xflp

xflp is a solver for truck loading problems in 3D with real world constraints

It supports:

• single or multiple bin packing
• rotating of items for 1 axis
• simulation of loading and unloading of items
• Constraints:
  • Max height of loading space
  • Max weight of loading space
  • Max bearing weight of each item
  • last in, first out condition
• consideration of stacking groups
• consideration of container types
• consideration of immersive depth during stacking
• consideration of permissible axle load (2 axles)

Optimization:

• Construction heuristic
• GRASP heuristic
  • Swap and relocate neighborhood search

Usage

XFLP xflp = new XFLP();
xflp.addContainer().setLength(13500).setWidth(2500).setHeight(3000).setMaxWeight(25000);
xflp.addItem().setExternID("Packet 1").setLength(13500).setWidth(2500).setHeight(3000).setWeight(25000);
xflp.addItem().setExternID("Packet 2").setLength(13500).setWidth(2500).setHeight(3000).setWeight(25000);
xflp.addItem().setExternID("Packet 3").setLength(13500).setWidth(2500).setHeight(3000).setWeight(25000);

xflp.executeLoadPlanning();

LPReport report = xflp.getReport();
int nbrOfUnloadedPackages = report.getSummary().getNbrOfUnLoadedPackages();

License

This software is released under [MIT License] (https://opensource.org/licenses/MIT)

Change log

0.6.5 - New parameter for maximal number of items

  XFLP xflp = new XFLP()
  xflp.getParameter().setLifoImportance(1)

  xflp.addItem().setExternID("P1")
  ...
  xflp.addItem().setExternID("P100")
  xflp.getParameter().setMaxNbrOfItems(23)

  xflp.executeLoadPlanning()
  assert xflp.getReport()[0].getPackageEvents().size() == 23

0.6.1 - Fixed Location feature

• User can set loading and unloading location for each item. This is useful during Vehicle Routing, when sequences of loading and unloading need to be checked. Here was a bug in code, where locations were not sorted in correct order. This is fixed now, but there are prerequisits:
  • The name of a location (load or unload) must correspond with the ordering in sequence.
  • The LIFO loading constraint must be activated as it is not default.
  • Example for infeasible solution

  XFLP xflp = new XFLP()
  xflp.getParameter().setLifoImportance(1)
  
  xflp.addItem().setExternID("P1").setLoadingLocation("Loc 1").setUnloadingLocation("Loc 3")
  xflp.addItem().setExternID("P2").setLoadingLocation("Loc 2").setUnloadingLocation("Loc 4")
  
  xflp.executeLoadPlanning()
  assert xflp.getReport().getUnplannedPackages().size() > 0
  

0.6.0 - Update to Java 17, permissible axle load and more

• Changed xflp to Java 17. Due to use of records, xflp is not compatible with Java < 17 anymore.
• Add space-based checking when items are added and removed in a container. This improves the planning performance and reduces the code complexity.
• Add constraint: permissible axle load for 2 axles

0.5.2 - Performance upgrade

• Improved bearing check by storing bearing capacities during container-adding.
  • For big problems the runtime improves by 43%.
• Refactored and removed old code

0.5.1 - Performance upgrade

• Add spaces for faster checking of possible insert positions
  • Each position defines a list of spaces, where items might fit into.
  • Adding new item means complex calculation/correction of spaces
  • Check, whether item fits at a certain position is reduced from O(n) to O(1)
    • For big problems the runtime improves by factor 3.
• Refactorings of optimization types
• Minor refactoring of ground contact checking
• Internal refactorings

0.5.0 - Performance upgrade

• Refactoring of container code
  • Split algorithmic functions to service classes
  • Add general definition of containers
  • Have at least 2 implementations of container:
    • Items can be added and removed (current implementation)
    • Items can only be added. Implementation can be way simpler and performance is better.
• Refactoring of current container service methods, which improves performance
• Added check for duplicate positions, which maybe bring a bit of performance
• Import function checks, which type of container is necessary.
• After import, some values of items are checked for validity.

0.4.1

• Add immersive depth

0.4.0 - More restrictions

• Add restriction, that one item must be fully placed on top of one item
  • Business motivation: Certain packages may have restriction due to shoulder or feet forms, that stacking on multiple items is not possible.
• Fixed copyright information
• Refactored import classes
• Use specific exception instead of runtime exceptions

0.3.2

• Added SpotBugs in build process to find smellies
• Fixed some smellies
  • In many cases a XFLPException is thrown instead of IllegalArgumentExceptions

0.3.1

• "Fast Fixed solver" uses new width proportion factor for choosing the next insert position

0.3.0 - Stacking groups

• Fix of stacking group feature
• Added a priorization criteria for choosing the next insert position. It takes the proportion of the item to the container into account.
• More reasonable structure of planning heuristics

0.2.0

• First stable release