High performance computer (HPC) simulations provide helpful insights to the process of magnetic resonance image (MRI) generation, e.g. for general pulse sequence design and optimisation, artefact detection, validation of experimental results, hardware optimisation, MRI sample development and for education purposes. This manuscript presents the recently developed simulator JEMRIS (Jülich Environment for Magnetic Resonance Imaging Simulation). JEMRIS is developed in C++, the message passing is realised with the MPI library. The approach provides generally valid numerical solutions for the case of classical MR spin physics governed by the Bloch equations. The framework already serves as a tool in research projects, as will be shown for the important example of multidimensional, spatially-selective excitation.