Nutpie Documentation

nutpie is a high-performance library designed for Bayesian inference, that provides efficient sampling algorithms for probabilistic models. It can sample models that are defined in PyMC or Stan (numpyro and custom hand-coded likelihoods with gradient are coming soon).

Faster sampling than either the PyMC or Stan default samplers. (An average ~2x speedup on posteriordb compared to Stan)
All the diagnostic information of PyMC and Stan and some more.
GPU support for PyMC models through jax.
A more informative progress bar.
Access to the incomplete trace during sampling.
Experimental normalizing flow adaptation for more efficient sampling of difficult posteriors.

Quickstart: PyMC

Install nutpie with pip, uv, pixi, or conda:

For usage with pymc:

# One of
pip install "nutpie[pymc]"
uv add "nutpie[pymc]"
pixi add nutpie pymc numba
conda install -c conda-forge nutpie pymc numba

And then sample with

import nutpie
import pymc as pm

with pm.Model() as model:
    mu = pm.Normal("mu", mu=0, sigma=1)
    obs = pm.Normal("obs", mu=mu, sigma=1, observed=[1, 2, 3])

compiled = nutpie.compile_pymc_model(model)
trace = nutpie.sample(compiled)

Sampler Progress

Total Chains: 6

Active Chains: 0

Finished Chains: 6

Sampling for now

Estimated Time to Completion: now

Draws	Step Size	Gradients/Draw
1400	1.35	1
1400	1.28	3
1400	1.29	3
1400	1.23	3
1400	1.40	3
1400	1.28	1

For more information, see the detailed PyMC usage guide.

Quickstart: Stan

Stan needs access to a compiler toolchain, you can find instructions for those here. You can then install nutpie through pip or uv:

# One of
pip install "nutpie[stan]"
uv add "nutpie[stan]"

import nutpie

model = """
data {
    int<lower=0> N;
    vector[N] y;
}
parameters {
    real mu;
}
model {
    mu ~ normal(0, 1);
    y ~ normal(mu, 1);
}
"""

compiled = (
    nutpie
    .compile_stan_model(code=model)
    .with_data(N=3, y=[1, 2, 3])
)
trace = nutpie.sample(compiled)