Package org.jacop.constraints.knapsack

Class Tree

  • public class Tree
extends java.lang.Object
    This tree is a main data structure used and required by Knapsack constraint.
    Version:
    4.8

    • Field Summary

      Fields 
      Modifier and Type Field Description
      int alreadyObtainedProfit
      It specifies the already obtained profit due to the items which are already included in the solution.
      int alreadyUsedCapacity
      It specifies the already used capacity due to the items which are already included in the solution.
      int availableWeightOfCriticalItem
      It specifies the fraction of the critical item which has been not included in the optimal non-integral solution.
      TreeLeaf criticalLeaf
      It specifies the leaf containing the critical item.
      int criticalLeftLeaf
      It specifies the leaf containing the left most item which is being used during computeForbidden().
      int criticalRightLeaf
      It specifies the leaf containing the last right item which is being used during computeMandatory().
      (package private) TreeNode currentNode
      It specifies the current right item of the tree which have been yet included in computation of replaceable weight.
      (package private) int currentProfit
      It specifies the current profit obtained by all already traversed right items.
      (package private) int currentWeight
      It specifies the currentWeight from which searching for next mandatory item starts from.
      boolean exhaustedLeftItems
      It specifies that computeForbidden part of the consistency function has run out of left mandatory items.
      boolean exhaustedRightItems
      It specifies if the mandatory check has run out of right items to complement mandatory items.
      TreeLeaf first
      It specifies the first (counting from left to right), the most efficient item in the tree.
      TreeLeaf last
      It specifies the last (counting from left to right), the least efficient item in the tree.
      double optimalProfit
      It specifies the optimalProfit of possibly non-integral solution generated by LP relaxation.
      (package private) double profitFromCriticalLeft
      It specifies the profit obtained from the remaining part of the critical item.
      (package private) double profitFromCriticalTaken
      It specifies the profit obtained from the remaining part of the critical item.
      TreeNode root
      It specifies the root of the tree.
      int takenWeightOfCriticalItem
      It specifies how much weight is used by an optimal non-fractional solution.

    • Constructor Summary

      Constructors 
      Constructor Description
      Tree​(KnapsackItem[] items, java.util.Map<IntVar,​TreeLeaf> varPositionMaping, TreeLeaf[] leaves, IntVar zero)
      It constructs a tree out of the list of items and creates proper supporting structures.
      Tree​(Tree tree)
      It creates a tree by making a shallow copy.
      Tree​(TreeNode node)
      Create a single node tree.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      int computeIntrusionWeight​(int weightOfItemChecked, int maxNoOfItems, int profitOfItemChecked, double efficiencyOfItemChecked, double profitSlack)
      It returns the amount of weight of a given item being checked which can be replaced by Right items given the amount of profitSlack.
      int computeMinProfit​(int minWeight)
      It computes the minimum of capacity variable for knapsack constraint given the minimum requirement for profit.
      int computeMinWeight​(int minProfit)
      It computes the minimum of capacity variable for knapsack constraint given the minimum requirement for profit.
      int computeReplacableWeight​(int weightOfItemChecked, int maxNoOfItems, int profitOfItemChecked, double efficiencyOfItemChecked, double profitSlack)
      It returns the amount of weight of a given item being checked which can be replaced by Right items given the amount of profitSlack.
      TreeLeaf findNextLeafAtLeastOfWeight​(TreeLeaf leaf, int weight)
      It finds next leaf of a maximum weight of at least weight, so it can have some parts of it mandatory.
      TreeLeaf findPreviousLeafAtLeastOfWeight​(TreeLeaf leaf, int weight)
      It finds previous leaf of a maximum weight of at least weight, so it can have some parts of it forbidden.
      int getCriticalPosition​(int capacity)
      It finds a leaf which reaches the limit of the given capacity.
      TreeLeaf getFirst()
      Used to search for mandatory
      TreeLeaf getLast()
      It returns the last (the least efficient) item in the tree.
      void initializeComputeForbidden()
      It initializes the private variables required by computation of how much weight we can replace for any Left item.
      void initializeComputeMandatory()
      It initializes the private variables required by computation of how much weight we can replace for any Left item.
      Tree merge​(Tree that)
      A merge method for trees, it added a new root from the ancients
      void recompute()
      It recomputes all the attributes of the internal nodes of the knapsack tree.
      java.lang.String toString()  
      void updateCritical​(int capacity)
      It updates information about the critical item, as well as information about fraction of critical item which is not taken.
      void updateFromList​(java.util.List<TreeLeaf> list, int startingPosition)
      Used for updating the tree using a list of nodes that have changed.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Field Detail

      • root

        public final TreeNode root
        It specifies the root of the tree.

