In the SAMPL challenge, as for ABFE calculations in general, one of the most frequently used methods is umbrella sampling (US). The idea of US is to create a set of reference configurations along a predefined reaction coordinate, for example by pulling a molecule from another molecule, and to run MD for these independent "umbrellas" while restraining the sampling to the region around the reference configurations along the chosen reaction coordinate. These simulations are independent and can hence be performed in parallel. After the US simulations have sufficiently converged, the umbrellas are unbiased, for example with the weighted histogram analysis method (WHAM), to obtain the potential of mean force (PMF) from which the binding affinity is inferred. In what follows, we refer to the whole procedure, which includes the creation of the reference configurations along the reaction coordinate, the MD simulations of the individual umbrellas, and their transformation into a PMF, as a single 'repeat'. The popularity of the US is largely because of its availability in the popular MD software packages, tutorials, and automatic tools for setting up and postprocessing the simulations.