I was looking into BLAS.scala routines for MLlib’s vectors and matrices. It looks like Spark uses the F2jblas for level 1 routines.

https://github.com/apache/spark/blob/master/mllib-local/src/main/scala/org/apache/spark/ml/linalg/BLAS.scala

// For level-1 routines, we use Java implementation.
private def f2jBLAS: NetlibBLAS = {
  if (_f2jBLAS == null) {
    _f2jBLAS = new F2jBLAS
  }
  _f2jBLAS
}

Here are some great resources about different BLAS implementations
http://www.spark.tc/blas-libraries-in-mllib/

https://blog.cloudera.com/blog/2017/02/accelerating-apache-spark-mllib-with-intel-math-kernel-library-intel-mkl/

BLAS routines (Level 1,2,3)
http://www.netlib.org/blas/#_blas_routines