We said it before, but it bears repeating: BLAS is an interface.
So unless you use on a static library build, these library can be switch
after compilation and at essentially any point in time. My (unfinished)
package gcbd shows how in its simple and vignette by comparing a number of
BLAS implementations. See the (now dated) chart on page 9 of
https://cran.rstudio.com/web/packages/gcbd/vignettes/gcbd.pdf
or this (old) blog post
http://dirk.eddelbuettel.com/blog/2010/10/03/
While the charts could do with an update, they do show how eg reference blas
is clearly outperformed by Atlas or GotoBLAS (the predecessor to OpebBLAS).
Hope this helps, Dirk