the grace of the main concept of binary search trees and implementation complexity of balanced Binary Search Trees ( Red-Black Trees , AVL Trees and Treaps). I have recently looked through the “Algorithms” by Robert Sedgewick [1] and found a description of randomized search trees (I’ve also found the original [2]). It is just one third of a page long (nodes insertion, and one more page for deletion). There’s also a nice implementation of the operation on deleting nodes from a search tree. Here we'll talk about randomized search trees, their implementation in C++ and also results of a small author’s research as for these trees balance. Let’s Go Step by Step Since I am going to describe a complete implementation of a tree, we’ll have to start from the very beginning (professionals can skip several paragraphs). Each node of

What is grep and How do We Use It?

Written by Simple Admin

When reading some articles about Unix commands, I noticed that the examples provided in them were not practically useful. It turns out that we do not know how to use tools that are actually useful. Before that Three years ago I was asked to hold an interview with applicants for the position of unix system administrator. There were eight applicants, and two of them were top-rated at the freelance marketplace. I never require sysadmins to know configs by heart. I think that we can always become familiar with the necessary software when needed. Of course, if we are ready to read much and want to use system tools properly. Therefore, I asked the applicants to solve the following tasks: create a cron job, that will be executed every even hour and at 3 o’clock; print the processor information from /var/run/dmesg.boot file. To my surprise, none of them coped with

KernelCare: Patching the Kernel On-the-Fly

Written by Andrey Yemelianov

As for today, we do not have to turn off and reboot a server with Linux operating system for months. But sooner or later, we’ll have to do it anyway. For example, to install kernel updates. As a rule, this procedure is a real pain for sysadmins. First of all, they have to choose time of the minimal user activity. They should also send out warning emails to all users in advance. Besides, there’s always a risk of an emergency when the server downtime can last for too long. There are also special programming solutions, with the help of which we can install patches and kernel updates without rebooting. As an example, we should name Ksplice – a product by Oracle Company, which is distributed under GPL v.2 license. It supports the following Linux distributives: Oracle, Linux, RHEL, Ubuntu (the desktop versions only) and Fedora. On the whole, Ksplice

Getting CSS Code in Order: Yandex Experience

Written by Beyond the Clouds

Hey there, I’m currently working at the front-end of a huge project – Yandex search results. As any other web project, we have a huge amount of CSS code and a considerable team interacting with it. When a lot of people write and edit CSS code with the help of various tools, it can become really complex and inconsistent. For instance, someone prefers writing vendor prefixes in one order, the other one prefers writing it in a different way. Some of them will use brackets round url, others won’t. When fixing some bug, someone could write, for example, position: relative at the beginning of the properties block without noticing that there’s already position: absolute somewhere between color and box-shadow . And he will keep wondering, why it’s not working. But despite the fact that we write the code in different ways, there’s a perfect order in our repository: CSS

A Cheat Sheet for HTTP Libraries in C++

Written by tangro

Unfortunately, standard C++ library provides no tools for working with HTTP protocol. Therefore, when we want to run some REST service, parse a webpage or write a simple bot or web crawler, we always wonder which library is better and faster in use. Sometimes a project already uses some framework (or even several). But how do we create an HTTP request using available facilities? Not to get confused each time performing such tasks, I decided to make a cheat sheet with examples of HTTP requests in C++ using different libraries. I guess Kukuruku is the best place for keeping such cheat sheets. We’re going to take a look at the following libraries: WinInet WinHttp Casablanca Qt POCO wxWidgets Boost.Asio libcurl neon .NET (С++/CLI) IXMLHTTPRequest HappyHttp cpp-netlib WinInet Website: http://msdn.microsoft.com/en-us/library/windows/desktop/aa385483(v=vs.85).aspx Platform: Windows 95 and later Example #include #include /// .... HINTERNET hIntSession = ::InternetOpen(_T("MyApp"), INTERNET_OPEN_TYPE_DIRECT, NULL, NULL, 0); HINTERNET

What is Rust for?

Written by Dzmitry Malyshau

Rust is a system programming language. It runs blazingly fast, prevents almost all crashes and removes the ambiguities associated with sharing access to data. Mozilla developed it as a tool to create a new generation browser engine – Servo . Similar Facilities The given language definition sounds like a fairy tale, since the henceforth tools have always balanced between speed and reliability. At one point, C++, in which speed and facilities are compensated by constant access errors outside the allocated memory to the reclamated memory. Or the unexpected results of reading data that is being written in-parallel by another thread. On the other hand, there’s Haskell, a “stronghold” language (on the principle “since it compiles, it operates”), which can’t brag about speed, though. Somewhere in-between balance Java, Python, C# and other popular (due to their usability) languages. As for me, Rust is a successful crossing of the best C++

Teaching the File System to Read

Written by kmu1990

What I’m Going to Tell You About In the previous article we constructed the environment needed to get familiar with the kernel. Then we took a look at loadable kernel modules and wrote a simple “Hello World!”. Finally, we wrote a simple and useless file system. Now it’s time to go on. The main aim of this article is to teach the file system to read from disk. For now it will read the operating information only (the super block and index nodes). Doesn’t seem like much, eh? The thing is that in this post we’ll have to define the structure of our file system – the way it will be stored on disk. Besides, we’ll also get familiar with SLAB and RCU. All of this will require some explanations – a lot of words and little code. Therefore, the post will be quite long. A Boring Beginning Our