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Certain collection types in .NET have an optional "Initial Capacity" constructor parameter. For example:
Dictionary<string, string> something = new Dictionary<string, string>(20);
List<string> anything = new List<string>(50);
I can't seem to find what the default initial capacity is for these objects on MSDN.
If I know I will only be storing 12 or so items in a dictionary, doesn't it make sense to set the initial capacity to something like 20?
My reasoning is, assuming that the capacity grows like it does for a StringBuilder, which doubles each time the capacity is hit, and each reallocation is costly, why not preset the size to something you know will hold your data, with some extra room just in case? If the initial capacity is 100, and I know I will only need a dozen or so, it seems as though the rest of that memory is allocated for nothing.