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import org.gnu.glpk.GLPK;
import org.gnu.glpk.GLPKConstants;
import org.gnu.glpk.GlpkCallback;
import org.gnu.glpk.GlpkCallbackListener;
import org.gnu.glpk.GlpkException;
import org.gnu.glpk.SWIGTYPE_p_double;
import org.gnu.glpk.SWIGTYPE_p_int;
import org.gnu.glpk.glp_iocp;
import org.gnu.glpk.glp_prob;
import org.gnu.glpk.glp_tree;
/**
* This example file demonstrates how to safely treat errors when calling the
* glpk library, if the error occurs in the callback function.
*
* It creates a problem and tries to add -1 row in the callback function. This
* will cause an error to occur.
*/
public class ErrorDemo implements GlpkCallbackListener {
static boolean forceError = true;
public void callback(glp_tree tree) {
glp_prob prob;
if (GLPK.glp_ios_reason(tree) == GLPKConstants.GLP_IROWGEN) {
prob = GLPK.glp_ios_get_prob(tree);
if (forceError) {
GLPK.glp_java_set_msg_lvl(GLPKConstants.GLP_JAVA_MSG_LVL_ALL);
try {
GLPK.glp_add_rows(prob, -1);
} catch (GlpkException ex) {
System.out.println("Error in callback: " + ex.getMessage());
}
GLPK.glp_java_set_msg_lvl(GLPKConstants.GLP_JAVA_MSG_LVL_OFF);
}
}
}
/**
* This is the main function.
*/
public static void main(String[] args) {
ErrorDemo d = new ErrorDemo();
System.out.println("GLPK version: " + GLPK.glp_version());
GlpkCallback.addListener(d);
for (int i = 1; i < 5; i++) {
forceError = !forceError;
System.out.print("\nIteration " + i);
if (forceError) {
System.out.println(", error expected to occur.");
} else {
System.out.println(", success expected.");
}
if (d.run()) {
System.out.println("An error has occured.");
if (!forceError) {
System.exit(1);
}
} else {
System.out.println("Successful execution.");
if (forceError) {
System.exit(1);
}
}
}
}
/**
* Build a model with one column
*
* @return error error occurred
*/
private boolean run() {
glp_prob lp;
glp_iocp iocp;
SWIGTYPE_p_int ind;
SWIGTYPE_p_double val;
boolean ret = false;
try {
// Create problem
lp = GLPK.glp_create_prob();
System.out.println("Problem created");
GLPK.glp_set_prob_name(lp, "myProblem");
// Define columns
GLPK.glp_add_cols(lp, 2);
GLPK.glp_set_col_name(lp, 1, "x1");
GLPK.glp_set_col_kind(lp, 1, GLPKConstants.GLP_IV);
GLPK.glp_set_col_bnds(lp, 1, GLPKConstants.GLP_LO, 0, 0);
GLPK.glp_set_col_name(lp, 2, "x2");
GLPK.glp_set_col_kind(lp, 2, GLPKConstants.GLP_IV);
GLPK.glp_set_col_bnds(lp, 2, GLPKConstants.GLP_LO, 0, 0);
// Create constraints
GLPK.glp_add_rows(lp, 2);
GLPK.glp_set_row_name(lp, 1, "c1");
GLPK.glp_set_row_bnds(lp, 1, GLPKConstants.GLP_UP, 0, 40);
ind = GLPK.new_intArray(3);
GLPK.intArray_setitem(ind, 1, 1);
GLPK.intArray_setitem(ind, 2, 2);
val = GLPK.new_doubleArray(3);
GLPK.doubleArray_setitem(val, 1, 10);
GLPK.doubleArray_setitem(val, 2, 7);
GLPK.glp_set_mat_row(lp, 1, 2, ind, val);
GLPK.delete_intArray(ind);
GLPK.delete_doubleArray(val);
ind = GLPK.new_intArray(3);
GLPK.intArray_setitem(ind, 1, 1);
GLPK.intArray_setitem(ind, 2, 2);
val = GLPK.new_doubleArray(3);
GLPK.glp_set_row_name(lp, 2, "c2");
GLPK.glp_set_row_bnds(lp, 2, GLPKConstants.GLP_UP, 0, 5);
GLPK.doubleArray_setitem(val, 1, 1);
GLPK.doubleArray_setitem(val, 2, 1);
GLPK.glp_set_mat_row(lp, 2, 2, ind, val);
GLPK.delete_intArray(ind);
GLPK.delete_doubleArray(val);
// Define objective
GLPK.glp_set_obj_name(lp, "obj");
GLPK.glp_set_obj_dir(lp, GLPKConstants.GLP_MAX);
GLPK.glp_set_obj_coef(lp, 0, 0);
GLPK.glp_set_obj_coef(lp, 1, 17);
GLPK.glp_set_obj_coef(lp, 2, 12);
// solve model
iocp = new glp_iocp();
GLPK.glp_init_iocp(iocp);
iocp.setPresolve(GLPKConstants.GLP_ON);
iocp.setMsg_lev(GLPKConstants.GLP_MSG_OFF);
GLPK.glp_intopt(lp, iocp);
// free memory
GLPK.glp_delete_prob(lp);
} catch (GlpkException ex) {
System.out.println(ex.getMessage());
ret = true;
}
return ret;
}
}
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