When building a simple TTimer demo I cannot seem to get it working

Any idea what the problem could be if you paste this code into your form with a memo?

var
   TimeSpent: integer;
procedure TForm2.Button1Click(Sender: TObject);
var
   i, answer: integer;
begin
   Timer1.enabled := false;
   TimeSpent := 0;
   Timer1.Enabled := true;
   Timer1.interval := 1;
   for i := 0 to 999999999 do
   begin
     answer := i * answer;
   end;
   memo1.lines.add('time spent: ' + inttostr(timespent));
end;
procedure TForm2.Timer1Timer(Sender: TObject);
begin
   inc(TimeSpent);
end;

It says
time spent: 0
Whereas the time should be a lot.

Regards,
Lars

El 18/10/20 a les 19:18, Lars via lazarus ha escrit:

No, since your loop is busy waiting the Timer1Timer method is never fired. Events are only processed in the main gui loop. You could add an "Application.Processmessages" inside your loop but you must know what you are doing (e.g. you could click again button1 and that's not desirable).

Bye

I don't know what are you trying to do, but if you are trying to find out how long it takes certain process, you should try other approach. Timer is low precision and it is only fired by events, so you must process event's queue.

A first and bad approach:

for i := 0 to 999999999 do
begin
    answer := i * answer;
    application.processmessages; //<-- process event queue
end;

But this is very not a very efficient way. The best is to get the start time, get the end time and subtract.

var
   StartTime,EndTime:TDataTime;
   i, answer: integer;
begin
  StartTime:=now;
  for i := 0 to 999999999 do
  begin
     answer := i * answer;
  end;
  EndTime:=now;
  memo1.lines.add('time spent: ' + TimeToStr(EndTime-StarTime) );
end;

But TDateTime is not accurate at all if you are measuring short periods (milliseconds).

EpikTimer is a component with much better precision.

https://wiki.lazarus.freepascal.org/EpikTimer

The problem of your code is that the variable <answer> is not initialized. Regards
Evgueny

вт, 27 окт. 2020 г. в 15:28, Santiago A. via lazarus <

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The first multiplication is when i = 0, so it should be ok. I am wondering though, the OP wants to calculate the factorial of 999999999. That would require a larger data type than an integer to store the result in! ;)

On Tue, Oct 27, 2020 at 1:46 PM Евгений Кадисов via lazarus <

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var
  StartTime,EndTime: Int64;
  i, answer: integer;
begin
  answer := 1;
  StartTime := GetTickCount64;
  for i := 0 to 999999999 do
  begin
    answer := i * answer; //What does this really do?
  end;
  EndTime := GetTickCount64;
  memo1.lines.add('ms spent: ' + IntToStr(EndTime-StartTime));
end;

Now() is an extremely bad time source since it is really only fairly accurate to seconds. It also uses floating point so it is rounding. Int64 holds the same bumber of bits as a double but all of it is dedicated to the number.