Function balance_mix 

pub fn balance_mix(
    mode: Mode,
    budget: &Budget,
    cx: &Context,
    slots: &mut [Slot],
) -> Powers

The sign/verify split (summing to 100 %) that maximizes min(sign, verify / mix): what the B key does. With mix = 0 only signing counts. Returns the chosen powers; the slots are left at them.

The search runs the sign power in 4 % steps, then refines around the best in 1 % and 0.5 % steps.