Package fails in docker container. Reinstall and it works. Why?

Question

I am running a docker container that works perfectly on multiple different hosts. However when I run on AWS cr1.8xlarge one of the packages (bcolz) fails with "invalid instruction" error.

I exec into the container and run bcolz.test() which fails. But if I pip uninstall bcolz and then reinstall the same version with pip install bcolz==1.1.1 and run bcolz.test() again and it works.

How can this be?

Answer 1

The setup.py compiles bcolz with different flags depending on the CPU. This means bcolz is not portable in a docker container.