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Bayesian Modeling and Probabilistic Programming in Python
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BUG: <can't running multiple chains in SMC-ABC> #7032

Open Fxinyu opened 1 year ago

Fxinyu commented 1 year ago

Describe the issue:

I have encountered a problem of running multiple chains. I tried the example in Sequential Monte Carlo - Approximate Bayesian Computation. The model could work under only one chain, but when it comes to two or above number of chains, the sampling process cannot proceed further. Screenshot 2023-11-24 100911 Screenshot 2023-11-24 101051

Reproduceable code example:

import arviz as az
import matplotlib.pyplot as plt
import numpy as np
import pymc as pm

print(f"Running on PyMC v{pm.__version__}")
from scipy.integrate import odeint

# Definition of parameters
a = 1.0
b = 0.1
c = 1.5
d = 0.75

# initial population of rabbits and foxes
X0 = [10.0, 5.0]
# size of data
size = 100
# time lapse
time = 15
t = np.linspace(0, time, size)

# Lotka - Volterra equation
def dX_dt(X, t, a, b, c, d):
    """Return the growth rate of fox and rabbit populations."""

    return np.array([a * X[0] - b * X[0] * X[1], -c * X[1] + d * b * X[0] * X[1]])

# simulator function
def competition_model(rng, a, b, size=None):
    return odeint(dX_dt, y0=X0, t=t, rtol=0.01, args=(a, b, c, d))
# function for generating noisy data to be used as observed data.
def add_noise(a, b):
    noise = np.random.normal(size=(size, 2))
    simulated = competition_model(None, a, b) + noise
    return simulated
# plotting observed data.
observed = add_noise(a, b)
_, ax = plt.subplots(figsize=(12, 4))
ax.plot(t, observed[:, 0], "x", label="prey")
ax.plot(t, observed[:, 1], "x", label="predator")
ax.set_xlabel("time")
ax.set_ylabel("population")
ax.set_title("Observed data")
ax.legend();
with pm.Model() as model_lv:
    a = pm.HalfNormal("a", 1.0)
    b = pm.HalfNormal("b", 1.0)

    sim = pm.Simulator("sim", competition_model, params=(a, b), epsilon=10, observed=observed)

    idata_lv = pm.sample_smc(cores =2 ,chains=2)

Error message:

the sampling process cannot proceed further.

PyMC version information:

Running on PyMC v5.9.1

Context for the issue:

No response

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