Change Output Stream

[Martin Fuchsberger]

Dear colleagues,

I was wondering if there is a possibility to change the default screen
output in the GUROBI JAVA API by passing an output stream as a
parameter to the gurobi environment instance.

I realized from the documentation that you can change the logfile, but
I was not able to find a way on changing the output console.

Cplex provides this as follows:

OutputStream outputStream = ...;

cplex = new IloCplex();
cplex.setOut(outputStream);

Since I migrate from cplex to gurobi, I hope a similar functionality
is available which I don't know yet.

Any help is greatly appreciated!

Sincerly,

Martin Fuchsberger

[Victor Pillac]

Hi Martin,

Have you tried System.setOut()? (http://download.oracle.com/javase/
1.4.2/docs/api/java/lang/System.html#setOut(java.io.PrintStream))
You can redirect to a custom stream that prints in a file and in the
console.

Regards

On Nov 2, 10:06 am, Martin Fuchsberger <fumar...@ifor.math.ethz.ch>
wrote:

[Greg Glockner]

Alternately, you can create an informational callback that captures the logfile information and uses it however you want. See Callback.java in the examples\java subdirectory.

[Martin Fuchsberger]

Hi Victor,

I actually use System.setOut in another class which is basically a
console window with a text area as part of an application (See below).
But Gurobi is not directly affected by that as well as cplex. That's
why I passed cplex.setOut() the outputStream of that class, which
worked well.

Maybe I miss the obvious solution here?

<code>

import java.awt.BorderLayout;
import java.awt.Point;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.PrintStream;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class Console extends JFrame {
class ReaderThread extends Thread {
PipedInputStream pi;

ReaderThread(final PipedInputStream pi) {
this.pi = pi;
}

@Override
public void run() {
final byte[] buf = new byte[1024];
try {
while (true) {
final int len = pi.read(buf);
if (len == -1) {
break;
}
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
textArea.append(new String(buf, 0, len));

// Make sure the last line is always visible
textArea.setCaretPosition(textArea.getDocument().getLength());

// Keep the text area down to a certain character
// size
final int idealSize = 1000;
final int maxExcess = 500;
final int excess = textArea.getDocument().getLength() -
idealSize;
if (excess >= maxExcess) {
textArea.replaceRange("", 0, excess);
}
}
});
}
} catch (final IOException e) {
}
}
}

PipedInputStream piOut;
PipedInputStream piErr;
PipedOutputStream poOut;
PipedOutputStream poErr;

JTextArea textArea = new JTextArea();

public Console(final int xPos, final int yPos) throws IOException {
// Set up System.out
piOut = new PipedInputStream();
poOut = new PipedOutputStream(piOut);
System.setOut(new PrintStream(poOut, true));

// Set up System.err
piErr = new PipedInputStream();
poErr = new PipedOutputStream(piErr);
System.setErr(new PrintStream(poErr, true));

// Add a scrolling text area
textArea.setEditable(false);
textArea.setRows(20);
textArea.setColumns(130);

getContentPane().add(new JScrollPane(textArea),
BorderLayout.CENTER);
pack();
setLocation(new Point(xPos, yPos));
setVisible(true);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create reader threads
new ReaderThread(piOut).start();
new ReaderThread(piErr).start();
}

public OutputStream getOutputStream() {
return poOut;
}
}

</code>

[Martin Fuchsberger]

Agreed, that is a possible solution. Is there a specific reason why
you can't redirect the console output stream of gurobi?

[Greg Glockner]

If you want an even simpler approach, just turn off the console logging and use the log file.