pub fn evaluate(&self, r: Vec<FieldElement<F>>) -> Result<FieldElement<F>, MultilinearError> {
        if r.len() != self.num_vars() {
            return Err(MultilinearError::IncorrectNumberofEvaluationPoints(
                r.len(),
                self.num_vars(),
            ));
        }
        let mut chis: Vec<FieldElement<F>> =
            vec![FieldElement::one(); (2usize).pow(r.len() as u32)];
        let mut size = 1;
        for j in r {
            size *= 2;
            for i in (0..size).rev().step_by(2) {
                let half_i = i / 2;
                let temp = &chis[half_i] * &j;
                chis[i] = temp;
                chis[i - 1] = &chis[half_i] - &chis[i];
            }
        }
        #[cfg(feature = "parallel")]
        let iter = (0..chis.len()).into_par_iter();
        #[cfg(not(feature = "parallel"))]
        let iter = 0..chis.len();
        Ok(iter.map(|i| &self.evals[i] * &chis[i]).sum())
    }
Evaluates `self` at the point `r` (a vector of FieldElements) in O(n) time.
`r` must have a value for each variable.
crates/math/src/polynomial/dense_multilinear_poly.rs