Constraint-Based Very Large-Scale Neighborhood Search for Machine Reassignment

The Problem was posed by the ROADEF/EURO Challenge 2012.
See http://challenge.roadef.org/2012/en/ for the model and further details.

This is the final submission of Team J25 consisting of:
  Felix Brandt <brandt@fzi.de>
  Jochen Speck <speck@kit.edu>
  Markus Voelker <markus.voelker@kit.edu>

The presented approach is basically a very large-scale neighborhood search with
a constraint program (CP) to iteratively find improved solutions. In each
iteration a subset of processes (chosen by a neighborhood strategy) is "lifted",
i.e. considered for reassignment, while all other processes stay on their
current machine. Our constraint program then efficiently searches for promising
reassignments in the neighborhood. The overall search procedure alternates
between different neighborhood strategies until the time limit is reached.

As CP framework we use the open source toolkit Gecode in its 3.7.0 release.

All code is released under MIT license.

This folder contains the following classes/files:

Instance                  Representation of a problem instance
SchedulePlotter           Create HTML report from model and assignment
ReAssignment              Representation of the current solution state
ProcessFixing             Store of processes currently not available for reassignment

RescheduleSpace           Gecode search space of our model
ProcessPropagator         Custom propagator calculating cost of a process after assignment
CostPropagator            Custom propagator between a process' machine domain and its cost
BestCostBrancher          Custom brancher of our model

BaseSearch                Abstract local search procedure
IterativeSearch           Abstract iterative local search procedure
RandomSearch              Random local search
ProcessNeighborhoodSearch Local search lifting processes of similar size
TargetMoveSearch          Local search lifting a big process and smaller processes on a potential target machine
UndoMoveSearch            Local search trying to move processes back to their original machine