Added examples/knapsack.py to illustrate setSolution in highspy

examples/knapsack.py

@@ -0,0 +1,55 @@
+import numpy as np
+import highspy
+
+h = highspy.Highs()
+h.setOptionValue("output_flag", False);
+h.setOptionValue("presolve", "off");
+inf = highspy.kHighsInf
+lp = highspy.HighsLp()
+lp.sense_ = highspy.ObjSense.kMaximize
+lp.num_col_ = 5
+lp.num_row_ = 1
+lp.col_cost_ = np.array([8, 5, 3, 11, 7], dtype=np.double)
+lp.col_lower_ = np.array([0, 0, 0, 0, 0], dtype=np.double)
+lp.col_upper_ = np.array([1, 1, 1, 1, 1], dtype=np.double)
+lp.row_lower_ = np.array([-inf], dtype=np.double)
+lp.row_upper_ = np.array([11], dtype=np.double)
+lp.a_matrix_.format_ = highspy.MatrixFormat.kRowwise
+lp.a_matrix_.start_ = np.array([0, 5])
+lp.a_matrix_.index_ = np.array([0, 1, 2, 3, 4])
+lp.a_matrix_.value_ = np.array([4, 3, 1, 5, 4], dtype=np.double)
+lp.integrality_ = np.array([highspy.HighsVarType.kInteger, highspy.HighsVarType.kInteger, highspy.HighsVarType.kInteger, highspy.HighsVarType.kInteger, highspy.HighsVarType.kInteger])
+h.passModel(lp)
+
+h.run()
+solution = h.getSolution()
+print(f"Solution: ({solution.col_value[0]}, {solution.col_value[1]}, {solution.col_value[2]}, {solution.col_value[3]}, {solution.col_value[4]})")
+
+# Solution is [1, 0, 1, 1, 0]
+
+# Illustrate setSolution
+
+# First by passing back the optimal solution
+
+h.clearSolver()
+h.setSolution(solution)
+h.run()
+solution = h.getSolution()
+print(f"Solution: ({solution.col_value[0]}, {solution.col_value[1]}, {solution.col_value[2]}, {solution.col_value[3]}, {solution.col_value[4]})")
+
+# Now passing back the optimal values of two variables as a sparse solution
+h.clearSolver()
+index = np.array([0, 3])
+value = np.array([1, 1], dtype=np.double)
+h.setSolution(2, index, value)
+h.run()
+solution = h.getSolution()
+print(f"Solution: ({solution.col_value[0]}, {solution.col_value[1]}, {solution.col_value[2]}, {solution.col_value[3]}, {solution.col_value[4]})")
+
+# Test passing back the optimal value of one variable, and a non-optimal value of another, as a sparse solution in untyped array
+h.clearSolver()
+h.setSolution(2, np.array([0, 4]), np.array([1, 1]))
+h.run()
+solution = h.getSolution()
+print(f"Solution: ({solution.col_value[0]}, {solution.col_value[1]}, {solution.col_value[2]}, {solution.col_value[3]}, {solution.col_value[4]})")
+