Implementing the Generalised Hybrid Monte-Carlo algorithm

UKQCD's dynamical fermion project uses the Generalised Hybrid Monte Carlo (GHMC) algorithm to generate QCD gauge configurations for a non-perturbatively O(a) improved Wilson action with two degenerate sea-quark flavours. We describe our implementation of the algorithm on the Cray-T3E, concentrating on issues arising from code verification and performance optimisation, such as parameter tuning, reversibility, the effect of precision, the choice of matrix inverter, and the behaviour of different molecular dynamics integration schemes.