  Poor computing efficiency of precision event generators for LHC physics has
become a bottleneck for Monte-Carlo event simulation campaigns. We provide
solutions to this problem by focusing on two major components of
general-purpose event generators: The PDF evaluator and the matrix-element
generator. For a typical production setup in the ATLAS experiment, we show that
the two can consume about 80% of the total runtime. Using NLO simulations of
$pp\to\ell^+\ell^-+\text{jets}$ and $pp\to t\bar{t}+\text{jets}$ as an example,
we demonstrate that the computing footprint of LHAPDF and Sherpa can be reduced
by factors of order 10, while maintaining the formal accuracy of the event
sample. The improved codes are made publicly available.
