static void build()

in src/annoylib.h [1537:1562]

• 20 lines of code
• 5 McCabe index (conditional complexity)

  static void build(AnnoyIndex<S, T, D, Random, AnnoyIndexMultiThreadedBuildPolicy>* annoy, int q, int n_threads) {
    AnnoyIndexMultiThreadedBuildPolicy threaded_build_policy;
    if (n_threads == -1) {
      // If the hardware_concurrency() value is not well defined or not computable, it returns 0.
      // We guard against this by using at least 1 thread.
      n_threads = std::max(1, (int)std::thread::hardware_concurrency());
    }

    vector<std::thread> threads(n_threads);

    for (int thread_idx = 0; thread_idx < n_threads; thread_idx++) {
      int trees_per_thread = q == -1 ? -1 : (int)floor((q + thread_idx) / n_threads);

      threads[thread_idx] = std::thread(
        &AnnoyIndex<S, T, D, Random, AnnoyIndexMultiThreadedBuildPolicy>::thread_build,
        annoy,
        trees_per_thread,
        thread_idx,
        std::ref(threaded_build_policy)
      );
    }

    for (auto& thread : threads) {
      thread.join();
    }
  }