Github user mengxr commented on the pull request:

    https://github.com/apache/spark/pull/11610#issuecomment-197557069
  
    @dbtsai There is a good chance of precision loss during the computation of 
A^T A is A is ill-conditioned. A better approach is to factorize A directly. It 
is similar to tall-skinny QR without storing Q (applying Q^T to be directly). 
SVD is similar. See this paper: 
http://web.stanford.edu/~paulcon/docs/mapreduce-2013-arbenson.pdf. We can 
definitely switch to it to get better stability but we need to handle sparsity, 
which might not be worth the time.
    
    @iyounus You can use `RCOND` to control the rank estimation. Usually a 
number like `1e-12` should work well.


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