tokens: Previously , we had used a parallel split - apply - combine approach to study the performance of the commonly performed " RMSD fitting " analysis problem Khoshlessan:2017ab , ICCP-2018 , Fan:2019aa , which calculates the minimal root mean squared distance ( RMSD ) of the positions of a subset of atoms to a reference conformation under optimization of rigid body translations and rotationsLiu:2010kx , Lea96 , Mura:2014kx .