racah 0.2.0

Racah-Wigner calculus for compact Lie groups: exact SU(2) recoupling, and runtime Clebsch-Gordan / F- / R-coefficient generation for SU(N), SO(N), and Sp(2N)
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//! Base-only one-shot coefficient-cache budget contract.

use racah::cache::{
    base_cache_stats, cache_budgets, configure_cache_budgets, reset, CacheBudgetError,
    CoefficientCacheBudgets, CoefficientCacheTier,
};
use racah::wigner_6j;

#[test]
fn zero_budget_is_retryable_then_compute_without_retention() {
    let invalid =
        CoefficientCacheBudgets::default().with_limit(CoefficientCacheTier::ThreeJ, usize::MAX);
    assert!(matches!(
        configure_cache_budgets(invalid),
        Err(CacheBudgetError::ExceedsMaximum {
            tier: CoefficientCacheTier::ThreeJ,
            ..
        })
    ));

    let budgets = CoefficientCacheBudgets::disabled();
    configure_cache_budgets(budgets).unwrap();
    assert_eq!(cache_budgets(), budgets);
    let value = wigner_6j(2, 2, 2, 2, 2, 2);
    assert!((value.to_f64() - 1.0 / 6.0).abs() < 1e-14);
    let stats = base_cache_stats();
    assert_eq!(stats.six_j.entries, 0);
    assert_eq!(stats.six_j.bytes, 0);
    assert_eq!(stats.six_j.evictions, 1);
    reset();
    assert_eq!(cache_budgets(), budgets, "reset must preserve the policy");
    assert_eq!(
        configure_cache_budgets(CoefficientCacheBudgets::default()),
        Err(CacheBudgetError::AlreadyInitialized)
    );
}