I'm doing a course of XFEM in Computational Mechanics, for a better understanding of the topic i need to work on a couple of questions given by the professor;

i need to discuss the following topic:

Consider we are supposed to write a very efficient code with X-FEM to perform shape optimization on fixed grids;

Discuss in details how you would design such a code (what is the difference from a standard finite element code?)

Discuss the performance issues 

at the end i need to consider a similar question but now for a two-phase material for which i need to optimize the location of the material interface,.

i appreciate any answer or reference please

thanks