  We present an algorithm to determine topological invariants of inhomogeneous
systems, such as alloys, disordered crystals, or amorphous systems. Based on
the kernel polynomial method, our algorithm allows us to study samples with
more than $10^7$ degrees of freedom. Our method enables the study of large
complex compounds, where disorder is inherent to the system. We use it to
analyse Pb$_{1-x}$Sn$_{x}$Te and tighten the critical concentration for the
phase transition.

Mesoscale and Nanoscale Physics;Disordered Systems and Neural Networks