[mlpack-git] [mlpack] hmm_train failed to converge (#496)

[Ryan Curtin]

Just a quick update: I've been looking into this, and I found a random seed that allows me to reproduce the issue, but when I use a debugger to step through the calculations to find out where the NaN is coming from, the results don't make any sense.  If I print the value with cout, it gives me something different than what I get if I don't print it and use gdb to inspect.  I'm digging deeper, but I don't have anything yet...

It does appear that this occurs because the covariance matrices for individual Gaussians are getting very small.  I think with your dataset this happens in part because there are so many points with the exact same values.  I know this isn't a solution, but I suspect that if you were to add noise to each point (maybe Gaussian noise with standard deviation 1e-15 or something else quite small), you might encounter fewer or no crashes like this.

I'll keep looking and let you know when I get to the bottom of this. :)

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Reply to this email directly or view it on GitHub:
https://github.com/mlpack/mlpack/issues/496#issuecomment-172860010
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