Implementation note: pcoef() is not optimized away, which means that c[16] (stack) is actually filled and read again once, resulting in a lot of uneccessary mov instructions. Need to find an alternative implementation which guarantees inlining.
Member eig (const SMatrix< N, N, NumType > &a, SVector< N, std::complex< NumType > > &lambda, SMatrix< N, N, std::complex< NumType > > &v)