Function batch_variance_f64 

pub fn batch_variance_f64(values: &[f64]) -> f64

SIMD-friendly variance calculation (population variance).

Uses two-pass algorithm: first calculates mean, then variance. Returns 0.0 for empty or single-element slices.

Example

use presentar_core::simd::batch_variance_f64;
let values = vec![2.0, 4.0, 4.0, 4.0, 5.0, 5.0, 7.0, 9.0];
let variance = batch_variance_f64(&values);
assert!((variance - 4.0).abs() < 0.001);