Clone this repo:
  1. 178e3e0 Update prefix from master to main by Everton Constantino · 4 months ago upstream/master
  2. d0aac7e Add support for Windos on Arm builds on BUILD.bazel by Everton Constantino · 4 months ago
  3. 4fe0e1e Fix incorrect thread number used in 2D task with thread by Zhi An Ng · 9 months ago
  4. c5b96e3 Parallelize task 2D with thread id support by Zhi An Ng · 9 months ago
  5. 966fbf7 Parallelize task 1D with thread id support by Zhi An Ng · 9 months ago


BSD (2 clause) License Build Status

pthreadpool is a portable and efficient thread pool implementation. It provides similar functionality to #pragma omp parallel for, but with additional features.


  • C interface (C++-compatible).
  • 1D-6D loops with step parameters.
  • Run on user-specified or auto-detected number of threads.
  • Work-stealing scheduling for efficient work balancing.
  • Wait-free synchronization of work items.
  • Compatible with Linux (including Android), macOS, iOS, Windows, Emscripten environments.
  • 100% unit tests coverage.
  • Throughput and latency microbenchmarks.


The following example demonstates using the thread pool for parallel addition of two arrays:

static void add_arrays(struct array_addition_context* context, size_t i) {
  context->sum[i] = context->augend[i] + context->addend[i];

#define ARRAY_SIZE 4

int main() {
  double augend[ARRAY_SIZE] = { 1.0, 2.0, 4.0, -5.0 };
  double addend[ARRAY_SIZE] = { 0.25, -1.75, 0.0, 0.5 };
  double sum[ARRAY_SIZE];

  pthreadpool_t threadpool = pthreadpool_create(0);
  assert(threadpool != NULL);

  const size_t threads_count = pthreadpool_get_threads_count(threadpool);
  printf("Created thread pool with %zu threads\n", threads_count);

  struct array_addition_context context = { augend, addend, sum };
    (pthreadpool_task_1d_t) add_arrays,
    (void*) &context,

  threadpool = NULL;

  printf("%8s\t%.2lf\t%.2lf\t%.2lf\t%.2lf\n", "Augend",
    augend[0], augend[1], augend[2], augend[3]);
  printf("%8s\t%.2lf\t%.2lf\t%.2lf\t%.2lf\n", "Addend",
    addend[0], addend[1], addend[2], addend[3]);
  printf("%8s\t%.2lf\t%.2lf\t%.2lf\t%.2lf\n", "Sum",
    sum[0], sum[1], sum[2], sum[3]);

  return 0;