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License: MIT alt text

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