apache/spark — pull request #3462 by dbtsai (2014-11-26 01:06:02+00:00)
Title: Implement the efficient vector norm

The vector norm in breeze is implemented by `activeIterator` which is known to be very slow.
In this PR, an efficient vector norm is implemented, and with this API, `Normalizer` has huge
performance gain.

Here is the benchmark against mnist8m dataset.

Before
DenseVector: 68.25secs
SparseVector: 17.01secs

With this PR
DenseVector: 12.71secs
SparseVector: 2.73secs