About a year ago I wrote a review of Flare a tool for structure-based drug design.

The key new features of Flare V4 includes significant improvements to Free Energy Perturbation (FEP), new and improved force fields, new Dynamics analysis tools, plus new and improved GUI functionality.

The implementation of the Open Forcefield now allows users to update themselves.

FEP has been implemented in Flare DOI and this release improves performance.

In terms of speed, all FEP calculation in Flare V4 are significantly faster thanks to an improved algorithm with a 20% increase in performance, and they are fully parallelizable. This means that each bit of the transformation of one compound into another (the lambda windows) can be run on separate GPUs: the results will be merged at the end of the calculation. This can bring the calculation time for a single transformation on a medium-sized protein to less than 2 hours on a small cluster of 10 GPUs (for example AWS g4dn.xlarge, Tesla T4 spot instances).