### What changes were proposed in this pull request?
This patch introduces a VectorizedBLAS class which implements such hardware-accelerated BLAS operations. This feature is hidden behind the "vectorized" profile that you can enable by passing "-Pvectorized" to sbt or maven.
The Vector API has been introduced in JDK 16. Following discussion on the mailing list, this API is introduced transparently and needs to be enabled explicitely.
### Why are the changes needed?
Whenever a native BLAS implementation isn't available on the system, Spark automatically falls back onto a Java implementation. With the recent release of the Vector API in the OpenJDK [1], we can use hardware acceleration for such operations.
This change was also discussed on the mailing list. [2]
### Does this PR introduce _any_ user-facing change?
It introduces a build-time profile called `vectorized`. You can pass it to sbt and mvn with `-Pvectorized`. There is no change to the end-user of Spark and it should only impact Spark developpers. It is also disabled by default.
### How was this patch tested?
It passes `build/sbt mllib-local/test` with and without `-Pvectorized` with JDK 16. This patch also introduces benchmarks for BLAS.
The benchmark results are as follows:
```
[info] daxpy: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 37 37 0 271.5 3.7 1.0X
[info] vector 24 25 4 416.1 2.4 1.5X
[info]
[info] ddot: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 70 70 0 143.2 7.0 1.0X
[info] vector 35 35 2 288.7 3.5 2.0X
[info]
[info] sdot: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 50 51 1 199.8 5.0 1.0X
[info] vector 15 15 0 648.7 1.5 3.2X
[info]
[info] dscal: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 34 34 0 295.6 3.4 1.0X
[info] vector 19 19 0 531.2 1.9 1.8X
[info]
[info] sscal: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 25 25 1 399.0 2.5 1.0X
[info] vector 8 9 1 1177.3 0.8 3.0X
[info]
[info] dgemv[N]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 27 27 0 0.0 26651.5 1.0X
[info] vector 21 21 0 0.0 20646.3 1.3X
[info]
[info] dgemv[T]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 36 36 0 0.0 35501.4 1.0X
[info] vector 22 22 0 0.0 21930.3 1.6X
[info]
[info] sgemv[N]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 20 20 0 0.0 20283.3 1.0X
[info] vector 9 9 0 0.1 8657.7 2.3X
[info]
[info] sgemv[T]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 30 30 0 0.0 29845.8 1.0X
[info] vector 10 10 1 0.1 9695.4 3.1X
[info]
[info] dgemm[N,N]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 182 182 0 0.5 1820.0 1.0X
[info] vector 160 160 1 0.6 1597.6 1.1X
[info]
[info] dgemm[N,T]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 211 211 1 0.5 2106.2 1.0X
[info] vector 156 157 0 0.6 1564.4 1.3X
[info]
[info] dgemm[T,N]: Best Time(ms) Avg Time(ms) Stdev(ms) Rate(M/s) Per Row(ns) Relative
[info] ------------------------------------------------------------------------------------------------------------------------
[info] f2j 276 276 0 0.4 2757.8 1.0X
[info] vector 137 137 0 0.7 1365.1 2.0X
```
/cc srowen xkrogen
[1] https://openjdk.java.net/jeps/338
[2] https://mail-archives.apache.org/mod_mbox/spark-dev/202012.mbox/%3cDM5PR2101MB11106162BB3AF32AD29C6C79B0C69DM5PR2101MB1110.namprd21.prod.outlook.com%3eCloses#30810 from luhenry/master.
Lead-authored-by: Ludovic Henry <luhenry@microsoft.com>
Co-authored-by: Ludovic Henry <git@ludovic.dev>
Signed-off-by: Sean Owen <srowen@gmail.com>
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