If the circuit has fewer gates, then pad it with dummy gates up to the multiplicative subgroup size.

Curves for PLONK and Halo 2 are normally chosen to have a choice of multiplicative subgroups with a wide range of sizes. If the scalar field is F_{q}, then any smallish factor of q-1 can be used as the subgroup size. For example, the fields of the Pasta curves that were generated for Halo 2 have q-1 as a multiple of 2^{32}, so any power of 2 up to 2^{32} can be used. Using power-of-2 subgroups is also the most efficient option for the FFTs used to implement polynomial arithmetic.