Limit max threads available to OpenVDB / TBB

[kdmarrett]

For a C++ library that uses OpenVDB as a dependency what is your recommended way of limiting the total # of threads that OpenVDB / TBB can spawn. I need a runtime user defined way to limit the max number of threads.

I'm not asking how to set the max # of threads for a given system .. that is already TBB's default.
I'd rather have a global solution (set at the begining of execution and forget) rather than having to wrap each openvdb call in a task arena. Note that tbb::task_scheduler_init is deprecated in recent TBB releases

Whats the recommended strategy?

I appreciate the help!

[Idclip]

You can use tbb/global_control to achieve this. Note though that this will affect all tbb execution in your application that links against the specified version from which the ::global_control symbol is called. Here's an example that we use in the vdb_ax binary:

openvdb/openvdb_cmd/vdb_ax/main.cc

Lines 782 to 786 in e7ec2a7

	std::unique_ptr<tbb::global_control> control;
	if (opts.mThreads.get() > 0) {
	axlog("[INFO] Initializing thread usage [" << opts.mThreads.get() << "]\n" << std::flush);
	control.reset(new tbb::global_control(tbb::global_control::max_allowed_parallelism, opts.mThreads.get()));
	}

If you're using other libraries which also use tbb but only want to control tbb utilisation in VDB, unfortunately the only** way is to wrap each call in an arena, as you've mentioned.

** you could also use multiple namespaced versions of tbb but this is probably a bit much