How do I reserve capacity ahead of time with std::vector for large datasets?

When dealing with large datasets in C++, it is efficient to reserve the necessary capacity for a std::vector ahead of time. This avoids repeated memory allocations, which can enhance performance significantly.

To reserve capacity for a vector, you can use the reserve() method. This ensures that the vector has enough memory allocated for the specified number of elements, which helps in improving memory management.

Here’s a simple example demonstrating how to reserve capacity for a large dataset:

#include <iostream> #include <vector> int main() { std::vector myVector; // Reserve space for 10 million integers myVector.reserve(10000000); std::cout << "Reserved capacity for 10 million integers." << std::endl; // Now we can safely push back elements without worrying about performance hits for (int i = 0; i < 10000000; ++i) { myVector.push_back(i); } std::cout << "Successfully added 10 million elements." <> std::endl; return 0; }

C++ std::vector memory management reserve capacity performance optimization large datasets

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