about performance statistics of PCA.dml

[Janardhan Pulivarthi]

Hi Mike,

I'd like to know how much expensive this critical code is

 C = (t(A) %*% A)/(N-1) - (N/(N-1))*t(mu) %*% mu;

(at
https://github.com/apache/systemml/blob/master/scripts/algorithms/PCA.dml#L81)
in the SPARK setting given

   1. 60Kx700 input for A
   2. For a datasize of 28 MB with 100 continuous variable and 1 column
   with numeric label variable

with reference to this comment.(
https://issues.apache.org/jira/browse/SYSTEMML-831?focusedCommentId=15525147&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15525147
)

Thank you,
Janardhan