Adjustment of heads and tails for the job-shop problem

The efficiency of recent enumerative methods for the job-shop problem crucially depends on immediate selections of disjunctive constraints leading to adjustment of heads and tails. This paper presents new investigations concerning this powerful tool. More efficient algorithms are proposed, and global operations are introduced. We also describe a new lower bound and a new branching scheme which are used to design a branch and bound method. Computational results show that these techniques permit to drastically reduce the size of the search trees.