During executing my multithreading program only 4 of the available 8 CPU's are being used. Why? What can I change to make all CPU's working?
Parallel.ForEach(0, CalcList.Count-1)
.NumTasks(nMax)
.NoWait
.Execute(
procedure(const value: integer)
begin
CalcUnit.EntrySearch(value);
end);
(nMax and the CalcList.Count are both 16, Intel I7 HyperThreaded)
Thank you
I just did a test on an i7 2600 (4 cores 8 HT) using OTL. A simple Parallel.ForEach loop makes use of all 8. With and without the .NumTasks that you have. There is no problem with the library.
begin
Parallel.ForEach(0, 100)
//.NumTasks(16)
.Execute(
procedure(const value: integer)
var
newValue: Single;
I: Integer;
begin
newValue := value;
for I := 1 to 100000000 do
begin
newValue := newValue * I;
newValue := newValue / I;
end;
end);
ShowMessage('Done!');
end;
My guess is that the problem is in your code. Disk accesses in threads are a good way to counter the benefits of using threads in the first place.
I don't know enough about your code but you should rather look at reading in the data in a single thread and then threading the actual processing of that data.
I see that you also have .NoWait specified. Are you saving the return value for your Parallel.ForEach? Its a good idea to save this value because otherwise your code will block when the OnClick exits. See gabr's answer to this question.