Understading OpenVINO+OpenCV thread affinity in Hyper-Threaded systems

[afdl]

Hello,

I'm doing some experiments with OpenVINO and OpenCV Stereo Matching algorithms (https://docs.opencv.org/3.4.3/dd/d86/group__stereo.html). My code is using the OpenCV 3.4.3 distribution from OpenVINO 2018 R3. I'm working on Windows 10 platform compiling with Visual Studio 2017 x64.

My CPU is a 7th gen Intel Core: 4 cores with HyperThreading enabled, so 8 logical cores.

While I'm pretty confident with OpenCV, I'm less prepared on OpenVINO and the way you "customize" the thread affinity of the process. I have some questions:

- OpenCV matching algorithms use parallel computing (I see it while running since they runs on all 8 cores), is OpenMP involved here?
- My goal is to tell the program to parallelize using only cores 1,3,5,7 (so "half" of all hyper-threaded cores). Should I use a combination of OMP_PROC_BIND, OMP_NUM_THREADS (I would set it to 4), OMP_PLACES environment vars?
What could be the correct setup? example:

• OMP_NUM_THREADS=4
• OMP_PROC_BIND=true
• OMP_PLACES={1,3,5,7}

- Are these environment vars used at compile time, or run time? In other words, can I test the different configurations without recompiling the program?

Thanks for the support

[Shubha_R_Intel]

Dear afdl,

you are using an ancient version of OpenVino - the product has vastly improved since OpenVINO 2018 R3 ! Please upgrade to the latest, just released this week - 2019 R1. I believe this blog article will answer many of your questions ! https://software.intel.com/en-us/blogs/2019/04/02/improved-parallelization-extended-deep-learning-capabilities-in-intel-distribution

And what that blog article will tell you is that OpenVino starting 2019 R1 is using TBB by default now, not OpenMP.

Thanks,

Shubha

[Francesconi__Alessan]

Thanks Shubha, I'm aware of the 2019 release and I will give it a try later those days, but for this particular work I need to stick with 2018 R3 for a couple of reasons.

Can you help me with those questions about affinity? Thanks