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C++

C++ is a high-level programming language developed by Bjarne Stroustrup. But you know that, right?

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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.

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Lock-free Data Structures
I hope that this article will give a good start for a series of notes about lock-free data structures. I would like to share my experience with community, monitoring and thoughts about what lock-free structures are, how to implement them and whether the concepts of Standard Template Library (STL) containers are suitable for the lock-free containers, and when its worth to apply lock-free data structures.

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It is common practice not to like Windows. But, as a rule, phrase: “I haven't read the book but still condemn it” describes this situation well. Despite the tendency of not like Windows, there are still some things that are implemented well. I’d like to tell you about one of them.

I’ll review the embedded into OS implementation of the lock-free stack and its performance comparison with the cross-platform analogues.

The implementation of non-blocking stack on the basis of a singly linked list (Interlocked Singly Linked Lists, SList), has been available in WinAPI for quite a while. Operations on such list initializing and stack primitives over it have been implemented. Without going into details of implementing the SLists, the Microsoft just say that they use some non-blocking algorithm in order to implement atomic synchronization, increase performance and get rid of lock problems.

You can implement non-blocking singly linked lists by yourself. There are some articles written on the topic.
But there have been no 128-bit CAS operation before Windows 8. This fact caused problems when implementing such algorithms in 64-bit applications. SList helps to solve this task.

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Today I’m going to tell you about a new and a little known (to my mind) C++ feature — reference-qualified member functions. I’ll tell about the rules of such functions overloading and, as an example of use, I’ll show you that with the help of ref-qualified you can try to improve the resource management scheme, which is implemented with the help of another C++ idiom — RAII.

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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 parts: Basics, Inside and From Outside. Each article of the epic will refer to one of the parts. In the Basics I will tell about the low-level things, even about modern CPUs build. This part is for the whyers like me. In the Inside part I will cover interesting algorithms and methods of the lock-free world – it’s more likely a theory about how to implement a lock-free data structure. Libcds will be an endless source of the C++ code. From Outside will contain articles on libcds implementation practice, — programming solutions, advice and FAQ. From Outside is fed by the readers’ questions, comment, offers.

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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.

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Boost, A* Search algorithm, Boost.GraphIn the previous articles of the series we’ve reviewed the adaptive process of the square game field for concepts of boost graphs. Now we’ll consider the process of finding the path in the square field. Implementation of boost search allows adapting the algorithm quite accurately. In this article we’ll provide just one example of such parameterization – an ability to create various lengths of graph edges.

Let’s begin with describing the parameter. We should create a map of edge weights. This map will meet requirements of ReadablePropertyMapConcept concept. It’s quite easy to implement. We should define several types and [] iterator. On the basis of the key-type edge the latter returns its length.

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Boost.GraphI’ll briefly remind you of the task. There’s a two-dimensional game field consisting of squares. Some of them are vacant and others are occupied. We should find a path through vacant squares from one field position to another one. We implemented the search algorithm in Boost. But it requires our field to fit the graph definition. Or rather the class should meet the requirements of two concepts: boost::VertexListGraph and boost::IncidenceGraph. We don't want to change the interface of game field, as it’s not a graph for the remaining project and will never be one.

In the previous part we’ve reviewed attaching the external associative types that are necessary for interpreting the class as boost graph. Of course types only are not enough. We should also implement several functions with the assigned signature, and iterators which will help the library to handle the game field as a graph.

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Boost
I was always scared to use C++ templates due to the absence of standard mechanisms for setting parameter limits. In other words, when a developer writes the following function:

template <class T>
bool someFunc(T t)
{
    if (t.someCheck()) {
        t.someAction(0);
    }
}

it makes different assumptions as for the functionality of T type objects, but doesn’t have a standard facility to inform the user about them. Thus, the provided example can suppose at least the following things:

  1. T type objects are passed by value. So they should have on open copy constructor.
  2. There’s an open T::someCheck method with no parameters. It returns the value that is cast to bool type.
  3. There’s an open T::someAction method that can accept one parameter that is cast to numeric data type.

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