AttributeError: 'Scratchpad' object has no attribute 'ufunc'

Questions v5
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Hi Jesse,

Thank you so much for your advice. I learned about pytensor.scan and the “boilerplate” code you provided in Declaring Priors using Loops for State Space Models - #2 by jessegrabowski, and they solved my problem.

Revised code which worked without error:

import numpy as np
import pymc as pm
from pymc.pytensorf import collect_default_updates
import pytensor
import pytensor.tensor as pt

N = 32
Y = np.random.randint(0, 20, size=N)

# Helper function for pm.CustomDist
n_steps = N - 1
def statespace_dist(mu_init, sigma_level, size):

    def grw_step(mu_tm1, sigma_level):
        mu_t = mu_tm1 + pm.Normal.dist(sigma=sigma_level)
        return mu_t, collect_default_updates(outputs=[mu_t])

    mu, updates = pytensor.scan(fn=grw_step, 
                                outputs_info=[{"initial": mu_init}],
                                non_sequences=[sigma_level], 
                                n_steps=n_steps,
                                name='statespace',
                                strict=True)

    return mu

with pm.Model() as model:
    alpha1 = pm.Uniform('alpha[1]', 0, 10)
    sigma = pm.Uniform('sigma', 0, 100)

    alpha = pm.CustomDist('alpha', alpha1, sigma, dist=statespace_dist)
    alpha = pt.concatenate([[alpha1], alpha])

    l = pm.Deterministic('lambda', alpha.exp())
    Yobs = pm.Poisson('Y', mu=l, observed=Y)

with model:
    trace = pm.sample(1000, progressbar=False)
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