Hi,

in an application of mine occurs a lot of string separation and re-concatenation. Since it is using masses of ANSI strings this is some performance problem.

The strings get stored and loaded from TStringList's and concatenated by simply using '+' and separated with the function copy().

What I'd like to know is: What's are fastest ways of handling ANSI strings?

Since I'm not good at reading assembler code I have to ask ... and yes, profiling is planned but not for tomorrow. ;)

TIA,
Marc

You could try to avoid repeated setlengths. However this would require two passes, something like

tot:=0;
for i:=0 to strlst.count-1 do  inc(tot,length(strlst[i]));
setlength(targetstring,tot);
j:=1;
for i:=0 to strlst.count-1 do
  begin
    move (targetstring[j],strlst[i]);
    inc(j,length(strlst[i]));
  end;

What I'd like to know is: What's are fastest ways of handling ANSI strings?

- avoid copying of strings if possible
- operate on pchar level in speed dependant parts.

Since I'm not good at reading assembler code I have to ask ... and yes, profiling is planned but not for tomorrow. ;)

Posting more code would help too.

It's hard to say in general; You would have to supply some example code.

if you're doing things like
  For I:=X to Y do
   S:=S+L[i];  // S string, L list.

then
It might be better to do

  Len:=0;
  For I:=X to Y do
    Inc(Len,Length(L[i]));  // S string, L list.
  SetLength(S,Len);
  P:=1;
  For I:=X to Y do
    begin
    T:=L[i];
    Len:=Length(T);
    Move(T[1],S[P],Len);
    inc(P,Len)
    end;

This will avoid a lot of calls to uniquestring, get/setlength etc.

Also, keep in mind that getting the I-th string from a list is an expensive operation.

So it is better to do
   T:=L[i];
   S:=Copy(T,X,Length(T)-X);
than to do
   S:=Copy(L[i],X,Length(L[i])-X);

The first option will call GetString only once, the second will call it twice.

This is the kind of thing you should pay attention to.

Michael.

Somewhat similar to that:

if (sl[4]  '') then
		if ((sl[4][1] = '"') AND (sl[4][length(sl[4])] = '"'))
			then BaseColor := copy(sl[4],2,length(sl[4])-2) else BaseColor :=
sl[4];

where BaseColor is a field of a class-type object, sl is a TStringList. I have to look for double quotes here and cut them out if necessary.

Sequences like this are heavily used in loading CSV files. This takes rather long on a 'small' cpu (Geode 300MHz).

Another snippet esecially for concatenation is this:

result := IntToStr(ID) + SEP +
IntToStr(ID_Customer) + SEP +
QT + Treatment + QT + SEP +
DateToStr(Date) + SEP +
QT + BaseColor + QT + SEP +
... and so on for approx. 15 fields

I think I'll try your technique here ...

This will help me, I'm sure. :)

Thank you so far,
Marc

So in general reserving buffer space and copying all string in and finally setting the length would be the way to go here, if I understand correctly.

Posting more code would help too.

See my other mail.

Thanks,
Marc

So in general reserving buffer space and copying all string in and finally setting the length would be the way to go here, if I understand correctly.

Yes, and avoid repeated use of stringlist[x]. First assign to a local var, then use for length() and normal use, as Michael already noted.

Hi,

You can tweak this a little by storing sl[4] and length(sl[4]) in local vars, but the whole approach tends to be slow. If you want it faster, dont allocate memory ("copy" & ":=" on the stack) and dont move string data. This could be done by "translating" BaseColor to an int or so. Either case you should not to use the StringList - read out BaseColor (and the other fields) directly from the source, skipping the " at reading.

Same as above - try to avoid the concatenation. What do you do with result? If you write it to a file, write it directly. If you echo it somewhere, echo it directly. If you pass it to another function, make it a record with pointers to the string data.

Leo

Leonhard Holz wrote

Hi,

Hi Leo,

I'm trying local temporary vars next, time measuring code is already in.

Since I'm lazy and love the TStringList since Delphi 1 I do not write at all myself but let the stringlist do it (saveToFile / loadFromFile). ;)

But I have to validate my habits anew in this case.

Thank you, I stand corrected,
Marc

This is the behavior you get using TStrings.Text property.

See TStrings.GetTextStr function

Luiz