digitalmars.D - Re: dynamic array memory allocation
- martin <m_dot_hinsch rug.nl> May 16 2007
davidl Wrote:It's useful. Seperating the concept of capacity and length should be considered carefullyI find myself wondering what actually happens when I create a dynamic array and concatenate items onto it. I think I read in a post that memory will be over-allocated at times to avoid re-allocating. I think it would help out a lot to have an ability to specify over-allocation. Something like uint a = ; a.length = 3:10 Where the array length is 3, but you are guaranteed to have memory allocation for 10, so you can be guaranteed that concatenation up to ten will not need to allocate memory. This could help in the situation where there is concatenation in a loop, and the programmer over-sizes the array before the loop and re-sizes after the loop.
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I can immediately give an example for the usefulness of this from my field: I'm doing individual-based simulations with many individuals (I'm a theoretical biologist). Typically these individuals reproduce frequently which often involves filling a new array with an unknown number of new objects (if you have discrete generations) or alternatively adding (an unknown number of) objects to an existing array. In C++ being able to do .reserve(large_enough_number) can improve performance considerably. Martin
May 16 2007