unxt

Unitful Quantities in JAX

Unxt is unitful quantities and calculations in JAX, built on Equinox and Quax.

Yes, it supports auto-differentiation (grad, jacobian, hessian) and vectorization (vmap, etc).

Installation

pip install unxt

Documentation

Quick example

from unxt import Quantity

x = Quantity(jnp.arange(1, 5, dtype=float), "kpc")
print(x)
# Quantity['length'](Array([1., 2., 3., 4.], dtype=float64), unit='kpc')

# Addition / Subtraction
print(x + x)
# Quantity['length'](Array([2., 4., 6., 8.], dtype=float64), unit='kpc')

# Multiplication / Division
print(2 * x)
# Quantity['length'](Array([2., 4., 6., 8.], dtype=float64), unit='kpc')

y = Quantity(jnp.arange(4, 8, dtype=float), "Gyr")

print(x / y)
# Quantity['speed'](Array([0.25      , 0.4       , 0.5       , 0.57142857], dtype=float64), unit='kpc / Gyr')

# Exponentiation
print(x**2)
# Quantity['area'](Array([0., 1., 4., 9.], dtype=float64), unit='kpc2')

# Unit Checking on operations
try:
    x + y
except Exception as e:
    print(e)
# 'Gyr' (time) and 'kpc' (length) are not convertible

unxt is built on quax, which enables custom array-ish objects in JAX. For convenience we use the quaxed library, which is just a quax.quaxify wrapper around jax to avoid boilerplate code.

from quaxed import grad, vmap
import quaxed.numpy as jnp

print(jnp.square(x))
# Quantity['area'](Array([ 1.,  4.,  9., 16.], dtype=float64), unit='kpc2')

print(qnp.power(x, 3))
# Quantity['volume'](Array([ 1.,  8., 27., 64.], dtype=float64), unit='kpc3')

print(vmap(grad(lambda x: x**3))(x))
# Quantity['area'](Array([ 3., 12., 27., 48.], dtype=float64), unit='kpc2')

Since Quantity is parametric, it can do runtime dimension checking!

LengthQuantity = Quantity["length"]
print(LengthQuantity(2, "km"))
# Quantity['length'](Array(2, dtype=int64, weak_type=True), unit='km')

try:
    LengthQuantity(2, "s")
except ValueError as e:
    print(e)
# Physical type mismatch.

Citation

If you found this library to be useful and want to support the development and maintenance of lower-level code libraries for the scientific community, please consider citing this work.

Development

We welcome contributions!