r-values not returned in Python histograms() call.

[tcnicholas]

I am using the Python wrapper below to compute the histograms for sets of coordinates. The resultant array h is of the expected shape (1293, 4), however the first column is filled with zeros, rather than the expected r-values from the histogramming. Perhaps I am missing something obvious?

I am running cadishi version 1.1.4, with Python 3.9.7 [Clang 10.0.0 ], on macOS Monterey v12.0.1.

from cadishi.kernel.pydh import histograms
import numpy as np

# define periodic box.
box = np.array([60.4344, 62.7234, 51.7356])

# define number of bins and rmax.
bin_width = 0.02
rmax = 0.5 * box.min()
nbins = int(rmax // bin_width)

# gather together np.ndarrays of coordinates for Ca and O atoms.
coordinate_sets = [ca_pos, o_pos]

# compute histograms
h = histograms(coordinate_sets, rmax, nbins, box=box)

# remove self-distances.
h[0,:].fill(0)

print(h.shape)
print(h)

returns:

                       pydh box_type: orthorhombic
(1293, 4)

[[    0     0     0     0]
 [    0     0     0     0]
 [    0     0     0     0]
 ...
 [    0  2481 19511 40129]
 [    0  2467 19835 40162]
 [    0  2477 19647 40435]]