Installation & Quick Start

ThreadPool-FP has no external dependencies. It uses only the Free Pascal run-time library and FCL, so installation is a search path, not a package hunt.

Requirements#

The library is CI-tested on Windows and Linux and follows Free Pascal's thread model, so it also works on macOS when cthreads is enabled (see Platform Requirements). There are no external package dependencies.

Install#

1. Add the unit search path to src/ (the library source), or install threadpool_fp.lpk in Lazarus.
2. Add ThreadPool.Simple to your uses clause.
3. Add ThreadPool.Tasks when you declare task or batch interface variables.

In Lazarus, open package/lazarus/threadpool_fp.lpk from the package manager and click Install. The package adds the library units to the compiler path automatically.

Quick start#

The smallest complete program:

program HelloThreadPool;

{$mode objfpc}{$H+}

uses
  {$IFDEF UNIX}
  cthreads, // must be first on Linux and macOS
  {$ENDIF}
  ThreadPool.Simple;

procedure ProcessItem(Index: Integer);
begin
  WriteLn('Processed item ', Index);
end;

var
  I: Integer;
begin
  for I := 1 to 5 do
    GlobalThreadPool.Queue(@ProcessItem, I);

  GlobalThreadPool.WaitForAll;
end.

Save this as HelloThreadPool.pas and compile with FPC only:

fpc -Fu./src HelloThreadPool.pas

Run it and you will see five lines such as:

Processed item 3
Processed item 1
Processed item 5
Processed item 2
Processed item 4

The five callbacks run across the pool's workers, so their output order may change between runs. That is expected and is the point: the callbacks run concurrently.

What just happened?#

• GlobalThreadPool is a ready-to-use process-wide pool owned by the unit. Do not free it; the unit manages its lifetime.
• Queue(@ProcessItem, I) enqueues one call that will run on a worker thread.
• GlobalThreadPool.WaitForAll blocks until every accepted callback has finished, so the program does not exit while work is still running.

Next steps#

• Beginner Guide — the same ideas in a longer sequence.
• Choose a Pool — when to use the bounded pool instead.
• Common Recipes — compiled, tested programs.

Build and test#

Build the package, tests, and run the suite:

lazbuild package/lazarus/threadpool_fp.lpk
lazbuild tests/TestRunner.lpi
./tests/TestRunner -a -p --format=plain

On Windows, run tests/TestRunner.exe in the final command.

The library and every example also build through the example build scripts (PowerShell on Windows, build-examples.sh on Linux) from the repository root:

.\build-examples.ps1

sh ./build-examples.sh

Executables are written to the ignored example-bin/ directory.

Sources of examples#

Copy the fully worked, compiled programs under Common Recipes, or browse the examples guide directory and the library README.