Are thread pools safe and is use of them recommended?

Question

I was researching the answer to this question and ran across this post. Is ThreadPool safe? How does ThreadPool compare with the OmniThreadLibrary? What are the pluses and minuses of using each?

Here is an example of what I am doing:

procedure DoWork(nameList: TList<Integer>)
var
  i: Integer;
  oneThread: PerNameThread;
begin
  for (i := 0; to nameList.Count-1) do
  begin
    oneThread := PerNameThread.Create(Self);
    oneThread.nameID = nameList[i];
    oneThread.Start();
  end
end;

I am creating a thread for each nameList item, and this could be up to 500 names. All these threads are too much, and slowing down the process, to the point where this process would be faster with just one thread.

Answer 1

First, you need to understand what a thread pool is.

A thread pool is a concept where you have a list of multiple threads that are suspended when they are not performing any tasks.

These threads are defined a bit differently than you are probably used to. Instead of them having all the necessary code inside their Execute() method, their Execute() method only contains a few lines of code to execute external code (giving the threads the ability to perform practically any processing that you require), take care of synchronizing the result back to the caller/UI, and returning the thread to the pool and putting it into a suspended state. When a new task is needed at a later time, a thread is given the task and resumed.
So by providing each thread with a method pointer for a task, you actually define what kind of job each thread will be processing each time it is run.

The main advantage of using a thread pool is that doing so avoids the overhead of creating and destroying a thread for each specific task.

As for OmniThreadLibrary, it is a full blown task management library. It uses its own thread pool and a pretty advanced task managing system that allows you to easily define which tasks can be executed in parallel, which tasks need to be executed in sequence, and which tasks have higher priority than others.

The only drawback of OmniThreadLibrary is that it is still limited to Windows only, so if you are thinking of providing multiplatform support for your application then you will have to find another solution.