The program VinaMPI has been developed to enable massively large virtual drug 
screens on leadership-class computing resources, using a large number of cores 
to decrease the time-to-completion of the screen. VinaMPI is a massively 
parallel Message Passing Interface (MPI) program based on the multithreaded 
virtual docking program AutodockVina, and is used to distribute tasks while 
multithreading is used to speed-up individual docking tasks. VinaMPI uses a 
distribution scheme in which tasks are evenly distributed to the workers based 
on the complexity of each task, as defined by the number of rotatable bonds in 
each chemical compound investigated. VinaMPI efficiently handles multiple 
proteins in a ligand screen, allowing for high-throughput inverse docking that 
presents new opportunities for improving the efficiency of the drug discovery 
pipeline. VinaMPI successfully ran on 84,672 cores with a continual decrease in 
job completion time with increasing core count. The ratio of the number of tasks 
in a screening to the number of workers should be at least around 100 in order 
to have a good load balance and an optimal job completion time. The code is 
freely available and downloadable. Instructions for downloading and using the 
code are provided in the Supporting Information.