= Performance =

Implementation of Universal_String use several techniques to speedup performance and minimize memory footprint:

 - string data stored in UTF-16 encoded form internally, so it occupies two times less memory then Wide_Wide_String for most modern languages.

 - use of implicit sharing (also known as copy-on-write) technology allows Universal_String to have constant time of assignment operation.

 - use of atomic operations to handle reference counter makes Universal_String as safe in multitasking context as other Ada types.

 - use of special algorithms and utilization of SIMD operations (when available) significantly improve performance.

== Performance comparison ==

Here is comparison of performance between Ada.Strings.Wide_Unbounded and League.Strings packages. Number is a speedup of operations on Universal_String comparing to corresponding operation on Unbounded_Wide_String.

|| Operation                      || GNAT GPL 2010/League        || GNAT GPL 2010/League        ||
||                                || (portable, 64 bits)         || (x86_64)                    ||
||                                || (1/10/100/1000/10000 bytes) || (1/10/100/1000/10000 bytes) ||
|| Object initialization          || 1.57                        || 1.53                        ||
|| Assignment of empty string     || 1.91                        || 1.84                        ||
|| Assignment of non-empty string || 1.03                        || 1.06                        ||
|| Compare for equality           || 4.63/6.40/9.46/11.76/11.88  || 4.12/6.56/15.49/19.95/15.09 ||
|| Compare for less               || 1.16/1.02/1.56/1.50/1.50    || 1.08/1.09/2.55/3.55/2.79    ||
|| Append of string               || 1.30                        || 1.30                        ||