- How disjunctive constraints can be expressed in Cream?
Cream has no disjunctive constraints, such as

`(x > 0) or (y > 0)`

. However, you can encode it in Cream as follows. Or, you can simply use`x.max(y).gt(0)`

in this case.Network net = new Network(); IntVariable x = new IntVariable(net, -1, 1, "x"); IntVariable y = new IntVariable(net, -1, 1, "y"); // x > 0 or y > 0 IntVariable c1 = x.sign().max(0); IntVariable c2 = y.sign().max(0); // c1 or c2 --> c1 max c2 c1.max(c2).gt(0);

- How conditional constraints can be expressed in Cream?
Cream has no conditional constraints, such as

`if (x > 0) then (y > 0) else (z > 0)`

. However, you can encode it in Cream as follows.Network net = new Network(); IntVariable x = new IntVariable(net, 0, 1, "x"); IntVariable y = new IntVariable(net, 0, 1, "y"); IntVariable z = new IntVariable(net, 0, 1, "z"); // if x > 0 then y > 0 else z > 0 IntVariable c1 = x.sign().max(0); IntVariable c2 = y.sign().max(0); IntVariable c3 = z.sign().max(0); // if c1 then c2 else c3 // --> (c1 and c2) or (not c1 and c3) // --> (c1 min c2) max (1-c1 min c3) c1.min(c2).max(c1.negate().add(1).min(c3)).gt(0);

- Can Cream handle soft constraints?
Cream does not support soft constraints directly. However, you can encode them in some cases. Suppose you have a set of soft constraints

`x1<=0, x2<=0, ..., xn<=0`

. They can be expressed in Cream as follows (but, perhaps not efficient).IntVariable w1 = x1.sign().max(0); IntVariable w2 = x2.sign().max(0); ... IntVariable wn = x3.sign().max(0); IntVariable w = w1.add(w2)....add(wn); net.setObjective(w); int opt = Solver.MAXIMIZE | Solver.BETTER; Solver solver = new DefaultSolver(net, opt);

- Is it possible to add constraints dynamically?
Yes, but you need to start a new solver after adding constraints. If you want to find a

*similar*solution after adding constraints, please refer to`neighborhoodSearchExample()`

in Examples.java. - Is it possible to use non-contiguous values for domains?
Yes. The following example declares an integer variable "x" with the domain {1,2,4,8}.

IntDomain d = new IntDomain(1, 7).delete(3).delete(5, 7); IntVariable x = new IntVariable(net, d, "x");

Naoyuki Tamura ( Last modified: Sat May 15 03:06:23 2010 JST , Since Feb 11, 2003 )