Does NNPACK fall back to non-accelerated code when "Could not initialize NNPACK! Reason: Unsupported hardware." occurs?

[KoenT-SS]

Hi,

first: context:
I inherited a project using Python3 and PyTorch 1.11.0, and I was running this on Ubuntu 20.04 on an (old) desktop machine.
When I run the code, I'm seeing this message pop up (it doesn't say if it's an error or a warning):
[W NNPACK.cpp:51] Could not initialize NNPACK! Reason: Unsupported hardware.
I checked /proc/cpuinfo and the machine doesn't support AVX2 (it's an Intel(R) Core(TM)2 Quad CPU Q8200 @ 2.33GHz), so that could be the reason for this message.
The code does appear to continue to run though, and I also get a nice confusion matrix of the classification task it's running at the end, which appears reasonable compared to previously reported results with that code.

So, my question is:
What happens when NNPACK detects there is no AVX2 support (I presume) on the machine it's running on?
Does it fall back to non-accelerated code in that case (so, still running correctly, but slower)?

Thanks for your feedback!

Koen

[Marat Dukhan]

NNPACK doesn't have a fall-back for unsupported machines. Higher-level frameworks integrating NNPACK may have one.