KUKURUKU HUB

2048 in Erlang

Written by peinguin

This article is about a WebSocket server on Erlang rather than about the game itself. I’ll tell you a small prehistory. When I began playing 2048 I couldn’t stop. It was to the detriment of both my job and family. So I decided that a bot should play instead of me. But the problem was that it’s a user game, there’s no global rating and it’s not comfortable to play without a browser. That’s why I decided to create the server part so that there would be rating and my bot could play without a browser. It’s my first project in Erlang. Many programmers are afraid of it. They suppose that it’s difficult to use it. But it’s actually not. I’ll try to highlight some things that are not obvious for Erlang beginners. I’ve hard coded a lot of things for simplicity. But anyway, I’ll be glad to read your

Masking a Class in Boost Graph. Part 1: Let the Interface Be

Written by Vadim Androsov

I had to rebuild a pathfinding algorithm for our game recently. The previous one ( Boost Concepts ) was bad as any sidestep was dangerous. So I wanted to take a ready algorithm from a good source. That’s exactly when I remembered about boost as there’s functionality for working with graphs. Unfortunately “find a function, call it and everything will work” approach wasn’t meant to be realized. The library is focused on the maximum use flexibility which has badly affected its simplicity. But it’s better than creating it from scratch (then fixing it). I didn’t want to bother with other libraries, while boost has already been used in the project. The following is given: a game field class with the following (significant for this article) interface: class GameField { public: GameField(); bool canPass(int x, int y) const; int getWidth() const; int getHeight() const; }; The field is a regular grid

Lightweight HTTP Server in less than 40 Lines on libevent and C++11

Written by NYM

Looking through programming articles sometimes I see posts about creating your own HTTP server. I am most interested in C++ so I often read blogs about it. After looking them through you could easily write you own web server “on sockets” using boost.asio or something else. I also examined libevent and libev. Each of them has its advantages. Libevent is of great interest to me for developing a small HTTP server. Considering some innovations in C++11 the code becomes much more space-efficient and allows for the creation of a basic HTTP server in less than 40 lines. (adsbygoogle = window.adsbygoogle || []).push({}); The information of this post will be useful for those not familiar with libevent and those who want to quickly create an HTTP server. There’s nothing innovative in this post, so you can use it as material for working in the right direction. libevent is better than

Lock-free Data Structures. The Inside. Memory Management Schemes

Written by khizmax

As I’ve already mentioned in the previous articles , the main difficulties when implementing lock-free data structures are ABA problem and memory reclamation. I will separate these two problems even though they are connected as there are algorithms that can solve only one of them. In this article I am going to review popular methods of safe memory reclamation for lock-free containers. I’ll demonstrate the application of one or another method of the classic lock-free queue by Michael-Scott [MS98]. Tagged pointers Tagged pointers is a scheme introduced by IBM for to solve the ABA problem. Perhaps, it’s the most popular algorithm for this problem’s solution. According to this scheme each pointer represents an atomic pair of the memory cell address and its tag (32-bit integer number). template struct tagged_ptr { T * ptr ; unsigned int tag ; tagged_ptr(): ptr(nullptr), tag(0) {} tagged_ptr( T * p ): ptr(p),

Brain Overclock or Internal Virtualization of Consciousness

Written by leon_3

Do you remember this movie? What is it doing here? Why the hell is such post on Kukuruku? I guess, because I think that the main component of IT is human, or rather our brain. I’ll tell you about another possibility of using your brain a bit more effectively. Everything described here has been tried out by me. It’s important to note that I’ll highlight if I haven’t tried something. I didn’t use any drugs or devices. Popular methods have only been used. And yes, it’s devastatingly realistic. Having tried it once, you'll never resist spreading the word. To avoid unnecessary cries in comments, I’m asking all staunch defenders of any religion or faith, and all the esoteric representatives to down-vote me and stop reading further. You’ll find no philosophy and great universal mysteries in this article. The rest of you are welcome — I’ll try to tell you about

Writing a File System in Linux Kernel

Written by kmu1990

Who This Article is for There are no complex or difficult concepts in this article, all required is a basic knowledge of the command line, the C language, Makefile and a general understanding about file systems. In this article I am going to describe the components necessary for development inside the Linux kernel, then we’ll write the simplest loadable kernel module and, finally, write a framework for the future file system. It’s a module that will register quite a useful (for now) file system in the kernel. The ones familiar with development inside Linux kernel may not find anything interesting here. Introduction A file system is one of the central OS subsystems. File systems continue to develop as operating systems evolve. Currently we have an entire heterogenetic zoo of file systems, from the old “classic” UFS , to the new exotic NILFS (though this idea isn’t new at all,

J Can be Readable

Written by AraneusAdoro

You must be kidding me! It’s like programming using regular expressions… You’ll never make me do that again! I’m looking at the code and feel like an idiot. Isn’t it really an esoteric language like brain fuck? Does anyone really use it? And such programs can be read afterwards? quicksort=: (($:@(<#[), (=#[), $:@(>#[)) ({~ ?@#)) ^: (1<#) Perl is a trifle against it. About J language J — is a Korean of programming languages (may look confusing). It’s an explosion in reserved characters factory. Plenty of brackets, periods, slashes and it even works. It must be magic or something. Wanting to be short or just having been carried away some people writing on J forget even simple rules of any code writing. These rules aren’t new but they acquire a critical meaning as applied to APL similar languages. As when reading ((]i.~[:{.[){([:{:[),]`([:<[$:[:>])@.([:32&=[:3!:0[:>]))«2 0 construction even a trained brain is at

