Kui suur on massiivi kogumälu, sõltuvalt selle lisatud elementide arvust ja tüübist?

The total memory occupied by an array roughly consists of:

1. Overhead costs of the array itself: Swift's internal structures for managing the array (such as reference counting, capacity, and size information). These overheads are fixed or depend on capacity.

2. Memory used by the elements: depends on the number of elements and the type of each element.

   • Value types: for example, Int, Double, Struct. Each instance stores its data directly within the array. The memory size for an element equals the size of the type.

     // Size of Int32 is 4 bytes on a 64-bit architecture
     let intSize = MemoryLayout<Int32>.size // 4
     

   • Reference types: for example, Class, String (for long strings), closures. The array only stores references to objects. The memory size for an element equals the size of the reference (usually 8 bytes on a 64-bit architecture). The objects themselves are stored on the heap, and their size does not directly affect the array's memory.

     // Size of a reference to an object (e.g., an instance of a class)
     let referenceSize = MemoryLayout<AnyObject>.size // 8 on 64-bit
     

The approximate formula looks like this:

Total memory ≈ Array overhead + (Number of elements * Size of each element)

The size of an element for value types is MemoryLayout<ElementType>.size. For reference types, it is MemoryLayout<AnyObject>.size.

It is also important to consider the array's capacity expansion mechanism: when the array reaches its current capacity, Swift typically allocates a new, larger block of memory (for example, twice as large) and copies the existing elements into it. This results in a temporary increase in memory consumption during the expansion operation and potentially unused memory (capacity - count).