      • criticalLeaf

        public TreeLeaf criticalLeaf
        It specifies the leaf containing the critical item. The critical item is the one used partially by Linear Programming approach.

      • criticalRightLeaf

        public int criticalRightLeaf
        It specifies the leaf containing the last right item which is being used during computeMandatory(). if max() of the right item after criticalRight is changed then it can be safely ignored.

      • criticalLeftLeaf

        public int criticalLeftLeaf
        It specifies the leaf containing the left most item which is being used during computeForbidden(). if min() of the left item before criticalLeft is changed then it can be safely ignored.

      • first

        public TreeLeaf first
        It specifies the first (counting from left to right), the most efficient item in the tree.

      • last

        public TreeLeaf last
        It specifies the last (counting from left to right), the least efficient item in the tree.

      • optimalProfit

        public double optimalProfit
        It specifies the optimalProfit of possibly non-integral solution generated by LP relaxation.

      • availableWeightOfCriticalItem

        public int availableWeightOfCriticalItem
        It specifies the fraction of the critical item which has been not included in the optimal non-integral solution.

      • takenWeightOfCriticalItem

        public int takenWeightOfCriticalItem
        It specifies how much weight is used by an optimal non-fractional solution.

      • alreadyObtainedProfit

        public int alreadyObtainedProfit
        It specifies the already obtained profit due to the items which are already included in the solution.

      • alreadyUsedCapacity

        public int alreadyUsedCapacity
        It specifies the already used capacity due to the items which are already included in the solution.

      • currentNode

        TreeNode currentNode
        It specifies the current right item of the tree which have been yet included in computation of replaceable weight.

      • currentWeight

        int currentWeight
        It specifies the currentWeight from which searching for next mandatory item starts from. Only items with weight greater or equal to currentWeight can be (partially) mandatory.

      • currentProfit

        int currentProfit
        It specifies the current profit obtained by all already traversed right items.

      • profitFromCriticalLeft

        double profitFromCriticalLeft
        It specifies the profit obtained from the remaining part of the critical item.

      • profitFromCriticalTaken

        double profitFromCriticalTaken
        It specifies the profit obtained from the remaining part of the critical item.

      • exhaustedRightItems

        public boolean exhaustedRightItems
        It specifies if the mandatory check has run out of right items to complement mandatory items.

      • exhaustedLeftItems

        public boolean exhaustedLeftItems
        It specifies that computeForbidden part of the consistency function has run out of left mandatory items.

    • Constructor Detail

      • Tree

        public Tree​(TreeNode node)
        Create a single node tree.
        Parameters:
        node - a root of this one-node tree.

      • Tree

        public Tree​(Tree tree)
        It creates a tree by making a shallow copy.
        Parameters:
        tree - tree to be constructed

      • Tree

        public Tree​(KnapsackItem[] items,
            java.util.Map<IntVar,​TreeLeaf> varPositionMaping,
            TreeLeaf[] leaves,
            IntVar zero)
        It constructs a tree out of the list of items and creates proper supporting structures. It assumes the list of items is greater than 1.
        Parameters:
        items - knapsack items used to create the tree.
        varPositionMaping - mapping of variables into positions within the tree.
        leaves - array of leaves of the created tree.
        zero - it specifies a variable equal to value 0.

    • Method Detail

      • merge

        public Tree merge​(Tree that)
        A merge method for trees, it added a new root from the ancients
        Parameters:
        that - A tree that is being merged with this tree.
        Returns:
        The tree resulting of the merge of this and that

      • updateCritical

        public void updateCritical​(int capacity)
        It updates information about the critical item, as well as information about fraction of critical item which is not taken.
        Parameters:
        capacity - available capacity to be used by knapsack.

