Time Resolution
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.Timer;
/*
* TimeResolution.java
*
* Created on May 2, 2007, 3:38 PM
*
* Copyright (c) 2007, Sun Microsystems, Inc
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* * Neither the name of the TimingFramework project nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
*
* @author Chet
*/
public class TimeResolution implements ActionListener {
private static int INCREMENT = 5;
private static int MAX = 50;
/**
* Measures how much time has elapsed according to both currentTimeMillis()
* and nanoTime() at each interval. Note that the time reported for
* sleep() may not be accurate since the internal sleep timer may not
* have the appropriate resolution to sleep for the requested time.
* The main utility of this function is to compare the two timing
* functions, although it is also interesting to see how the measured
* time varies from the sleep() time.
*/
private void measureTimeFunctions(int increment, int max) {
long startTime = System.currentTimeMillis();
long startNanos = System.nanoTime();
long elapsedTimeActual = 0;
long elapsedTimeMeasured = 0;
long elapsedNanosMeasured = 0;
System.out.printf("sleep currentTimeMillis nanoTime\n");
while (elapsedTimeActual < max) {
try {
Thread.sleep(increment);
} catch (Exception e) {}
long currentTime = System.currentTimeMillis();
long currentNanos = System.nanoTime();
elapsedTimeActual += increment;
elapsedTimeMeasured = currentTime - startTime;
elapsedNanosMeasured = (currentNanos - startNanos) / 1000000;
System.out.printf(" %3d %4d %4d\n",
elapsedTimeActual, elapsedTimeMeasured, elapsedNanosMeasured);
}
}
/**
* This method measures the actual time slept, compared to the requested
* sleep() time. We run many iterations for each value of sleep() to
* get more accurate timing values; this accounts for possible
* inaccuracies of our nanoTime() method for small time differences.
*/
private void measureSleep() {
System.out.printf(" measured\n");
System.out.printf("sleep time iterations total time per-sleep\n");
for (int sleepTime = 0; sleepTime <= 20; ++sleepTime) {
int iterations = (sleepTime == 0) ? 10000 : (1000 / sleepTime);
long startTime = System.nanoTime();
for (int i = 0; i < iterations; ++i) {
try {
Thread.sleep(sleepTime);
} catch (Exception e) {
}
}
long endTime = System.nanoTime();
long totalTime = (endTime - startTime) / 1000000;
float calculatedSleepTime = totalTime / (float)iterations;
System.out.printf(" %2d %5d %4d %5.2f\n",
sleepTime, iterations, totalTime, calculatedSleepTime);
}
}
/**
* This method is like the measureSleep() method above, only for the
* wait() method instead of sleep().
*/
private synchronized void measureWait() {
System.out.printf(" measured\n");
System.out.printf("wait time iterations total time per-wait\n");
for (int sleepTime = 1; sleepTime <= 20; ++sleepTime) {
int iterations = (sleepTime == 0) ? 10000 : (1000 / sleepTime);
long startTime = System.nanoTime();
for (int i = 0; i < iterations; ++i) {
try {
wait(sleepTime);
} catch (Exception e) {
System.out.println("Exception: " + e);
Thread.dumpStack();
}
}
long endTime = System.nanoTime();
long totalTime = (endTime - startTime) / 1000000;
float calculatedSleepTime = totalTime / (float)iterations;
System.out.printf(" %2d %5d %4d %5.2f\n",
sleepTime, iterations, totalTime, calculatedSleepTime);
}
}
// Variables used in measurement of Swing timer
int timerIteration = 0;
int iterations = 0;
Timer timer;
long startTime, endTime;
int sleepTime;
/**
* This method is called during the execution of the Swing timer.
*/
public void actionPerformed(ActionEvent ae) {
if (++timerIteration > iterations) {
timer.stop();
timerIteration = 0;
endTime = System.nanoTime();
long totalTime = (endTime - startTime) / 1000000;
float calculatedDelayTime = totalTime / (float)iterations;
System.out.printf(" %2d %5d %5d %5.2f\n",
sleepTime, iterations, totalTime, calculatedDelayTime);
}
}
/**
* This method measures the accuracy of the Swing timer, which is
* internally dependent upon both the internal timing mechanisms
* (either currentTimeMillis() or nanoTime()) and the wait() method.
* So the results we see here should be predictable from the results
* we see in the other measurement methods.
*/
public void measureTimer() {
System.out.printf(" measured\n");
System.out.printf("timer delay iterations total time per-delay\n");
for (sleepTime = 0; sleepTime <= 20; ++sleepTime) {
iterations = (sleepTime == 0) ? 1000 : (1000 / sleepTime);
timerIteration = 1;
timer = new Timer(sleepTime, this);
startTime = System.nanoTime();
timer.start();
while (timerIteration > 0) {
try {
Thread.sleep(1000);
} catch (Exception e) {}
}
}
}
/**
* Execute the various timer resolution tests.
*/
public static void main(String args[]) {
TimeResolution timeResolution = new TimeResolution();
timeResolution.measureTimer();
timeResolution.measureTimeFunctions(INCREMENT, MAX);
timeResolution.measureSleep();
timeResolution.measureWait();
}
}
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