Widestring 4545 times slower than unicodestring

I noticed that several people, in comments and in other blogs, compared the number of seconds that was spent for each benchmark in my previous post. I presented both the time spent, the number of iterations and the number of iterations per second, and it is the last number that is interesting. In order to fix that, I have now removed the time measurements from that post.

For that same reason, several people wondered why I did not like widestring. The main reason why I recommend not to use widestring is this one:

// approx. 25 million iterations per second
u:='';
for i:=0 to 100000000 do begin
  u:=u+' ';
end;

// approx. 0.0055 million iterations per second
w:='';
for i:=0 to 100000 do begin
  w:=w+' ';
end;

Note, how widestring is extremely slow for this specific test. This is the kind of stuff that can make a well made application perform really bad. A TCP/IP ping request between two servers on a good network uses less time than it takes to add a space to a widestring on my reasonably fast laptop.