  During the course of the last decade, traveling wave accelerating structures
for a future Linear Collider have been the object of intense R&D efforts. An
important problem is the efficient computation of the long range wakefield with
the ability to include small alignment and tuning errors. To that end, SLAC has
developed an RF circuit model with a demonstrated ability to reproduce
experimentally measured wakefields. The wakefield computation involves the
repeated solution of a deterministic system of equations over a range of
frequencies. By taking maximum advantage of the sparsity of the equations, we
have achieved significant performance improvements. These improvements make it
practical to consider simulations involving an entire linac ($\sim 10^3$
structures). One might also contemplate assessing, in real time, the impact of
fabrication errors on the wakefield as an integral part of quality control.
