Should I Use `reserve()` or `resize()` for Preallocating Memory in C Vectors?

Memory Preallocation in Vectors: reserve() vs. resize()

In your scenario, you intend to pre-allocate memory for a vector member named t_Names with an initial size of 1000. Subsequently, you plan to increase its capacity by 100 when it reaches certain thresholds.

Regarding your choice between vector::resize() and vector::reserve(), they serve different purposes.

resize() modifies the vector's size by increasing or decreasing its capacity and setting the value of any new elements to the provided constructor argument (or to their default value if omitted). This means that you can directly access and iterate over these initialized elements.

On the other hand, reserve() merely allocates memory for the vector without initializing any elements. It does not affect the current size but increases the capacity. When you subsequently insert elements, there will be no reallocation necessary, as the memory was secured ahead of time.

In your case, based on the provided edit, it's recommended to avoid manual preallocation. Instead, rely on vector's automatic reallocation. It optimizes this process more efficiently than manual preallocation.

However, if you have a precise estimate of the required size in advance, consider using reserve() for initial preallocation. If necessary, the vector will handle additional reallocations as you insert more elements.

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