Running and Software Development

Written by Michael Dubakov

What can running and software development have in common? Nothing special at fist glance. A sweaty and slender runner totally differs from a flabby, bent by scoliosis programmer. Stadiums don’t applaud to developers and no one gives them the country flag for the lap of honor round the office after some release. Nevertheless, running and development do have many things in common. I have read a very difficult book — Surfaces and Essences . Douglas Hofstadter had a blast and I didn’t want to read the book after the first 50 pages. I literally forced myself to read few dozens of pages per week until I read till the third book – then I loved it. This book is about the way people think. They think in terms of analogies. Using millions of examples, Hofstadter and Sander quite clearly bring out the way analogies work and the things you can

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

Using Go to Execute Commands on Hundreds of Servers with SSH

Written by youROCK

In this article we’re going to write a simple program on Go (100 lines), which will execute commands via SSH protocol on hundreds of servers, and will do it quite efficiently. It will be implemented with the help of go.crypto/ssh , which is SSH protocol implementation by authors of Go. More “advanced” version of the program written in this article is available on github: GoSSHa (Go SSH agent). Introduction The company I work for has more than one server and in order to keep the work efficient libpssh library on the basis of libssh2 has been written. This library was written on C with libevent use many years ago, and it still copes with its tasks. One thing is that it’s quite complicate to maintain it. Go language from Google is getting more popular, as well as within our company. So I decided to rewrite libpssh with Go and fix

JavaScript optimization challenge

Written by Няша Няшная

Hi, we're hosting the JS optimization challenge right now, with cash prizes and all. Link to full rules. The challenge: make JS strftime function very fast, and beat the performance of GNU libc's strftime . The slower code that can be used as a base for optimizations is here: github.com/mvasilkov/strftime You're free to use that source as the base of your solution. To make things interesting, we're not providing the reference benchmark. The benchmark will run on V8 (Node.js) engine. Send your solutions to [email protected] (as attachments, GitHub gists or whatever). Last date for submission is June 22, 2014. Winners will be announced on June 29.

Processes Paralleling to Speed up Computing and Tasks Execution in Linux

Written by XakepRU

Almost all PCs, released during the last few years, have had at least a dual core processor. So reader, if your PC isn’t extremely old or the bottom of the barrel budget brand, then most likely you are the owner of a multiple-processor system. Also if you like to play games, you should know you are utilizing potentially hundreds of GPU cores. But during the lion’s share of time all of these cores just gather dust. Let’s try to fix that. Introduction We rarely involve all the power of several processors (or cores) in order to solve every day problems. The high-end graphic engines are used for computer games only. I don’t like that. If I am working, why should my processors be resting? We should take on board all facilities and beauties of multi processors (multi cores) and parallelize everything possible. We should also use a heavy-duty video cards

Types Construction in Scala

Written by primetalk

When constructing “enterprise” systems it often turns out that ValueObjects (or case classes) are created. They store information about some instance of entity that is processed by the system. For example: case class Person(name: String, address: Address) This way of data representation in the system has two major strengths: Strictly typed access to the data; Capability of meta information binding to features with the help of annotations. And drawbacks: If there are many entities, the number of such classes also increases and their processing requires a lot of code of the same type (copy-paste); Meta information can be represented by annotations to the object features. But annotations facilities are limited and need reflection use; If the data should be represented not about all object features at once, it’s difficult to use the created classes; It’s also difficult to introduce a change of feature value (delta). We want to implement a framework that will allow creating new “classes” (types, types’ constructors, objects of the new types) incrementally using our own “bricks”. Using our own “bricks” production we can reach the

Introduction to Writing Tests with ScalaTest

Written by Kukuruku Hub

To be able to quickly start visualizing some of the tests that can be written with ScalaTest, we can take advantage of the test-patterns-scala template from the Typesafe Activator . It consists of a number of examples that essentially target the ScalaTest framework. The easiest way to get the code is to download the template bundle for test-patterns-scala. An archive contains a bootstrap script that can simplify our life's by starting Activator automatically. Setting up the test-patterns-scala activator project only requires you to go to the directory where you installed the Typesafe Activator and then, either start the GUI through the > activator ui command, or type > activator new to create a new project and select the appropriate template when prompted. Download the bundle Extract the downloaded zip file `cd` to test-patterns-scala directory from your console Run ./activator ui You can also generate the project by running: ./activator new

Mobile Typography

Written by Kukuruku Hub

As a designer you are probably keenly aware that more often than not, your dream font is not available on every device and every browser. Whether this knowledge is founded in the experience of designing and developing a site yourself, or from a horrifying experience such as your developer showing you the implementation of your design and feeling the special tug on your soul as part of you dies when viewing your original font choice rendered down into an abomination that makes comic-sans look vaguely desirable. Previously you may have even decided to give up the fight of using the perfect font for the entire site and opted to use it only on special portions of the design as an image. This, you tell yourself, will help you sleep at night and fix all the problems in the world as they can see the effort you have put into product

