I know PetscOptionsGetScalar(), but do not know how to write the complex number in command line. I tried to write it in some forms but all did not work. Say, the options is -acomplex. I tried -acomplex 1.0+1.0i, or -acomplex 1.0+1.0*i, or -acomplex 1.0+1.0*I ... no one works. thank you, Hui