Package minicp.cp

Class Factory

java.lang.Object
minicp.cp.Factory
public final class Factory extends Object
Factory to create Solver, IntVar, Constraint and some modeling utility methods. Example for the n-queens problem: 
 
  Solver cp = Factory.makeSolver(false);
  IntVar[] q = Factory.makeIntVarArray(cp, n, n);
  for (int i = 0; i < n; i++)
    for (int j = i + 1; j < n; j++) {
      cp.post(Factory.notEqual(q[i], q[j]));
      cp.post(Factory.notEqual(q[i], q[j], j - i));
      cp.post(Factory.notEqual(q[i], q[j], i - j));
    }
  search.onSolution(() ->
    System.out.println("solution:" + Arrays.toString(q))
  );
  DFSearch search = Factory.makeDfs(cp,firstFail(q));
  SearchStatistics stats = search.solve();

  • Method Details

    • makeSolver

      public static Solver makeSolver()
      Creates a constraint programming solver
      Returns:
      a constraint programming solver with trail-based memory management

    • makeSolver

      public static Solver makeSolver(boolean byCopy)
      Creates a constraint programming solver
      Parameters:
      byCopy - a value that should be true to specify copy-based state management or falso for a trail-based memory management
      Returns:
      a constraint programming solver

    • makeIntVar

      public static IntVar makeIntVar(Solver cp, int sz)
      Creates a variable with a domain of specified arity.
      Parameters:
      cp - the solver in which the variable is created
      sz - a positive value that is the size of the domain
      Returns:
      a variable with domain equal to the set {0,...,sz-1}

    • makeIntVar

      public static IntVar makeIntVar(Solver cp, int min, int max)
      Creates a variable with a domain equal to the specified range.
      Parameters:
      cp - the solver in which the variable is created
      min - the lower bound of the domain (included)
      max - the upper bound of the domain (included) max > min
      Returns:
      a variable with domain equal to the set {min,...,max}

    • makeIntVar

      public static IntVar makeIntVar(Solver cp, Set<Integer> values)
      Creates a variable with a domain equal to the specified set of values.
      Parameters:
      cp - the solver in which the variable is created
      values - a set of values
      Returns:
      a variable with domain equal to the set of values

    • makeBoolVar

      public static BoolVar makeBoolVar(Solver cp)
      Creates a boolean variable.
      Parameters:
      cp - the solver in which the variable is created
      Returns:
      an uninstantiated boolean variable

    • makeIntVarArray

      public static IntVar[] makeIntVarArray(Solver cp, int n, int sz)
      Creates an array of variables with specified domain size.
      Parameters:
      cp - the solver in which the variables are created
      n - the number of variables to create
      sz - a positive value that is the size of the domain
      Returns:
      an array of n variables, each with domain equal to the set {0,...,sz-1}

    • makeIntVarArray

      public static IntVar[] makeIntVarArray(Solver cp, int n, int min, int max)
      Creates an array of variables with specified domain bounds.
      Parameters:
      cp - the solver in which the variables are created
      n - the number of variables to create
      min - the lower bound of the domain (included)
      max - the upper bound of the domain (included) max > min
      Returns:
      an array of n variables each with a domain equal to the set {min,...,max}

    • makeIntVarArray

      public static IntVar[] makeIntVarArray(int n, Function<Integer,IntVar> body)
      Creates an array of variables with specified lambda function
      Parameters:
      n - the number of variables to create
      body - the function that given the index i in the array creates/map the corresponding IntVar
      Returns:
      an array of n variables with variable at index i generated as body.get(i)

    • makeDfs

      public static DFSearch makeDfs(Solver cp, Supplier<Procedure[]> branching)
      Creates a Depth First Search with custom branching heuristic 
       // Example of binary search: At each node it selects
 // the first free variable qi from the array q,
 // and creates two branches qi=v, qi!=v where v is the min value domain
 
 DFSearch search = Factory.makeDfs(cp, () -> {
     IntVar qi = Arrays.stream(q).reduce(null, (a, b) -> b.size() > 1 && a == null ? b : a);
     if (qi == null) {
        return return EMPTY;
     } else {
        int v = qi.min();
        Procedure left = () -> cp.post(equal(qi, v)); // left branch
        Procedure right = () -> cp.post(notEqual(qi, v)); // right branch
        return branch(left, right);
     }
 });
      Parameters:
      cp - the solver that will be used for the search
      branching - a generator that is called at each node of the depth first search tree to generate an array of Procedure objects that will be used to commit to child nodes. It should return BranchingScheme.EMPTY whenever the current state is a solution.
      Returns:
      the depth first search object ready to execute with DFSearch.solve() or DFSearch.optimize(Objective) using the given branching scheme
      See Also:

