Department of Computer Science, K.U.Leuven, Leuven, Belgium
CW Reports vol:CW338
Trailing of bindings in the PARMA variable representation is expensive in time and space. We present two schemes that lower its cost: the first is a technique that halves the space cost of trailing in PARMA. It can be used with both conditional and unconditional trailing. It is illustrated and evaluated in the context of dProlog and in the Mercury backend of HAL. The second scheme combines a variant of a previously developed trailing analysis with the first technique. Empirical evidence shows the usefulness of these schemes and that the combination is more effective than each scheme apart.