This directory contains two versions of the BT implementation:

- the standard version that has better cache utilization
- the "blocking" version that contains codes for better vectorization

For most platforms, the standard version gives reasonable performance. 
To access the blocking version, use the VERSION=BLK make flag, such as,
   make CLASS=A VERSION=BLK

Since there is no standard way of performing vectorization, the mileage
you get from the vector version depends very much on compilers.  Often
additional compiler directives (or flags) may be necessary for optimal
results.  The current version is intended to only serve as a baseline.
