mip1_c.c
/* Copyright 2021, Gurobi Optimization, LLC */ /* This example formulates and solves the following simple MIP model: maximize x + y + 2 z subject to x + 2 y + 3 z <= 4 x + y >= 1 x, y, z binary */ #include #include #include "gurobi_c.h" int main(int argc, char *argv[]) { GRBenv *env = NULL; GRBmodel *model = NULL; int error = 0; double sol[3]; int ind[3]; double val[3]; double obj[3]; char vtype[3]; int optimstatus; double objval; /* Create environment */ error = GRBemptyenv(&env); if (error) goto QUIT; error = GRBsetstrparam(env, "LogFile", "mip1.log"); if (error) goto QUIT; error = GRBstartenv(env); if (error) goto QUIT; /* Create an empty model */ error = GRBnewmodel(env, &model, "mip1", 0, NULL, NULL, NULL, NULL, NULL); if (error) goto QUIT; /* Add variables */ obj[0] = 1; obj[1] = 1; obj[2] = 2; vtype[0] = GRB_BINARY; vtype[1] = GRB_BINARY; vtype[2] = GRB_BINARY; error = GRBaddvars(model, 3, 0, NULL, NULL, NULL, obj, NULL, NULL, vtype, NULL); if (error) goto QUIT; /* Change objective sense to maximization */ error = GRBsetintattr(model, GRB_INT_ATTR_MODELSENSE, GRB_MAXIMIZE); if (error) goto QUIT; /* First constraint: x + 2 y + 3 z <= 4 */ ind[0] = 0; ind[1] = 1; ind[2] = 2; val[0] = 1; val[1] = 2; val[2] = 3; error = GRBaddconstr(model, 3, ind, val, GRB_LESS_EQUAL, 4.0, "c0"); if (error) goto QUIT; /* Second constraint: x + y >= 1 */ ind[0] = 0; ind[1] = 1; val[0] = 1; val[1] = 1; error = GRBaddconstr(model, 2, ind, val, GRB_GREATER_EQUAL, 1.0, "c1"); if (error) goto QUIT; /* Optimize model */ error = GRBoptimize(model); if (error) goto QUIT; /* Write model to 'mip1.lp' */ error = GRBwrite(model, "mip1.lp"); if (error) goto QUIT; /* Capture solution information */ error = GRBgetintattr(model, GRB_INT_ATTR_STATUS, &optimstatus); if (error) goto QUIT; error = GRBgetdblattr(model, GRB_DBL_ATTR_OBJVAL, &objval); if (error) goto QUIT; error = GRBgetdblattrarray(model, GRB_DBL_ATTR_X, 0, 3, sol); if (error) goto QUIT; printf("\nOptimization complete\n"); if (optimstatus == GRB_OPTIMAL) { printf("Optimal objective: %.4e\n", objval); printf(" x=%.0f, y=%.0f, z=%.0f\n", sol[0], sol[1], sol[2]); } else if (optimstatus == GRB_INF_OR_UNBD) { printf("Model is infeasible or unbounded\n"); } else { printf("Optimization was stopped early\n"); } QUIT: /* Error reporting */ if (error) { printf("ERROR: %s\n", GRBgeterrormsg(env)); exit(1); } /* Free model */ GRBfreemodel(model); /* Free environment */ GRBfreeenv(env); return 0; }
