/*
* This file is part of the Jikes RVM project (http://jikesrvm.org).
*
* This file is licensed to You under the Eclipse Public License (EPL);
* You may not use this file except in compliance with the License. You
* may obtain a copy of the License at
*
* http://www.opensource.org/licenses/eclipse-1.0.php
*
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership.
*/
package org.jikesrvm.adaptive.measurements.listeners;
import org.jikesrvm.VM;
import org.jikesrvm.scheduler.RVMThread;
import org.vmmagic.pragma.Uninterruptible;
/**
* A simple listener to accumulate counts of total events
* and the fraction of those events that occurred at loop backedges.
* In effect, this provides a mechanism for estimating the
* call density of the program. If most yieldpoints are being taken at
* backedges, then call density is low.
*/
@Uninterruptible
public final class CallDensityListener extends NullListener {
private double numSamples = 0;
private double numBackedgeSamples = 0;
@Override
public void update(int whereFrom) {
numSamples++;
if (whereFrom == RVMThread.BACKEDGE) numBackedgeSamples++;
}
public double callDensity() {
return 1 - (numBackedgeSamples / numSamples);
}
@Override
public void reset() {
numSamples = 0;
numBackedgeSamples = 0;
}
@Override
public void report() {
VM.sysWriteln("The call density of the program is ", callDensity());
}
}