Due to the complexities of lattice sum calculations, the most costly aspects of the algorithm are the lattice minimisations of structures in the training set, which are needed to obtain Ω * s and U * inter,s , and the calculation of the derivatives of the residuals. Because the lattice minimisation and residual calculations for each structure are independent from one another, this enables their parallelisation. Parallelisation is implemented in CrystalEstimator using Message Passing Interface (MPI), where N c > 1 computing cores are distributed into N c -1 workers and 1 bookkeeper. The CrystalEstimator code can also support serial operation (i.e., N c = 1) where all calculations are performed on a single processor with no bookkeeper.