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import org.gnu.glpk.*;
public class Gmpl implements GlpkCallbackListener, GlpkTerminalListener {
private boolean hookUsed = false;
public static void main(String[] arg) {
if (1 != arg.length) {
System.out.println("Usage: java Gmpl model.mod");
return;
}
GLPK.glp_java_set_numeric_locale("C");
new Gmpl().solve(arg);
}
public void solve(String[] arg) {
glp_prob lp = null;
glp_tran tran = null;
glp_iocp iocp;
String fname;
int skip = 0;
int ret;
// listen to callbacks
GlpkCallback.addListener(this);
// listen to terminal output
GlpkTerminal.addListener(this);
try {
// create problem
lp = GLPK.glp_create_prob();
// allocate workspace
tran = GLPK.glp_mpl_alloc_wksp();
// read model
fname = arg[0];
ret = GLPK.glp_mpl_read_model(tran, fname, skip);
if (ret != 0) {
GLPK.glp_mpl_free_wksp(tran);
GLPK.glp_delete_prob(lp);
throw new RuntimeException("Model file not valid: "
+ fname);
}
// generate model
ret = GLPK.glp_mpl_generate(tran, null);
if (ret != 0) {
GLPK.glp_mpl_free_wksp(tran);
GLPK.glp_delete_prob(lp);
throw new RuntimeException("Cannot generate model: "
+ fname);
}
// build model
GLPK.glp_mpl_build_prob(tran, lp);
// set solver parameters
iocp = new glp_iocp();
GLPK.glp_init_iocp(iocp);
iocp.setPresolve(GLPKConstants.GLP_ON);
// do not listen to output anymore
GlpkTerminal.removeListener(this);
// solve model
ret = GLPK.glp_intopt(lp, iocp);
// postsolve model
if (ret == 0) {
GLPK.glp_mpl_postsolve(tran, lp,
GLPKConstants.GLP_MIP);
}
// free memory
GLPK.glp_mpl_free_wksp(tran);
GLPK.glp_delete_prob(lp);
} catch (RuntimeException e) {
System.err.println("An exeption of class "
+ e.getClass() + " occured.");
System.err.println(e.getMessage());
}
// do not listen for callbacks anymore
GlpkCallback.removeListener(this);
// check that the terinal hook function has been used
if (!hookUsed) {
throw new RuntimeException(
"The terminal output hook was not used.");
}
}
@Override
public boolean output(String str) {
hookUsed = true;
System.out.print(str);
return false;
}
@Override
public void callback(glp_tree tree) {
int reason = GLPK.glp_ios_reason(tree);
if (reason == GLPKConstants.GLP_IBINGO) {
System.out.println("Better solution found");
}
}
}
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