Bug in qinfer.utils.in_ellipsoid ?

[sapristi]

Hello,
I've been playing with QInfer for it's minimum volume enclosing_ellipse algorithm. It seems there is some bug with the in_ellipsoid function, for which no point used to compute the ellispoid are inside it.

Here's a snippet with the data I used. I have no idea whether it makes sense, but using A instead of it's inverse in the distance computation seem to give a better fit distance (although some points would still be outside of the ellispe).

import numpy as np
import qinfer

# 7 points in 8 dimensions
points = np.array([[9.61671088e+01, 3.09532270e+00, 3.59059099e+00, 3.52696730e+00,
        4.68305129e+00, 4.92967759e+01, 1.52589430e+00, 1.77004559e+00],
       [1.73990050e+02, 2.98332674e+00, 4.39375052e+00, 2.91588476e+00,
        4.07209379e+00, 3.55407545e+01, 1.06029683e+00, 1.56157208e+00],
       [2.37193968e+02, 9.17352808e-01, 1.35086160e+00, 7.16079767e-01,
        1.02764937e+00, 2.94583624e+01, 2.70237115e-01, 3.97941707e-01],
       [1.47826437e+02, 1.08761428e+00, 1.75354413e+00, 1.32319382e+00,
        2.81922693e+00, 3.98934693e+01, 4.33887070e-01, 6.99549591e-01],
       [6.32894555e+02, 2.45578343e+00, 3.75805515e+00, 8.68867797e+00,
        1.14160928e+01, 1.35298152e+01, 3.32262960e-01, 5.08457917e-01],
       [2.01686471e+02, 1.55523380e+00, 1.76140513e+00, 1.37662800e+00,
        1.55630744e+00, 3.27865510e+01, 5.09907521e-01, 5.77503991e-01],
       [1.86267513e+02, 2.65450049e+00, 3.72240851e+00, 3.18004405e+00,
        5.36798721e+00, 3.41711622e+01, 9.07073667e-01, 1.27199025e+00]])
A, c = qinfer.utils.mvee(points, 0.001)
print("in_ellipsoid?", [qinfer.utils.in_ellipsoid(p, A, c) for p in points])
print("distance", [
    np.einsum('j,jl,l', c-p, np.linalg.inv(A), c-p)
    for p in points
])
print("distance fixed?", [
    np.einsum('j,jl,l', c-p, A, c-p)
    for p in points
])

Output:

in_ellipsoid? [False, False, False, False, False, False, False]
distance [13612175772.118567, 5243680294.202738, 1343921122.9179094, 7623619437.438548, 34964549033.975334, 3221636117.3242393, 4282303012.8117304]
distance fixed? [1.140625, 0.6796875, 0.71484375, 1.26025390625, 0.3359375, 0.94921875, 0.931640625]