dgt with real-valued input 'f'
If f is with a real-valued dtype, dgt(f=f) computes a wrong matrix, not equivalent to dgt(f=f.astype(complex)), with some reshaping issue.
If f is with a real-valued dtype, dgt(f=f) computes a wrong matrix, not equivalent to dgt(f=f.astype(complex)), with some reshaping issue.