    • mul

      public static IntVar mul(IntVar x, int a)
      A variable that is a view of x*a.
      Parameters:
      x - a variable
      a - a constant to multiply x with
      Returns:
      a variable that is a view of x*a

    • minus

      public static IntVar minus(IntVar x)
      A variable that is a view of -x.
      Parameters:
      x - a variable
      Returns:
      a variable that is a view of -x

    • plus

      public static IntVar plus(IntVar x, int v)
      A variable that is a view of x+v.
      Parameters:
      x - a variable
      v - a value
      Returns:
      a variable that is a view of x+v

    • minus

      public static IntVar minus(IntVar x, int v)
      A variable that is a view of x-v.
      Parameters:
      x - a variable
      v - a value
      Returns:
      a variable that is a view of x-v

    • not

      public static BoolVar not(BoolVar b)
      A boolean variable that is a view of !b.
      Parameters:
      b - a boolean variable
      Returns:
      a boolean variable that is a view of !b

    • abs

      public static IntVar abs(IntVar x)
      Computes a variable that is the absolute value of the given variable. This relation is enforced by the Absolute constraint posted by calling this method.
      Parameters:
      x - a variable
      Returns:
      a variable that represents the absolute value of x

    • maximum

      public static IntVar maximum(IntVar... x)
      Computes a variable that is the maximum of a set of variables. This relation is enforced by the Maximum constraint posted by calling this method.
      Parameters:
      x - the variables on which to compute the maximum
      Returns:
      a variable that represents the maximum on x
      See Also:

    • minimum

      public static IntVar minimum(IntVar... x)
      Computes a variable that is the minimum of a set of variables. This relation is enforced by the Maximum constraint posted by calling this method.
      Parameters:
      x - the variables on which to compute the minimum
      Returns:
      a variable that represents the minimum on x
      See Also:

    • equal

      public static Constraint equal(IntVar x, int v)
      Returns a constraint imposing that the variable is equal to some given value.
      Parameters:
      x - the variable to be assigned to v
      v - the value that must be assigned to x
      Returns:
      a constraint so that x = v

    • lessOrEqual

      public static Constraint lessOrEqual(IntVar x, int v)
      Returns a constraint imposing that the variable less or equal to some given value.
      Parameters:
      x - the variable that is constrained bo be less or equal to v
      v - the value that must be the upper bound on x
      Returns:
      a constraint so that x <= v

    • largerOrEqual

      public static Constraint largerOrEqual(IntVar x, int v)
      Returns a constraint imposing that the variable larger or equal to some given value.
      Parameters:
      x - the variable that is constrained bo be larger or equal to v
      v - the value that must be the lower bound on x
      Returns:
      a constraint so that x >= v

    • notEqual

      public static Constraint notEqual(IntVar x, int v)
      Returns a constraint imposing that the variable is different from some given value.
      Parameters:
      x - the variable that is constrained bo be different from v
      v - the value that must be different from x
      Returns:
      a constraint so that x != y

    • notEqual

      public static Constraint notEqual(IntVar x, IntVar y)
      Returns a constraint imposing that the two different variables must take different values.
      Parameters:
      x - a variable
      y - a variable
      Returns:
      a constraint so that x != y

    • equal

      public static Constraint equal(IntVar x, IntVar y)
      Returns a constraint imposing that the two different variables must take the value.
      Parameters:
      x - a variable
      y - a variable
      Returns:
      a constraint so that x = y

    • notEqual

      public static Constraint notEqual(IntVar x, IntVar y, int c)
      Returns a constraint imposing that the the first variable differs from the second one minus a constant value.
      Parameters:
      x - a variable
      y - a variable
      c - a constant
      Returns:
      a constraint so that x != y+c

    • isEqual

      public static BoolVar isEqual(IntVar x, int c)
      Returns a boolean variable representing whether one variable is equal to the given constant. This relation is enforced by the IsEqual constraint posted by calling this method.
      Parameters:
      x - the variable
      c - the constant
      Returns:
      a boolean variable that is true if and only if x takes the value c
      See Also:

