First Order Model-Based RL through Decoupled Backpropagation (DMO) — Code

This repository accompanies the paper “First Order Model-Based RL through Decoupled Backpropagation,” which proposes Decoupled forward–backward Model-based policy Optimization (DMO): unroll trajectories in a high‑fidelity simulator while computing gradients via a learned differentiable model to enable efficient first‑order optimization without simulator derivatives.

Project links

• Website: https://machines-in-motion.github.io/DMO/
• Paper (arXiv): https://arxiv.org/abs/2509.00215v1
• Announcement (X/Twitter): https://x.com/Jsphamigo/status/1964347428221415450

Status

• Supported now: DMO‑SHAC on DFlex environments (training script and configs included) and on IsaacGym Go2 quadrupedal walking env.
• Coming soon: DMO‑SHAC on IsaacGym for bipedal walking env; DMO‑SAPO on DFlex, IsaacGym, and reawarped; active work‑in‑progress repository.

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Installation

DFlex environments

conda env create -f diffrl_conda.yml
conda activate dmo_dflex

cd dflex
pip install -e .

The commands above create and activate the DMO environment for DFlex and install the local DFlex package in editable mode for development workflows.

IsaacGym environments

Git clone our fork of IsaacGymEnvs:

git clone https://github.com/Jogima-cyber/IsaacGymEnvs.git

Download Isaac Gym: https://developer.nvidia.com/isaac-gym and run the following commands:

conda create -n IsaacGymEnvs python=3.8
conda activate IsaacGymEnvs

conda install pip
conda install -c conda-forge ninja

# Download Isaac Gym: https://developer.nvidia.com/isaac-gym 
cd path/to/isaacgym/python && pip install --no-cache-dir -e . 

# Install our fork of IsaacGymEnvs that you previously cloned
cd path/to/IsaacGymEnvs/ && pip install --no-cache-dir  -e .

pip uninstall torch tochvision
pip install --no-cache-dir torch==2.2.0 torchvision==0.17.0
# Fix compability problem with numpy version
pip install --no-cache-dir "numpy<1.24"
pip install --no-cache-dir texttable av

# Add correct LD_LIBRARY_PATH on env start
conda env config vars set LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$CONDA_PREFIX/lib --name $CONDA_DEFAULT_ENV

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Quick start

Train: DMO‑SHAC on DFlex

conda activate dmo_dflex
cd examples
python train_dmo_shac.py \
  --exp_name dmo_shac \
  --logdir ./logs/Ant/dmo_shac/20 \
  --cfg ./cfg/dmo_shac/ant.yaml \
  --seed 20

This launches DMO‑SHAC on Ant using the provided config, logging to the specified directory with a fixed seed for reproducibility.

Train: DMO‑SHAC on IsaacGym Go2 Quadrupedal Walking Env

conda activate IsaacGymEnvs
python train_dmo_shac.py \
  --exp_name dmo_shac \
  --logdir ./logs/Go2/dmo_shac/20 \
  --cfg ./cfg/dmo_shac/go2.yaml \
  --seed 20 \
  --env_type isaac_gym
cd examples

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Configuration and logging

• Configs for DMO‑SHAC are under examples/cfg/dmo_shac and include task, optimizer, and logging settings.
• To disable Weights & Biases, set wandb_track: False in the config files in examples/cfg/dmo_shac; local logs still go under --logdir.
• Seeding is controlled via the --seed flag to facilitate reproducible experiments.

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Roadmap (WIP)

• Add cleaned scripts for DMO‑SHAC training on IsaacGym for bipedal walking.
• Add cleaned scripts for DMO‑SAPO implementations on DFlex, IsaacGym, and reawarped.

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Citation

If this code or paper is useful, please cite the work below.

@inproceedings{amigo2025dmo,
  title     = {First Order Model-Based RL through Decoupled Backpropagation},
  author    = {Amigo, Joseph and Khorrambakht, Rooholla and Chane-Sane, Elliot and Mansard, Nicolas and Righetti, Ludovic},
  booktitle = {Conference on Robot Learning (CoRL)},
  year      = {2025},
  note      = {arXiv:2509.00215}
}

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