Posts Tagged ‘C++11’

C++11: Multi-core Programming – PPL Parallel Aggregation Explained

August 17, 2013 6 comments

In the first part of this series we looked at general multi-threading and multi-core programming concepts without getting into the meat of any real problems, and in the second part we looked at the theory and application of the parallel aggregation pattern using either C++11’s standard thread library or Boost using classical parallel programming techniques. In this part we shall solve exactly the same summation problem from part 2 (adding all the numbers from 0 to 1 billion) but use the new Parallel Patterns Library (PPL) to do so. We will first look at a direct port using classical parallel programming techniques, then find out how to leverage new language features in C++11 which are employed by PPL to simplify the code and write parallel algorithms using an entirely new paradigm. We shall also look at some fundamental differences between PPL and other multi-threading/multi-core libraries, the pros and cons, and some gotchas to be aware of. Read more…

C++11 / Boost: Multi-threading – The Parallel Aggregation Pattern

August 15, 2013 8 comments

In the first part of this series we looked at general multi-threading and multi-core programming concepts without getting into the meat of any real problems. Tutorials on how to spin up worker threads in C(++) using POSIX/Pthreads, Windows or Boost.Thread are a dime a dozen so I won’t spend too much time on that here; instead I’ll look at a much less-documented and more complicated real-world multi-threading problem, namely that of parallel aggregation, and how to implement it both using new C++11 standard library functions, and with Boost.Thread for those who don’t have access to C++11 at present.

In the example developed in this article, we shall learn how to add all of the numbers from 0 to 1,000,000,000 (1 US billion) exclusive, using multi-threading on a multi-core system to speed up execution and make all the available cores work for us, rather than just one.

(do note that this particular problem can be solved very simply with the sum of a series formula: S = n(a1 + an) / 2 where S is the sum of the series, ax is the x‘th term in the series and n is the number of terms in the series; we are using the brute-force approach here purely for illustration)

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Visual Studio 2012 – Day 1 Annoyances (with an emphasis on C++)

February 19, 2013 3 comments

Update 21st February 2013: added information about Update 2, the C++11 Compiler November 2012 CTP (in two sections) and Find & Replace

Update 16th April 2013: the final version of Update 2 is now released; Update 1 is no longer needed (article updated)

So this is it, huh folks? 16 years of development, and the latest incarnation of the de-facto standard Windows development tool has an interface that might as well be from 1997. The compiler is not much better either it seems, as this C++11 feature support comparison shows: Visual Studio 2012 fails to include such basic support as initializer lists*, uniform initialization*, default and deleted constructors, inherited constructors and non-static data member initializers, while just about managing to shoehorn in raw string literals in the Update 1 package. Yet strangely, Microsoft managed to find time to implement SCARY iterators, checked iterators and futures and promises. SCARY iterators were only an optional part of the ratified C++11 standard.

But, the purpose of this article is to get your life in Visual Studio 2012 running smoothly, so let’s start with the basics.

* these features and others were added in the C++11 Compiler November 2012 CTP, see below Read more…

C++11: Using std::unique_ptr as a class member: initialization, move semantics and custom deleters

October 4, 2012 13 comments

Updated 23rd February 2013: Fixed typos in the code, incorrect use of const, clarified the use of the terms “initialization” and “assignment” to be semantically correct, corrected/clarified references to “constructor” and “assignment operator”, added an explanation of the default copy assignment operator and unique_ptr’s private copy constructor and copy assignment operator.

Updated 12th May 2013: Fixed a factual error regarding standard functions not working as custom deleters in all scenarios, fixed a factual error stating that std::shared_ptr doesn’t support custom deleters (it does), and corrected references to boost which should have referred to std. Expanded the custom deleter section with example cases of new’ing your own resource classes or fetching resources from an external API or factory function. Added text explaining the advantages of using the function object idiom for custom deleters.

The std::unique_ptr class is C++11’s replacement for the flawed std::auto_ptr smart pointer from C++03. std::unique_ptr provides single-ownership pointer semantics and is therefore especially useful when dealing with resource handles which should belong to a single object, and its custom deleter feature (which allows the call to delete to be replaced with an arbitrary function call when the object is destroyed, such as CloseHandle or IUnknown::Release) is great for ensuring resources are closed properly before their handles are freed.

I’m not going to explain how std::unique_ptr or move semantics work here – see the References section at the bottom for some introductory links – rather, I’m going to specifically look at how std::unique_ptr should be used in a non-copyable class (that is, one with a private, or – in C++ 11 – deleted, copy constructor), and specifically, how to make sure the resource is freed exactly and only once.

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C++11: About Lambda Functions

September 22, 2012 3 comments

One of my favourite inclusions in C++11 – the latest iteration of C++, formerly known as C++0x – is the ability to create lambda functions. Lambda functions are nothing more than unnamed, essentially anonymous functions that you can define in place of where you would usually use a function name, pointer or reference, and they come in particularly handy in combination with STL, although they are certainly not limited to that use. If you have become used to using Boost.Lambda in your applications, C++11’s lambda functions provide a more convenient syntax while also eliminating your code’s dependency on Boost.Lambda.

As with function pointers and references, lambda functions can be defined as variables, passed to and returned from other functions (including other lambda functions) and so on.

Ground Rules

Let us begin with a simple example comparing the use of C++11 and Boost.Lambda when iterating over a few numbers in an STL vector:

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