Chu-Rong Chen

### Bug Description I'm recently trying to obtain the gradient of model state w.r.t. model parameter, for example, the gradient of `joint_q` w.r.t. `body_mass`. The derivation of gradient works, but...

I'm currently debugging the gradient flow of `FeatherstoneIntegrator` so I wrote the following code: ```python import math import os from typing import Optional import numpy as np import warp as...