On Friday 29 September 2006 04:57, Graeme Geldenhuys wrote:
>
> Below is a text (console) thread demo. The one thread counts from 0 to
> 1k and the other thread counts down from 1k to 0. Again, under Linux,
> one thread executes and teminates, then the next thread executes and
> terminates.
Greetings, Graeme.
I think I see the problem. On today's fast machines, a count of 1000 just
isn't enough processing for a meaningful test, at least not under Linux. I
really don't know much about Windows, but my conjecture is that perhaps under
that system the function calls to write the output cause the other thread to
receive processing time.
The following modified version of your program shows that threads work under
Linux. The execute loops have been modified to continually count up/down (as
appropriate) until terminated. The RunNow procedure was modified to let the
threads run for three seconds before terminating them itself, and the
FThreadCount thing was taken out (along with the OnTerminate handlers).
To properly see the output, you should redirect it to a file, unless you
really have a LOT of scrollback buffer set up. :-) On my Athlon XP 2200 I
get a file 35.5 megabytes in size!
~/tmp $./demo1 > demo1.txt
~/tmp $ls -l demo1.txt
-rw-r--r-- 1 pcervasio users 39566886 2006-10-02 12:31 demo1.txt
After looking at the contents of demo1.txt, I can see that the increment
thread actually got to its eleventh count up before the decrement thread got
its first share of time. This should help explain why in your original
program it appeared that one thread was executing to completion before the
other... it WAS, but only because there wasn't enough to do.
The above was done using version 2.04 of the compiler on a Slackware 10.1
machine with a 2.4.32 kernel. I appear to get similar results on my 2.6.17.6
box after copying the executable over (running an Athlon 2600). The
decrementor first shows up after incrementor loop 15. The redirected output
file is 53 megabytes, though... much bigger than I expected from the machine
speed difference alone.
I hope this is helpful.
Best regards,
Pete C.
---------------------------------------
program demo1a;
{$mode objfpc}{$H+}
uses
{$IFDEF UNIX}
{$IFDEF UseCThreads}
cthreads,
{$ENDIF}
{$ENDIF}
Classes, SysUtils;
type
// counts up till 1k until terminated
TIncrementer = class(TThread)
protected
procedure Execute; override;
end;
// counts down from 1k until terminated
TDecrementer = class(TThread)
protected
procedure Execute; override;
end;
TRunThreads = class(TObject)
private
t1, t2: TThread;
public
constructor Create;
procedure RunNow;
end;
{ TRunThreads }
constructor TRunThreads.Create;
begin
t1 := TIncrementer.Create(True);
t1.Priority := tpLower;
t1.FreeOnTerminate := True;
t2 := TDecrementer.Create(True);
t2.Priority := tpLower;
t2.FreeOnTerminate := True;
end;
procedure TRunThreads.RunNow;
var
donetime: TDateTime;
begin
{ run for 3 seconds }
donetime := now + encodetime(0, 0, 3, 0);
writeln('RunNow');
t1.Resume;
t2.Resume;
repeat
sleep (100);
until now > donetime;
t1.terminate;
t2.terminate;
sleep (10); { give threads a chance to end }
WriteLn('All threads completed!');
end;
{ TIncrementer }
procedure TIncrementer.Execute;
var
i, j: integer;
begin
j := 0;
while not terminated do
begin
writeln (ClassName, ': --- Loop ', j);
for i := 0 to 1000 do
begin
if terminated then break;
Writeln(Classname, ': ', i);
end;
end;
end;
{ TDecrementer }
procedure TDecrementer.Execute;
var
i, j: integer;
begin
j := 0;
while not terminated do
begin
writeln (ClassName, ': --- Loop ', j);
for i := 1000 downto 0 do
begin
if terminated then break;
Writeln(Classname, ': ', i);
end;
end;
end;
var
lRunThreads: TRunThreads;
begin
lRunThreads := TRunThreads.Create;
lRunThreads.RunNow;
writeln('Done...');
end.
---------------------------------------
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