Transactional Memory: History and Development

Written by JIghtuse

Definition Parallel programming is difficult. When using systems with common memory, you can’t go without synchronization of parallel processes/threads access to the common resource (memory). The following are used for it: locks (mutex); lock-free algorithms (lockless); transactional memory. Transactional memory is a technology of concurrent threads synchronization. It simplifies the parallel programming by extracting instruction groups to atomic transactions. Concurrent threads operate paralleled till they start to modify the same memory chunk. For example, operations of nodes adding to the red/black tree (animation in the heading) can operate in parallel in several threads. /* Move item from one list to another */ int move(list *from, list *to) { __transaction_atomic { node *n = pop(from); push(to, n); } } Concurrency management approach with transactional memory use is called optimistic: we think that threads operate independently of one another and rarely change the same data. In this case most transactions are

N2O: Erlang Web Framework

Written by mag2000

Introduction This post implies a good intro into N2O . In order to learn about Erlang/OTP Web Framework N2O main features you should visit the github page or the official SynRC website . You will find there all the charts and presentations which you like so much. In this article I will cover the principles of framework operation. Version under consideration: N2O: 1.1.0. It’s always more interesting to see the result than to talk about it. I suggest that you install N2O to your PC first and then you will go deeply into its insides. It’s clearer that way. You can find answers to the arisen questions and recommendations at the official channel IRC #n2o at FreeNode.net. Installation Install Erlang if hasn’t been done yet. Download N2O, compile and run it. git clone git://github.com/5HT/n2o.git cd n2o/samples make && make console Look at: 127.0.0.1:8000/ Having opened a few windows you

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

Benchmarks: 14 Sorting Algorithms and PHP Arrays

Written by ahwoobachairiesaas

In this article I will tell you about the benchmark of sorting algorithms, written on PHP. There are 14 algorithms presented: quickSort countingSort combSort heapSort mergeSort shellSort selectionSort insertSort gnomeSort combinedBubbleSort cocktailSort bubbleSort oddEvenSort bubbleSortWithFlag Algorithms are not alphabetically ordered, but in order of their performance speed descending when sorting an array of 8 thousand elements. The following arrays dimensions, used for sorting, are presented: 1 100 200 400 600 800 1000 5000 10000 15000 20000 25000 30000 Each measurement was performed with different array filling, which is passed to sorting function. In the first case the array has been filled by random values with a (1, n) interval, in which n — is an array dimension. In the second case the array has been filled by random values with a (1, PHP_INT_MAX) interval, in which PHP_INT_MAX — is maximum variable value of INT type in the current system. In

Browser Extension to Extract the Text from Images

Written by alizar

Naptha — is a very useful Chrome extension. It automatically recognizes text of all the images that are downloaded by the browser. With the help of this extension you can edit images text, select, copy and translate it. This extension is indispensable for copying the text from the document scans, photographs, posters, diagrams, charts, screenshots and even memes. The idea to create this extension was born on the basis of xkcd meme. It showed the websites, which didn’t allow selecting the text at their web-pages. Ironically, xkcd website can also be referred to “violators” as it doesn’t allow selecting the text inside the memes. Naptha extension fixes this drawback. Developers say that the Stroke Width Transform algorithm, which is used in the extension, can recognize a text even of incoherent flourishes. This peculiarity can be considered as a bug or a feature. By the way, Naptha works for any

Mobile Responsive Design

Written by muhurov

When designing a mobile version of the site, the core question is still what resolution to choose and which are the most popular ones. Answering this question will help you to build the so-called «mobile responsive design» . By reference to statistics we will consider five the most popular mobile screen resolutions. And five the most popular tablet resolutions. How to Create Mobile Responsive Design? The media queries are entering the game. For instance, if we add the following code to the stylesheet, it will define the site background, provided that a certain device will have 480 or less pixels screen. @media screen and (max-device-width: 480px) and (orientation: portrait) { #background { width: 480px; background:url(/img/background.jpg); } } We can also use CSS-rule @import for the conditional loading of stylesheets into the current stylesheet. For example, the following code imports the phone.css , provided that a certain device will have

Lytro Company Announced a Plenoptic Camera of the Second Generation

Written by ilya42

Lytro Company, founded by Ren Ng from Stanford University, is commercializing plenoptic photography. It’s a photo of the light field when matrix with the help of micro lens system fixes not a 2D image but full information of the scene light field — you can focus such images right after the shooting, and photos taken by this camera allow you to get a stereo image. The first Lytro camera looked more like a cute toy and shots quality was not that high. After rendering it into a 2D image its resolution was just a few mega pixels. The second generation camera, named Lytro Illym , looks much more like a real camera in both appearance and features. The size of the sensor has been increased from 1/3" to 1", images resolution is 40 Megaray (it’s the measurement for plenoptic cameras) compared to 11 in the first Lytro. 2D images