Associative Containers - A simple Performance Comparison

Before I take a deeper look insight the interface of the hash tables - officially called unordered associative containers - I will at first compare the performance of the associative containers. The best candidates are std::unordered_map and the ordered pendant std::map because both are used most frequently.

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Hash Tables

We missed the hash table in C++ for a long time. They promise to have constant access time. C++11 has hash tables in four variations. The official name is unordered associative containers. Unofficially, they are called dictionaries or just simple associative arrays. 

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Views: 108521

Type-Traits: Performance Matters

If you look carefully, you see, type-traits have a big optimization potential. The type-traits support in the first step to analyse the code at the compile-time and in the second step, to optimize the code based on that analysis. How is that possible? Dependent on the type of variable a faster variant of an algorithm will be chosen.

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constexpr Functions

constexpr functions are functions that can be executed at compile time. Sounds not so thrilling. But it is. Trust me. You can perform with constexpr functions a lot of calculations at compile time. Therefore, the result of the calculation is at runtime as a constant in ROM available. In addition, constexpr functions are implicitly inline.

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Tags: constexpr
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constexpr - Variables and Objects

If you declare a variable as constexpr the compiler will evaluate them at compile time. This holds not only true for built-in types but also for instantiations of user-defined types. There are a few serious restrictions for objects in order to evaluate them at compile time.

 

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Tags: constexpr
Views: 30441

Constant Expressions with constexpr

You can define with the keyword constexpr an expression that can be evaluated at compile time. constexpr can be used for variables, functions, and user-defined types. An expression that is evaluated at compile time has a lot of advantages. For example, constexpr variables and instances of user-defined types are automatically thread-safe and can be stored in ROM; constexpr functions that are evaluated at compile-time, are totally done with their work at run time.

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Tags: constexpr
Views: 13496

inline

Thanks to inline the compiler can replace the function call by the function body. There are two reasons to use inline functions: performance and safety.

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Tags: inline
Views: 16056

The Null Pointer Constant nullptr

The new null pointer nullptr cleans up in C++ with the ambiguity of the number 0 and the macro NULL.

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Tags: nullptr
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override and final

By using the context-sensitive keyword override and final you can explicitly manage the overriding of virtual functions. In particular, the keyword override solves a lot of issues with difficulty finding bugs in object hierarchies: Methods that should override methods of base classes. The result is a syntactically but not semantically correct program. The program performs the wrong stuff in the right way.

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Views: 53870

Strongly-Typed Enums

Enumerations are a convenient way to define integer constants with names. These integer constants are called enumerators. Sadly, classical enums have a few drawbacks.

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Tags: enum
Views: 43819

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