lpmod_c + + . cpp
/* This example rea狗万app足彩d an LP model from a file and solve it. /* This example read an LP model from a file and solve it。如果模型可以求解，则找到最小的正变量，将其上限设为零，并采用两种方法求解模型:先采用高级启动，再采用不采用高级启动(即先采用高级启动)。“从头开始”)。*/ #include "gurobi_c++.h" using namespace std;int main(int argc, char *argv[]) {if (argc < 2) {cout << "Usage: lpmod_c++ filename" << endl;返回1;} GRBEnv* env = 0;GRBVar* v = 0;try{//读取模型并确定它是否是一个LP env = new GRBEnv();GRBModel model = GRBModel(*env, argv[1]); if (model.get(GRB_IntAttr_IsMIP) != 0) { cout << "The model is not a linear program" << endl; return 1; } model.optimize(); int status = model.get(GRB_IntAttr_Status); if ((status == GRB_INF_OR_UNBD) || (status == GRB_INFEASIBLE) || (status == GRB_UNBOUNDED)) { cout << "The model cannot be solved because it is " << "infeasible or unbounded" << endl; return 1; } if (status != GRB_OPTIMAL) { cout << "Optimization was stopped with status " << status << endl; return 0; } // Find the smallest variable value double minVal = GRB_INFINITY; int minVar = 0; v = model.getVars(); for (int j = 0; j < model.get(GRB_IntAttr_NumVars); ++j) { double sol = v[j].get(GRB_DoubleAttr_X); if ((sol > 0.0001) && (sol < minVal) && (v[j].get(GRB_DoubleAttr_LB) == 0.0)) { minVal = sol; minVar = j; } } cout << "\n*** Setting " << v[minVar].get(GRB_StringAttr_VarName) << " from " << minVal << " to zero ***" << endl << endl; v[minVar].set(GRB_DoubleAttr_UB, 0.0); // Solve from this starting point model.optimize(); // Save iteration & time info double warmCount = model.get(GRB_DoubleAttr_IterCount); double warmTime = model.get(GRB_DoubleAttr_Runtime); // Reset the model and resolve cout << "\n*** Resetting and solving " << "without an advanced start ***\n" << endl; model.reset(); model.optimize(); // Save iteration & time info double coldCount = model.get(GRB_DoubleAttr_IterCount); double coldTime = model.get(GRB_DoubleAttr_Runtime); cout << "\n*** Warm start: " << warmCount << " iterations, " << warmTime << " seconds" << endl; cout << "*** Cold start: " << coldCount << " iterations, " << coldTime << " seconds" << endl; } catch (GRBException e) { cout << "Error code = " << e.getErrorCode() << endl; cout << e.getMessage() << endl; } catch (...) { cout << "Error during optimization" << endl; } delete[] v; delete env; return 0; }
