IndexOutOfBoundsException in RandomSeedGenerator.buildRandom()

[Shannon Quinn]

Hi all,

Thanks once more for everyone's help so far, it's been extremely 
fruitful. I'm about 98% of the way finished with my first sprint, but 
unfortunately there is a single error on my second-to-last line of code.

Right after performing an eigen-decomposition using the 
DistributedLanczosSolver, I feed the outputs directly into the KMeans 
utility, RandomSeedGenerator, in order to create random cluster 
centroids for a given K. Unfortunately, during that buildRandom() method 
call, I hit an index out of bounds exception, and it seems to be an 
off-by-1 problem (for k=3, the arrays generated are only of length 2).

More detail to be found here: 
http://spectrallyclustered.wordpress.com/2010/06/18/sprint-1-so-very-close/

I think part of the problem is due to a lack of understanding of the 
LanczosSolver process. I do know that the eigenvectors are returned as 
rows in a matrix, in which case the data points I need to feed to KMeans 
are the columns. How does the desiredRank parameter fit in when it's 
returning a row matrix? The rule of thumb I'm using is that # of 
clusters = # of eigenvectors, is there any way to enforce this heuristic 
explicitly?

Any insights here would be greatly appreciated; I've posted a patch with 
my latest code on JIRA. Thanks so much!

Regards,
Shannon