How Can I Optimize C Vector Capacity for Read-Only Operations?

Optimizing Vector Capacity for Read-Only Operations

When working with vectors in C , there may be situations where you need to reduce their capacity after initially inserting values. This is especially relevant when the vector will be solely used for read operations subsequently.

To understand the concept, consider a vector that grows dynamically as values are inserted. However, once the values are filled, the vector may contain unused capacity, which can impact performance. While it's inefficient to repeatedly copy the data into a smaller vector, C 11 introduces a more efficient solution.

Utilizing std::vector::shrink_to_fit()

The non-binding function std::vector::shrink_to_fit() allows for a convenient reduction in vector capacity. As the draft standard states, this function requests the optimizer to reduce the capacity to match the size of the vector, without any guarantees.

In practice, this method often improves performance for read-only operations by reducing the overhead associated with unused capacity. It's a non-destructive operation that maintains the values within the vector and is supported by modern C compilers.

By implementing this technique, you can optimize the performance of your code while ensuring that the vector contains only the necessary capacity for read operations, without incurring the cost of additional copying.

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