Mip2.java
*/ /*这个例子从一个文件中读取一个狗万app足彩MIP模型，求解它，并从求解MIP时产生的所有可行的解决方案中打印客观值。然后它创建固定模型并求解该模型。* /进口gurobi。*;public class Mip2 {public static void main(String[] args);length < 1) {System.out. length = 1;println(“使用:java Mip2文件名”);system . exit (1);} try {GRBEnv env = new GRBEnv();/ /创建GRBModel = env, args， [0];if (model.get(GRB.IntAttr.IsMIP) == 0) {System.out. ismip == 0;println(“模型不是一个MIP”);system . exit (1); } model.optimize(); int optimstatus = model.get(GRB.IntAttr.Status); double objval = 0; if (optimstatus == GRB.Status.OPTIMAL) { objval = model.get(GRB.DoubleAttr.ObjVal); System.out.println("Optimal objective: " + objval); } else if (optimstatus == GRB.Status.INF_OR_UNBD) { System.out.println("Model is infeasible or unbounded"); return; } else if (optimstatus == GRB.Status.INFEASIBLE) { System.out.println("Model is infeasible"); return; } else if (optimstatus == GRB.Status.UNBOUNDED) { System.out.println("Model is unbounded"); return; } else { System.out.println("Optimization was stopped with status = " + optimstatus); return; } /* Iterate over the solutions and compute the objectives */ model.set(GRB.IntParam.OutputFlag, 0); System.out.println(); for (int k = 0; k < model.get(GRB.IntAttr.SolCount); ++k) { model.set(GRB.IntParam.SolutionNumber, k); double objn = model.get(GRB.DoubleAttr.PoolObjVal); System.out.println("Solution " + k + " has objective: " + objn); } System.out.println(); model.set(GRB.IntParam.OutputFlag, 1); /* Create a fixed model, turn off presolve and solve */ GRBModel fixed = model.fixedModel(); fixed.set(GRB.IntParam.Presolve, 0); fixed.optimize(); int foptimstatus = fixed.get(GRB.IntAttr.Status); if (foptimstatus != GRB.Status.OPTIMAL) { System.err.println("Error: fixed model isn't optimal"); return; } double fobjval = fixed.get(GRB.DoubleAttr.ObjVal); if (Math.abs(fobjval - objval) > 1.0e-6 * (1.0 + Math.abs(objval))) { System.err.println("Error: objective values are different"); return; } GRBVar[] fvars = fixed.getVars(); double[] x = fixed.get(GRB.DoubleAttr.X, fvars); String[] vnames = fixed.get(GRB.StringAttr.VarName, fvars); for (int j = 0; j < fvars.length; j++) { if (x[j] != 0.0) { System.out.println(vnames[j] + " " + x[j]); } } // Dispose of models and environment fixed.dispose(); model.dispose(); env.dispose(); } catch (GRBException e) { System.out.println("Error code: " + e.getErrorCode() + ". " + e.getMessage()); } } }
