share × free revisited

email amk ukcacuk Analyses for possible variable sharing and denite freeness are important both in the automatic parallelisation and in the optimisation of sequential logic programs In this paper a new ecient approach to analysis is described which can infer sharing and freeness information to an unusually high degree of accuracy The analysis exploits a conuence property of the unication algorithm to split the analysis into two distinct phases The two phase analysis improves eciency by enabling each phase of the analysis to manipulate relatively simple datastructures The precision follows from the combination of domains The analysis propagates groundness with the accuracy of sharing groups and yet infers sharing and freeness to a precision which exceeds that of a normal freeness analysis High precision compoundness information can be derived too The usefulness of the analysis is demonstrated with worked examples Correctness is formally proven Abstract interpretation for sharing and freeness are important topics of logic programmin