Group shopsschedulingwithmakespancriterionsubjecttorandomreleasedatesand processing times

This paperdealswithastochasticgroupshopschedulingproblem.Thegroupshopschedulingproblem is ageneralformulationthatincludestheothershopschedulingproblemssuchastheflowshop,thejob shop andtheopenshopschedulingproblems.Boththereleasedateofeachjobandtheprocessingtime of eachjoboneachmachinearerandomvariableswithknowndistributions.Theobjectiveistofindajob schedule whichminimizestheexpectedmakespan.First,theproblemisformulatedinaformofstochastic programming andthenalowerboundontheexpectedmakespanisproposedwhichmaybeusedasa measure forevaluatingtheperformanceofasolutionwithoutsimulating.Tosolvethestochasticproblem efficiently, asimulationoptimizationapproachisdevelopedthatisahybridofanantcolonyoptimization algorithm andaheuristicalgorithmtogenerategoodsolutionsandadiscreteeventsimulationmodel to evaluatetheexpectedmakespan.Theproposedapproachistestedoninstanceswheretherandom variables arenormally,exponentiallyoruniformlydistributedandgivespromisingresults.