Justification Technique Generalizations

The justification technique was introduced various decades ago for the resource-constrained project scheduling problem, although it has rarely been used with the problem. Justification is a simple and quick technique which when applied to schedules produces a new schedule that is, at most, as long as the original schedule — and often shorter. A recent article (Valls et al, 2005), showed that incorporating justification in heuristic algorithms can produce a substancial improvement in the results obtained. These results have motivated us to generalise this technique in order to study it in greater depth. This paper proposes distinct forms and generalisations for the justification technique and studies the relation existing among sets of obtainable schedules. The obtained results show that the proposed generalisations are worthwhile. Several computational tests have been performed to ascertain the impact of the generalisations on algorithmic efficiency.