Example mip1_c.c
This is the complete source code for our example (also available as
<installdir>/examples/c/mip1_c.c)...
#include <stdlib.h>
#include <stdio.h>
#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;
int zero = 0;
/* Create environment */
error = GRBloadenv(&env, "mip1.log");
if (error || env == NULL) {
fprintf(stderr, "Error: could not create environment\n");
exit(1);
}
/* 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, NULL);
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, NULL);
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;
}
