Changing the BLAS from openblas on a F32 box

Thanks (again) I?aki.

There was a typo in my reply above. I should have said: I *can't*
answer the question re USE_LOCKING=1.

:)

Those other suggestions are really helpful too; I really didn't
understand what the difference was (I'm still not clear what the
differences are between say openblas-openmp and openblas-openmp64),
but I did get R to pass mgcv's thread safe test with both
openblas-openmp and blis-openmp, so I have aliased those options for
use too.

Basically, openblas has a number of features that can be enabled or
disabled: 64-bit integer support, threading and parallelization of
certain parts using openmp (as, e.g., data.table does). With the
combination of these features, we end up with many different flavors,
and all these are compiled and sub-packaged separately.

Usually, you want parallelization at the top level calling a serial
version, as mgcv does. Otherwise, you may end up with an "explosion"
of threads that is counterproductive.

I?aki ?car