      • getCriticalPosition

        public int getCriticalPosition​(int capacity)
        It finds a leaf which reaches the limit of the given capacity. Items weight is added from the most efficient to the least efficient.
        Parameters:
        capacity - available capacity to be used by knapsack.
        Returns:
        the position of the item.

      • getFirst

        public TreeLeaf getFirst()
        Used to search for mandatory
        Returns:
        The first item

      • getLast

        public TreeLeaf getLast()
        It returns the last (the least efficient) item in the tree. It is a starting leaf for computeForbidden() part.
        Returns:
        The last item

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • updateFromList

        public void updateFromList​(java.util.List<TreeLeaf> list,
                           int startingPosition)
        Used for updating the tree using a list of nodes that have changed.
        Parameters:
        list - list of leaves that needs to be updated.
        startingPosition - it specifies the first leaf in the array which has not been updated before.

      • recompute

        public void recompute()
        It recomputes all the attributes of the internal nodes of the knapsack tree.

      • initializeComputeMandatory

        public void initializeComputeMandatory()
        It initializes the private variables required by computation of how much weight we can replace for any Left item.

      • computeReplacableWeight

        public int computeReplacableWeight​(int weightOfItemChecked,
                                   int maxNoOfItems,
                                   int profitOfItemChecked,
                                   double efficiencyOfItemChecked,
                                   double profitSlack)
        It returns the amount of weight of a given item being checked which can be replaced by Right items given the amount of profitSlack.
        Parameters:
        weightOfItemChecked - the weight of item being checked.
        maxNoOfItems - the maximum number which can be taken of checked items.
        profitOfItemChecked - the profit of the item being checked.
        efficiencyOfItemChecked - the efficiency of the item being checked.
        profitSlack - the amount of reserve profit which can be sacrificed before violating the constraint.
        Returns:
        the amount of weight of a given item that can be replaced by Right items without violating the constraint.

      • findNextLeafAtLeastOfWeight

        public TreeLeaf findNextLeafAtLeastOfWeight​(TreeLeaf leaf,
                                            int weight)
        It finds next leaf of a maximum weight of at least weight, so it can have some parts of it mandatory.
        Parameters:
        leaf - starting leaf, the result must be to the right of this leaf.
        weight - weight condition which must be satisfied by the found leaf.
        Returns:
        tree leaf on the right to the supplied leaf with at least specified weight.

      • initializeComputeForbidden

        public void initializeComputeForbidden()
        It initializes the private variables required by computation of how much weight we can replace for any Left item.

      • computeIntrusionWeight

        public int computeIntrusionWeight​(int weightOfItemChecked,
                                  int maxNoOfItems,
                                  int profitOfItemChecked,
                                  double efficiencyOfItemChecked,
                                  double profitSlack)
        It returns the amount of weight of a given item being checked which can be replaced by Right items given the amount of profitSlack.
        Parameters:
        weightOfItemChecked - the weight of item being checked.
        maxNoOfItems - the maximum number which can be taken of checked items.
        profitOfItemChecked - the profit of the item being checked.
        efficiencyOfItemChecked - the efficiency of the item being checked.
        profitSlack - the amount of reserve profit which can be sacrificed before violating the constraint.
        Returns:
        the amount of weight of a given item that can be replaced by Right items without violating the constraint.

      • findPreviousLeafAtLeastOfWeight

        public TreeLeaf findPreviousLeafAtLeastOfWeight​(TreeLeaf leaf,
                                                int weight)
        It finds previous leaf of a maximum weight of at least weight, so it can have some parts of it forbidden.
        Parameters:
        leaf - starting leaf, the result must be to the left of this leaf.
        weight - weight condition which must be satisfied by the found leaf.
        Returns:
        tree leaf on the left to the supplied leaf with at least specified weight.

      • computeMinWeight

        public int computeMinWeight​(int minProfit)
        It computes the minimum of capacity variable for knapsack constraint given the minimum requirement for profit.
        Parameters:
        minProfit - minimum profit obtained by the knapsack.
        Returns:
        it returns the minimum required weight to satisfy min profit requirements.

      • computeMinProfit

        public int computeMinProfit​(int minWeight)
        It computes the minimum of capacity variable for knapsack constraint given the minimum requirement for profit.
        Parameters:
        minWeight - - the minimum of weight within a knapsack.
        Returns:
        it returns the minimum required weight to satisfy min profit requirements.