Function set_group_affinity

Source/astcenccli_platform_dependents.cpp:88–124

* @brief Manually set CPU group and thread affinity. * * This is needed on Windows 10 or older to allow benefit from large core count * systems with more than 64 logical CPUs. The assignment is skipped on systems * with a single processor group, as it is not necessary. */

 * with a single processor group, as it is not necessary.
 */
static void set_group_affinity(
	pthread_t thread,
	int thread_index
) {
	// Skip thread assignment for hardware with a single CPU group
	int group_count = GetActiveProcessorGroupCount();
	if (group_count == 1)
	{
		return;
	}

	// Ensure we have a valid assign if user creates more threads than cores
	int assign_index = thread_index % get_cpu_count();
	int assign_group { 0 };
	int assign_group_cpu_count { 0 };

	// Determine which core group and core in the group to use for this thread
	int group_cpu_count_sum { 0 };
	for (int group = 0; group < group_count; group++)
	{
		int group_cpu_count = static_cast<int>(GetMaximumProcessorCount(group));
		group_cpu_count_sum += group_cpu_count;

		if (assign_index < group_cpu_count_sum)
		{
			assign_group = group;
			assign_group_cpu_count = group_cpu_count;
			break;
		}
	}

	// Set the affinity to the assigned group, and all supported cores
	GROUP_AFFINITY affinity {};
	affinity.Mask = (1 << assign_group_cpu_count) - 1;
	affinity.Group = assign_group;
	SetThreadGroupAffinity(thread, &affinity, nullptr);
}

/**
 * @brief Proxy Windows @c WaitForSingleObject underneath a pthreads-like wrapper.