  While implicit Runge--Kutta methods possess high order accuracy and important
stability properties, implementation difficulties and the high expense of
solving the coupled algebraic system at each time step are frequently cited as
impediments. We present IIrksome, a high-level library for manipulating UFL
(Unified Form Language) expressions of semidiscrete variational forms to obtain
UFL expressions for the coupled Runge--Kutta stage equations at each time step.
Irksome works with the Firedrake package to enable the efficient solution of
the resulting coupled algebraic systems. Numerical examples confirm the
efficacy of the software and our solver techniques for various problems.
