GANSU2

GANSU2 (GPU Accelerated Numerical Simulation Utility) is a GPU-native quantum chemistry package: Hartree-Fock, Kohn-Sham DFT, post-HF (MP2, CCSD, CCSD(T), DLPNO-CCSD, DMET, FCI), excited states (CIS, ADC(2), EOM-CCSD, STEOM-CCSD), analytic gradients / Hessians and geometry optimization, all in double precision on NVIDIA GPUs. It is distributed as a small pip wheel plus a licensed shared library that is fetched on first use.

Full documentation: https://gansu2.github.io/

Install

pip install gansu2

No CUDA toolkit, no compiler, no cmake on your side. The wheel is a thin Python wrapper; the CUDA 12 runtime libraries come in as pip dependencies (nvidia-cublas-cu12, nvidia-cusolver-cu12, ...). On first use GANSU2 downloads the GPU shared library libgansu2.so and the gansu2 command-line tool from the matching release, verifies them against their published SHA-256, and caches them under ~/.cache/gansu2/<version>/.

Requirements

• Linux x86_64 (manylinux_2_28: Ubuntu 20.04+, Debian 10+, RHEL 8+ and equivalents)
• Python 3.8+
• NVIDIA driver compatible with the CUDA 12.x runtime (>= 525.60.13)
• NVIDIA GPU with Compute Capability 8.0+ (Ampere / Ada / Hopper / Blackwell)

Quick test

import gansu2

gansu2.init()
m = gansu2.Molecule("H2O.xyz", basis="sto-3g")
print(f"RHF energy: {m.run(method='RHF').total_energy:.6f} Ha")
gansu2.finalize()

Or from the command line (the gansu2 command is installed by the wheel):

gansu2 -x H2O.xyz -g sto-3g                                   # RHF
gansu2 -x H2O.xyz -g cc-pvdz --post_hf_method ccsd            # CCSD
gansu2 -x H2O.xyz -g cc-pvdz --method rks --functional pbe    # DFT (RKS / PBE)
gansu2 -x H2O.xyz -g cc-pvdz -r optimize                      # geometry optimization
gansu2 --list-basis                                           # bundled basis sets

License key

Small calculations run without any license. Larger ones need a free license key, which grants full, unlimited use (commercial use included):

1. gansu2-license -s prints an 8-character sign-up code.
2. Create an account at the User Portal, enter the sign-up code, and press Start. Your key is emailed to you.
3. gansu2-license -k <YOUR-KEY> -a registers the key on the machine.

The key is a floating license: it is not tied to a machine. See the installation guide and the Terms and Conditions.

Offline / air-gapped use

Download the wheel and the matching libgansu2.so from the release page on a connected machine, then on the target machine:

pip install ./gansu2-<version>-py3-none-manylinux_2_28_x86_64.whl
export GANSU2_LIB=/path/to/libgansu2-<version>-linux-x86_64.so
python -c "import gansu2; gansu2.init()"

GANSU2_LIB makes the loader use that file instead of downloading.

Documentation

• Installation
• CLI guide
• Python API guide
• C API reference
• All parameters

Acknowledgements and license

GANSU2 is developed by Hiroshima University and Fujitsu Limited. It is derived from the open-source GANSU project (BSD-3-Clause, https://github.com/Yasuaki-Ito/GANSU); the BSD-3-Clause notice of GANSU and the third-party components are listed in the NOTICE file shipped with the wheel. The GANSU2 binaries themselves are not BSD-licensed: their use is governed by the Terms and Conditions, shipped as the wheel's LICENSE file.