Metadata-Version: 2.2
Name: cpp_hf
Version: 0.0.0
Summary: Hartree–Fock (k-grid) with FFTW + Eigen via pybind11
Keywords: hartree-fock,fftw,eigen,pybind11,condensed-matter,physics
Author-Email: Tobias Wolf <public@wolft.xyz>
License: GNU GENERAL PUBLIC LICENSE
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Classifier: License :: OSI Approved :: GNU General Public License v2 or later (GPLv2+)
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 3
Classifier: Programming Language :: Python :: 3 :: Only
Classifier: Programming Language :: C++
Classifier: Operating System :: MacOS
Classifier: Operating System :: POSIX :: Linux
Classifier: Topic :: Scientific/Engineering :: Physics
Project-URL: Homepage, https://github.com/skilledwolf/cpp_hf
Project-URL: Issues, https://github.com/skilledwolf/cpp_hf/issues
Requires-Python: >=3.8
Description-Content-Type: text/markdown

# cpp_hf — Fast Hartree–Fock on k‑grids (FFTW + Eigen + pybind11)

[![PyPI](https://img.shields.io/pypi/v/cpp-hf.svg)](https://pypi.org/project/cpp-hf/)
[![Python](https://img.shields.io/pypi/pyversions/cpp-hf.svg)](https://pypi.org/project/cpp-hf/)
[![Wheel](https://img.shields.io/pypi/wheel/cpp-hf.svg)](https://pypi.org/project/cpp-hf/#files)
[![License](https://img.shields.io/pypi/l/cpp-hf.svg)](LICENSE)
[![Release](https://github.com/skilledwolf/cpp_hf/actions/workflows/wheels.yml/badge.svg)](https://github.com/skilledwolf/cpp_hf/actions/workflows/wheels.yml)

cpp_hf provides a compiled extension module exposing a fast Hartree–Fock
self‑consistent field (SCF) loop for uniform 2D k‑grids. It uses
FFTW (batched 2D complex DFTs), Eigen (Hermitian eigendecompositions), and
pybind11 to bind the C++ implementation to Python.

- Batched 2D FFTs (FFTW guru interface)
- Dense Hermitian diagonalization (Eigen)
- EDIIS + Broyden mixing (robust convergence)
- Simple, NumPy‑friendly API

This package is designed to interoperate with ContiMod, but it can be used on
its own as a lightweight HF kernel.

Project links:
- PyPI: https://pypi.org/project/cpp-hf/
- Source: https://github.com/skilledwolf/cpp_hf

## Installation

Quick install (prebuilt wheel if available):
```
pip install cpp-hf
```

Note: the Python import name is `cpp_hf` (underscore).

Advanced installation, source builds, platform tips, and troubleshooting:
see `Installation.md`.

## Quick start

```python
import numpy as np
import cpp_hf

# Grid and shapes
nk = 128; d = 2
weights = np.ones((nk, nk)) * ( (2/nk)*(2/nk) / (2*np.pi)**2 )  # scalar mesh measure
H = np.zeros((nk, nk, d, d), dtype=np.complex128)
Vq = (1.0/np.sqrt((np.linspace(-1,1,nk)[:,None]**2 + np.linspace(-1,1,nk)[None,:]**2) + 0.1)).astype(np.complex128)[...,None,None]
P0 = np.zeros_like(H)

# Target electron density (half‑filling)
ne_target = 0.5 * d * weights.sum()

P_fin, F_fin, E_fin, mu_fin, n_iter = cpp_hf.hartreefock_iteration_cpp(
    weights, H, Vq, P0,
    float(ne_target),  # electron density target
    0.5,               # temperature
    50,                # max_iter
    1e-3,              # commutator tolerance
    6,                 # mixing history (DIIS/EDIIS/Broyden)
    1.0,               # mixing alpha (kept for compatibility)
)
print("iters:", n_iter, "mu:", mu_fin, "E:", E_fin)
```

## API

```python
hartreefock_iteration_cpp(
    weights:      np.ndarray[(nk,nk), float64],
    hamiltonian:  np.ndarray[(nk,nk,d,d), complex128],
    v_coulomb:    np.ndarray[(nk,nk,1,1) or (nk,nk,d,d), complex128],
    p0:           np.ndarray[(nk,nk,d,d), complex128],
    electron_density0: float,
    T: float,
    max_iter: int,
    comm_tol: float,
    diis_size: int,
    mixing_alpha: float,
) -> tuple[P, F, E, mu, n_iter]
```

- `weights` is the uniform k‑mesh measure (e.g., `dkx*dky/(2π)^2`).
- `v_coulomb` can be scalar per‑k (`[...,1,1]`) or a full matrix per‑k (`[...,d,d]`).
- Returns the converged density `P`, mean‑field `F`, total energy, chemical
  potential, and the iteration count.

## License

GPLv2+ — see `LICENSE`.

Third‑party notices: see `THIRD_PARTY_NOTICES.md`.

## Acknowledgments

- FFTW — GPLv2+ (www.fftw.org)
- Eigen — MPL2
- pybind11 — BSD‑style
