


`std::vector::reserve()` vs. `std::vector::resize()`: When to Use Which for Efficient Memory Management?
Dec 21, 2024 am 03:46 AMstd::vector::resize() vs. std::vector::reserve()
In C , std::vector is a commonly used container for storing elements of the same type. It offers two methods, std::vector::reserve() and std::vector::resize(), that play distinct roles in memory management.
std::vector::reserve()
- Allocates memory for a specified number of elements without modifying the logical size of the vector.
- Ensures that future push_backs or inserts can be accommodated without reallocating memory.
- Does not resize the vector or modify its elements.
std::vector::resize()
- Resizes the vector to a specified size, adding or removing elements as needed.
- Initializes newly added elements with their default values.
- Can cause the vector's memory to be reallocated, potentially invalidating existing references, iterators, or pointers.
Application in the Provided Code
In the given sample code, the member vector my_member is initially allocated memory for n_dim elements using std::vector::reserve(). However, no elements are initialized, and accessing elements beyond the current logical size (0) would result in undefined behavior or errors.
To write elements to the vector, std::vector::resize() should be used. It would resize the vector to n_dim and initialize all elements to zero in this case.
VS2010 SP1 Behavior
The test code provided fails in debug builds with VS2010 SP1 because it attempts to access element 5 of a vector with only a logical size of 0. This is considered undefined behavior and results in a crash in debug mode.
Conclusion
Based on the provided information, it is correct to use std::vector::resize() when elements need to be written to the vector. std::vector::reserve() should be used when it is known that future insertions will occur and memory should be reserved for them in advance, but element values do not need to be initialized upfront.
The above is the detailed content of `std::vector::reserve()` vs. `std::vector::resize()`: When to Use Which for Efficient Memory Management?. For more information, please follow other related articles on the PHP Chinese website!

Hot AI Tools

Undress AI Tool
Undress images for free

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Notepad++7.3.1
Easy-to-use and free code editor

SublimeText3 Chinese version
Chinese version, very easy to use

Zend Studio 13.0.1
Powerful PHP integrated development environment

Dreamweaver CS6
Visual web development tools

SublimeText3 Mac version
God-level code editing software (SublimeText3)

Hot Topics

Yes, function overloading is a polymorphic form in C, specifically compile-time polymorphism. 1. Function overload allows multiple functions with the same name but different parameter lists. 2. The compiler decides which function to call at compile time based on the provided parameters. 3. Unlike runtime polymorphism, function overloading has no extra overhead at runtime, and is simple to implement but less flexible.

C has two main polymorphic types: compile-time polymorphism and run-time polymorphism. 1. Compilation-time polymorphism is implemented through function overloading and templates, providing high efficiency but may lead to code bloating. 2. Runtime polymorphism is implemented through virtual functions and inheritance, providing flexibility but performance overhead.

Yes, polymorphisms in C are very useful. 1) It provides flexibility to allow easy addition of new types; 2) promotes code reuse and reduces duplication; 3) simplifies maintenance, making the code easier to expand and adapt to changes. Despite performance and memory management challenges, its advantages are particularly significant in complex systems.

C destructorscanleadtoseveralcommonerrors.Toavoidthem:1)Preventdoubledeletionbysettingpointerstonullptrorusingsmartpointers.2)Handleexceptionsindestructorsbycatchingandloggingthem.3)Usevirtualdestructorsinbaseclassesforproperpolymorphicdestruction.4

Polymorphisms in C are divided into runtime polymorphisms and compile-time polymorphisms. 1. Runtime polymorphism is implemented through virtual functions, allowing the correct method to be called dynamically at runtime. 2. Compilation-time polymorphism is implemented through function overloading and templates, providing higher performance and flexibility.

People who study Python transfer to C The most direct confusion is: Why can't you write like Python? Because C, although the syntax is more complex, provides underlying control capabilities and performance advantages. 1. In terms of syntax structure, C uses curly braces {} instead of indentation to organize code blocks, and variable types must be explicitly declared; 2. In terms of type system and memory management, C does not have an automatic garbage collection mechanism, and needs to manually manage memory and pay attention to releasing resources. RAII technology can assist resource management; 3. In functions and class definitions, C needs to explicitly access modifiers, constructors and destructors, and supports advanced functions such as operator overloading; 4. In terms of standard libraries, STL provides powerful containers and algorithms, but needs to adapt to generic programming ideas; 5

C polymorphismincludescompile-time,runtime,andtemplatepolymorphism.1)Compile-timepolymorphismusesfunctionandoperatoroverloadingforefficiency.2)Runtimepolymorphismemploysvirtualfunctionsforflexibility.3)Templatepolymorphismenablesgenericprogrammingfo

C polymorphismisuniqueduetoitscombinationofcompile-timeandruntimepolymorphism,allowingforbothefficiencyandflexibility.Toharnessitspowerstylishly:1)Usesmartpointerslikestd::unique_ptrformemorymanagement,2)Ensurebaseclasseshavevirtualdestructors,3)Emp
