We discuss the efficient implementation of model reduction methods
such as modal truncation, balanced truncation, and other
balancing-related truncation techniques, employing the idea of
spectral projection. Mostly, we will be concerned with the sign function method
which serves as the major computational tool of most of the discussed
algorithms for computing reduced-order models. Implementations for
large-scale problems based on parallelization or formatted arithmetic
will also be discussed. This chapter can also serve as a tutorial on
Gramian-based model reduction using spectral projection methods.
Keywords:
model reduction; spectral projection; sign function method;
balanced truncation; modal truncation