Hash Functions

The reason for the constant access time (best cast) of the unordered associative containers are the hash functions. As ever, C++ offers a lot of ways to adjust the behaviour of the hash functions. On one hand, C++ has a lot of different hash functions; on the other hand, you can define your one hash function. You can even adjust the number of buckets.

Read more
Comments 1Views: 5108

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.

Read more
Add CommentViews: 4124

Hash Tables

We missed 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. 

Read more
Comments 4Views: 3111

Type-Traits: Performance Matters

If you look carefully, you see, type-traits have a big optimization potential. The type-traits support it 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 a variable a faster variant of an algorithm will be chosen.

Read more
Add CommentViews: 2441

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 implicit inline.

Read more
Tags: constexpr
Add CommentViews: 1420

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.

 

Read more
Tags: constexpr
Comments 6Views: 1661

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.

Read more
Tags: constexpr
Comments 2Views: 905

Support my blog by buying my E-book

Latest comments

Modernes C++

Subscribe to the newsletter

Including two chapters of my e-book
Introduction and Multithreading

Blog archive

Source Code

Visitors

Today 572

All 219842

Currently are 104 guests and no members online