id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
3794	StringRegExp - string passed by value instead by reference?	AspirinJunkie	Jon	"Script:
{{{
#!autoit
; create a very large string (should be about 400 MB because UTF-16 is used)
Global $sString = """"
For $i = 1 To 20 * 1024 * 1024
    $sString &= ""xxxxxxxxxx""
Next

; precompile pattern
StringRegExp("""", ""^."")

; determine time required for a small input string:
$iT = TimerInit()
StringRegExp(""Test"", ""^."")
ConsoleWrite(StringFormat(""RegEx with small input string: % 8.3f ms\n"", TimerDiff($iT)))

; determine time required for a large input string:
$iT = TimerInit()
StringRegExp($sString, ""^."")
ConsoleWrite(StringFormat(""RegEx with large input string: % 6.1f   ms\n"", TimerDiff($iT)))
}}}

Output:
{{{
RegEx with small input string:    0.012 ms
RegEx with large input string:  328.1   ms
}}}

The execution time depends directly on the size of the input string although only the first character of the string is processed.
If instead of StringRegExp a StringLeft or a StringMid is used then the execution times are independent of this.

This leads to the assumption that in the implementation of StringRegExp() at some point the input string is passed as ""by value"".
This would require the creation of a local copy of the string and would explain the loss of time.

If it is really a ""by value"" problem, i suggest to switch completely to ""by reference"" internally if possible. This would mean a massive performance gain for StringRegExp especially with large strings."	Feature Request	closed	3.3.15.6	AutoIt		None	Fixed	StringRegExp