Pass user specified directories to the build system

[nonhermitian]

Informations

• Qiskit AER version: 0.1
• Operating system: OSX

What is the current behavior?

The make system does not find the OpenBLAS libraries in their default location in OSX. Instead, the Apple Accelerate libs are always used.

Steps to reproduce the problem

What is the expected behavior?

The installer should find the OpenBLAS libs if they are installed in the default dirs.

Suggested solutions

[atilag]

There's a way to specify the BLAS implementation you want to use for building in CMake. Apple Accelerate is our first candidate, so if CMake finds it, it just uses it.
This is not configurable at the moment.
Seems to be a good candidate for a Good First Issue

[atilag]

Adding HINTS parameter to the find_package() and takeing it's value from a env variable seems the way to go here:

find_package(BLAS HINTS "$ENV{MY_ENV_VARIABLE}" REQUIRED)

[a07r]

@atilag

I'm looking to get started, Not sure what "build system" tag is for! (there isn't a description to it in the labels)

Can I start here with this issue? (It's an old issue, has anything changed since you last made the comment!)

Edit: My Bad! I didn't notice that it's assigned to you already, Please ignore this comment!

[atilag]

We have introduced a way to do this with BLAS so I'm closing this issue.