    • isLessOrEqual

      public static BoolVar isLessOrEqual(IntVar x, int c)
      Returns a boolean variable representing whether one variable is less or equal to the given constant. This relation is enforced by the IsLessOrEqual constraint posted by calling this method.
      Parameters:
      x - the variable
      c - the constant
      Returns:
      a boolean variable that is true if and only if x takes a value less or equal to c

    • isLess

      public static BoolVar isLess(IntVar x, int c)
      Returns a boolean variable representing whether one variable is less than the given constant. This relation is enforced by the IsLessOrEqual constraint posted by calling this method.
      Parameters:
      x - the variable
      c - the constant
      Returns:
      a boolean variable that is true if and only if x takes a value less than c

    • isLargerOrEqual

      public static BoolVar isLargerOrEqual(IntVar x, int c)
      Returns a boolean variable representing whether one variable is larger or equal to the given constant. This relation is enforced by the IsLessOrEqual constraint posted by calling this method.
      Parameters:
      x - the variable
      c - the constant
      Returns:
      a boolean variable that is true if and only if x takes a value larger or equal to c

    • isLarger

      public static BoolVar isLarger(IntVar x, int c)
      Returns a boolean variable representing whether one variable is larger than the given constant. This relation is enforced by the IsLessOrEqual constraint posted by calling this method.
      Parameters:
      x - the variable
      c - the constant
      Returns:
      a boolean variable that is true if and only if x takes a value larger than c

    • lessOrEqual

      public static Constraint lessOrEqual(IntVar x, IntVar y)
      Returns a constraint imposing that the a first variable is less or equal to a second one.
      Parameters:
      x - a variable
      y - a variable
      Returns:
      a constraint so that x <= y

    • largerOrEqual

      public static Constraint largerOrEqual(IntVar x, IntVar y)
      Returns a constraint imposing that the a first variable is larger or equal to a second one.
      Parameters:
      x - a variable
      y - a variable
      Returns:
      a constraint so that x >= y

    • element

      public static IntVar element(int[] array, IntVar y)
      Returns a variable representing the value in an array at the position specified by the given index variable This relation is enforced by the Element1D constraint posted by calling this method.
      Parameters:
      array - the array of values
      y - the variable
      Returns:
      a variable equal to array[y]

    • element

      public static IntVar element(int[][] matrix, IntVar x, IntVar y)
      Returns a variable representing the value in a matrix at the position specified by the two given row and column index variables This relation is enforced by the Element2D constraint posted by calling this method.
      Parameters:
      matrix - the n x m 2D array of values
      x - the row variable with domain included in 0..n-1
      y - the column variable with domain included in 0..m-1
      Returns:
      a variable equal to matrix[x][y]

    • sum

      public static IntVar sum(IntVar... x)
      Returns a variable representing the sum of a given set of variables. This relation is enforced by the Sum constraint posted by calling this method.
      Parameters:
      x - the n variables to sum
      Returns:
      a variable equal to x[0]+x[1]+...+x[n-1]

    • sum

      public static Constraint sum(IntVar[] x, IntVar y)
      Returns a sum constraint.
      Parameters:
      x - an array of variables
      y - a variable
      Returns:
      a constraint so that y = x[0]+x[1]+...+x[n-1]

    • sum

      public static Constraint sum(IntVar[] x, int y)
      Returns a sum constraint.
      Parameters:
      x - an array of variables
      y - a constant
      Returns:
      a constraint so that y = x[0]+x[1]+...+x[n-1]

    • sum

      public static Constraint sum(int y, IntVar... x)
      Returns a sum constraint.

      Uses a _parameter pack_ to automatically bundle a list of IntVar as an array

      Parameters:
      y - the target value for the sum (a constant)
      x - a parameter pack of IntVar representing an array of variables
      Returns:
      a constraint so that y = x[0] + ... + x[n-1]

    • allDifferent

      public static Constraint allDifferent(IntVar[] x)
      Returns a binary decomposition of the allDifferent constraint.
      Parameters:
      x - an array of variables
      Returns:
      a constraint so that x[i] != x[j] for all i < j

    • allDifferentDC

      public static Constraint allDifferentDC(IntVar[] x)
      Returns an allDifferent constraint that enforces domain consistency.
      Parameters:
      x - an array of variables
      Returns:
      a constraint so that x[i] != x[j] for all i < j