Odd nlat discrepancy

I was trying to play around with the odd nlat case and it doesn’t seem to be working as expected. This is a simple script to show the issue.

import math
import numpy as np
import shtns


nlat = 33
nlon = 48

lmax = 7
mmax = 7

sh = shtns.sht(lmax=lmax, mmax=mmax, mres=1, norm=shtns.sht_orthonormal)
sh.set_grid(nlat, nlon,
        flags=shtns.sht_reg_fast | shtns.SHT_PHI_CONTIGUOUS,
        polar_opt=1.0e-10)

theta = np.arccos(sh.cos_theta)
phi = (2.0 * np.pi / nlon) * np.arange(nlon)

n, m = 1, 0
ynm = sh.spec_array()
ynm[sh.idx(n, m)] = np.sqrt(
        4.0 * np.pi / (2 * n + 1)
        * math.factorial(n + m) / math.factorial(n - m))

sht_theta = np.arccos(sh.synth(ynm))
print(f"sht_theta[0, :]: {sht_theta[0, :]}")
print(f"sht_theta[:, 0]: {sht_theta[:, 0]}")
print(f"theta:           {theta}")

print(f"sht_theta {sht_theta.shape} theta {theta.shape}")
print(f"error: ", np.linalg.norm(sht_theta[:, 0] - theta))

Basically, the sht_theta[:, 0] should be the same as theta here (and they are for even nlat), but they’re different sizes.

Am I doing something wrong or is this a bug?

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