Custom distribution by pm.DensityDist not coincide with built-in distribution in PyMC4

Questions v5
3

Thank you so much for your quick reply.
Before the 1st post, I tried

def _logp(obs, mu, sigma):
    z = (obs-mu)/sigma
    return -at.sum(z**2) / 2 - at.log(2*np.pi*sigma**2) /2

and had a similarly biased posterior. But I should have included the normalization constant inside the at.sum() … silly mistake.

Now, both

    return at.sum(-z**2 / 2 - at.log(sigma) )

and

    return -z**2 / 2 - at.log(sigma)

work fine. Thank you!