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## Cloud Guide

qp_c.c

### qp_c.c

```/* Copyright 2018, Gurobi Optimization, LLC */

/* This example formulates and solves the following simple QP model:

minimize    x^2 + x*y + y^2 + y*z + z^2 + 2 x
subject to  x + 2 y + 3 z >= 4
x +   y       >= 1

It solves it once as a continuous model, and once as an integer model.
*/

#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];
int       qrow[5];
int       qcol[5];
double    qval[5];
char      vtype[3];
int       optimstatus;
double    objval;

/* Create environment */

if (error) goto QUIT;

/* Create an empty model */

error = GRBnewmodel(env, &model, "qp", 0, NULL, NULL, NULL, NULL, NULL);
if (error) goto QUIT;

error = GRBaddvars(model, 3, 0, NULL, NULL, NULL, NULL, NULL, NULL, NULL,
NULL);
if (error) goto QUIT;

qrow[0] = 0; qrow[1] = 0; qrow[2] = 1; qrow[3] = 1; qrow[4] = 2;
qcol[0] = 0; qcol[1] = 1; qcol[2] = 1; qcol[3] = 2; qcol[4] = 2;
qval[0] = 1; qval[1] = 1; qval[2] = 1; qval[3] = 1; qval[4] = 1;

error = GRBaddqpterms(model, 5, qrow, qcol, qval);
if (error) goto QUIT;

/* Linear objective term */

error = GRBsetdblattrelement(model, GRB_DBL_ATTR_OBJ, 0, 2.0);
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_GREATER_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 'qp.lp' */

error = GRBwrite(model, "qp.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=%.4f, y=%.4f, z=%.4f\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");
}

/* Modify variable types */

vtype[0] = GRB_INTEGER; vtype[1] = GRB_INTEGER; vtype[2] = GRB_INTEGER;

error = GRBsetcharattrarray(model, GRB_CHAR_ATTR_VTYPE, 0, 3, vtype);
if (error) goto QUIT;

/* Optimize model */

error = GRBoptimize(model);
if (error) goto QUIT;

/* Write model to 'qp2.lp' */

error = GRBwrite(model, "qp2.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=%.4f, y=%.4f, z=%.4f\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;
}
```