params_c.c
/* Copyright 2021, 狗万app足彩Gurobi Optimization, LLC */ /*使用与模型相关的参数。用不同的参数集求解一个MIP，只需几秒钟。选择MIP间隙最小的那个，继续优化，直到找到最优解。*/ #include #include #include #include "gurobi_c.h" int main(int argc, char *argv[]) {GRBenv *env = NULL， *modelenv = NULL， *bestenv = NULL;GRBmodel *model = NULL， *bestmodel = NULL;Int error = 0;Int ismip, i, mipfocus;双bestgap差距;if (argc < 2) {fprintf(stderr， "Usage: params_c filename\n");退出(1); } error = GRBloadenv(&env, "params.log"); if (error) goto QUIT; /* Read model and verify that it is a MIP */ error = GRBreadmodel(env, argv[1], &model); if (error) goto QUIT; error = GRBgetintattr(model, "IsMIP", &ismip); if (error) goto QUIT; if (ismip == 0) { printf("The model is not an integer program\n"); exit(1); } /* Set a 2 second time limit */ modelenv = GRBgetenv(model); if (!modelenv) { printf("Cannot retrieve model environment\n"); exit(1); } error = GRBsetdblparam(modelenv, "TimeLimit", 2); if (error) goto QUIT; /* Now solve the model with different values of MIPFocus */ bestmodel = GRBcopymodel(model); if (!bestmodel) { printf("Cannot copy model\n"); exit(1); } error = GRBoptimize(bestmodel); if (error) goto QUIT; error = GRBgetdblattr(bestmodel, "MIPGap", &bestgap); if (error) goto QUIT; for (i = 1; i <= 3; ++i) { error = GRBreset(model, 0); if (error) goto QUIT; modelenv = GRBgetenv(model); if (!modelenv) { printf("Cannot retrieve model environment\n"); exit(1); } error = GRBsetintparam(modelenv, "MIPFocus", i); if (error) goto QUIT; error = GRBoptimize(model); if (error) goto QUIT; error = GRBgetdblattr(model, "MIPGap", &gap); if (error) goto QUIT; if (bestgap > gap) { GRBmodel *tmp = bestmodel; bestmodel = model; model = tmp; bestgap = gap; } } /* Finally, free the extra model, reset the time limit and continue to solve the best model to optimality */ GRBfreemodel(model); bestenv = GRBgetenv(bestmodel); if (!bestenv) { printf("Cannot retrieve best model environment\n"); exit(1); } error = GRBsetdblparam(bestenv, "TimeLimit", GRB_INFINITY); if (error) goto QUIT; error = GRBoptimize(bestmodel); if (error) goto QUIT; error = GRBgetintparam(bestenv, "MIPFocus", &mipfocus); if (error) goto QUIT; printf("Solved with MIPFocus: %i\n", mipfocus); QUIT: /* Error reporting */ if (error) { printf("ERROR: %s\n", GRBgeterrormsg(env)); exit(1); } /* Free best model */ GRBfreemodel(bestmodel); /* Free environment */ GRBfreeenv(env); return 0; }
