spin-sim 0.1.4

Ising model Monte Carlo: Metropolis, Gibbs, Wolff, Swendsen-Wang, parallel tempering, Houdayer ICM
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# spin-sim

Pure-Rust Ising model Monte Carlo on periodic hypercubic lattices.

## Algorithms

- Single-spin flips (Metropolis, Gibbs)
- Swendsen-Wang cluster updates
- Wolff single-cluster updates
- Parallel tempering (replica exchange)
- Houdayer isoenergetic cluster move (ICM) for spin glasses

Replicas are parallelized over threads with [rayon](https://crates.io/crates/rayon).

## Usage

```rust
use spin_sim::{Lattice, Realization, run_sweep_loop};

let lattice = Lattice::new(vec![16, 16]);
let temps = vec![2.0, 2.27, 2.5];
let n_replicas = 2;

// Random ±1 couplings (bimodal spin glass)
let couplings: Vec<f32> = (0..lattice.n_spins * lattice.n_neighbors)
    .map(|i| if i % 2 == 0 { 1.0 } else { -1.0 })
    .collect();

let mut real = Realization::new(&lattice, couplings, &temps, n_replicas, 42);

let result = run_sweep_loop(
    &lattice, &mut real,
    n_replicas, temps.len(),
    10_000,   // total sweeps
    1_000,    // warmup sweeps
    "metropolis", // sweep_mode
    None,     // cluster_update_interval
    "wolff",  // cluster_mode (unused when interval is None)
    Some(1),  // pt_interval
    None,     // houdayer_interval
    &|| {},   // on_sweep callback
);

println!("energies: {:?}", result.energies);
```

## Python

For a batteries-included Python interface, see [`peapods`](https://pypi.org/project/peapods/).