Linear algebra error crashes detrender

[amcody]

k2sc runs successfully on most of my light curves, but I am finding that for a percent or two of them, it returns an error in the section of gp.py that calls scipy.linalg.cho_factor.

k2sc/src/gp.py

Lines 83 to 84 in 33eedb9

	self._K = self._K0 + self.kernel._pm[-1]**2 * identity(self._K0.shape[0])
	self._L = sla.cho_factor(self._K)

The particular error message is numpy.linalg.LinAlgError: 943-th leading minor of the array is not positive definite
(though the number 943 changes from light curve to light curve), and it causes a fatal crash. I don't understand why this is happening, as the offending light curves do not have any obvious defects.

[amcody]

Update: I just noticed that the problem must be related to some changes that were implemented in the last year or so, because I'm now getting these crashes where I did not use to. In other words, I successfully ran k2sc on some "AMC format" files last year and output fits files. I am redoing them now because I found that the output cadences were wrong (16 bit vs 32 bit). But when I go to redo them, a small fraction fail and I'm stuck with the old output.

[benjaminpope]

Hi @amcody,

I'm sorry I'm only getting to this now. Do you have an example where it braks? I can try and figure it out.

All the best,

Ben