Why does the Map data structure in programming languages not preserve the order of elements?

In the Go language, the data structure map is implemented as a hash table, and it does not guarantee the preservation of element order during iteration. The reason is:

• To ensure high performance and efficient access, elements are stored in a hash table, where the order depends on the hash function and internal memory layout.
• Iteration over a map occurs in an arbitrary order, which can change with each traversal, to prevent code from relying on the order of elements.
• This is intentionally done so that programmers do not rely on the order of elements in a map and use slices or other data structures if order is important.

If an ordered dictionary is needed, a slice of keys, sorted separately, is usually used, for example:

m := map[string]int{"b": 2, "a": 1, "c": 3}
keys := make([]string, 0, len(m))
for k := range m {
    keys = append(keys, k)
}
sort.Strings(keys)
for _, k := range keys {
    fmt.Println(k, m[k])
}

Thus, the lack of order is a feature of the map implementation in Go, aimed at optimization and preventing errors.