added sol09.txt

exercises/ex09/solutions/sol09.txt

+|------------------|
+| Solution of ex09 |
+|------------------|
+
+
+---
+9.1
+---
+
+CPLEX
+
+conv1i.mod: qp hessian is not positive-semidefinite
+
+conv2i.mod: qp hessian is not positive-semidefinite
+
+linearize constraint:
+conv3i.mod: solution (-2,3)
+it is already using the option rqconvex=3 (global solution)
+
+conv4i.mod: identical to conv3i.mod
+
+
+
+---
+9.2
+---
+
+Gurobi
+
+conv5i.mod: Gurobi hangs, it makes millions of iterations and when stopped it returns (-2,-2)
+BUG ???
+
+
+
+---
+9.3
+---
+
+Xpress
+
+conv6i.mod: it works fine, returninig the solution (-2,3)
+
+
+
+---
+9.4
+---
+
+SCIP
+
+conv7i.mod: it works fine, returning the solution (-2,3)
+
+original quadratic constraint
+conv8i.mod: it works fine, returning the solution (0,1)
+
+non-convex constraint
+conv9i.mod: it works fine, returning the solution (0,1)
+
+
+
+---
+9.5
+---
+
+See boiler.mod.
+The problem is not-convex (try to plot the objective)
+
+
+
+
+---
+9.6
+---
+
+See boiler_int1.mod and boiler_int2.mod
+KNITRO without multistart will return a local solution for the boiler_int2.mod
+KNITRO with multistart finds the global solution (same as Couenne)
+