Function watts_strogatz_game 

pub fn watts_strogatz_game(
    size: u32,
    nei: u32,
    p: f64,
    loops: bool,
    multiple: bool,
    seed: u64,
) -> IgraphResult<Graph>

Generate a 1-D Watts–Strogatz small-world graph.

Builds a periodic ring lattice of size vertices where every vertex connects to its nei nearest neighbours on each side (total degree 2·nei), then independently rewires each endpoint of each edge with probability p. The candidate replacement is uniformly sampled from the vertex set, optionally subject to a no-self-loop / no-multi-edge rejection rule.

loops = false rejects any candidate equal to the kept endpoint, multiple = false additionally rejects candidates that would duplicate an existing edge. Both default to false in the canonical Watts–Strogatz Nature ’98 model and in python-igraph’s Graph.Watts_Strogatz. The output is always undirected.

Errors

Returns IgraphError::InvalidArgument if:

• size == 0, or
• 2·nei + 1 > size (the ring would self-overlap), or
• p is NaN, infinite, or outside [0, 1].

Examples

use rust_igraph::watts_strogatz_game;
let g = watts_strogatz_game(10, 2, 0.0, false, false, 42).unwrap();
assert_eq!(g.vcount(), 10);
// p = 0 leaves the lattice untouched: 10 vertices × 2 neighbours
// per side / 2 (undirected) × 2 sides = 20 edges.
assert_eq!(g.ecount(), 20);