  The last milestone achievement for the roundoff-error-free solution of
general mixed integer programs over the rational numbers was a hybrid-precision
branch-and-bound algorithm published by Cook, Koch, Steffy, and Wolter in 2013.
  We describe a substantial revision and extension of this framework that
integrates symbolic presolving, features an exact repair step for solutions
from primal heuristics, employs a faster rational LP solver based on LP
iterative refinement, and is able to produce independently verifiable
certificates of optimality.
  We study the significantly improved performance and give insights into the
computational behavior of the new algorithmic components.
  On the MIPLIB 2017 benchmark set, we observe an average speedup of 6.6x over
the original framework and 2.8 times as many instances solved within a time
limit of two hours.
