fn get_periodic_column_polys()

in air/src/air/mod.rs [207:241]

• 30 lines of code
• 2 McCabe index (conditional complexity)

    fn get_periodic_column_polys(&self) -> Vec<Vec<Self::BaseField>> {
        // cache inverse twiddles for each cycle length so that we don't have to re-build them
        // for columns with identical cycle lengths
        let mut twiddle_map = BTreeMap::new();
        // iterate over all periodic columns and convert column values into polynomials
        self.get_periodic_column_values()
            .into_iter()
            .map(|mut column| {
                let cycle_length = column.len();
                assert!(
                    cycle_length >= MIN_CYCLE_LENGTH,
                    "number of values in a periodic column must be at least {}, but was {}",
                    MIN_CYCLE_LENGTH,
                    cycle_length
                );
                assert!(
                    cycle_length.is_power_of_two(),
                    "number of values in a periodic column must be a power of two, but was {}",
                    cycle_length
                );
                assert!(cycle_length <= self.trace_length(),
                    "number of values in a periodic column cannot exceed trace length {}, but was {}",
                    self.trace_length(),
                    cycle_length
                );

                // get twiddles for interpolation and interpolate values into a polynomial
                let inv_twiddles = twiddle_map
                    .entry(cycle_length)
                    .or_insert_with(|| fft::get_inv_twiddles::<Self::BaseField>(cycle_length));
                fft::interpolate_poly(&mut column, inv_twiddles);
                column
            })
            .collect()
    }