[zero3] apex was installed without --cpp_ext. Falling back to Python flatten and unflatten.

[stas00]

Running on one setup the current master I get:

[2021-03-18 22:12:42,472] [WARNING] [stage3.py:34:<module>] apex was installed without --cpp_ext.  
Falling back to Python flatten and unflatten.

Is it using a previously installed apex, or an apex comes with DeepSpeed and what needs to be done to make it fast?

I don't see apex already installed on that setup. And I'm not using it in the ds config file.

Thank you.

[stas00]

It's because try doesn't check if apex is even installed before checking for apex_C. So it needs to be fixed.

However we are discussing removing this code altogether at #910 (comment) which would close this issue.