Java Thread Performance: AtomicTest
/*
Java Threads, 3rd Edition
By Scott Oaks, Henry Wong
3rd Edition September 2004
ISBN: 0-596-00782-5
*/
import java.util.*;
import java.util.concurrent.*;
import java.util.concurrent.atomic.*;
public class AtomicTest {
static int nLoops;
static int nThreads;
public static void main(String[] args) {
nLoops = 10000;
nThreads = 1;
doTest(new AtomicRunnable());
doTest(new SyncRunnable());
nLoops = Integer.parseInt(args[0]);
nThreads = Integer.parseInt(args[1]);
System.out.println("Starting atomic test");
cleanGC();
Timestamp atomicTS = new Timestamp();
doTest(new AtomicRunnable());
atomicTS.stop();
System.out.println("Atomic took " + atomicTS);
System.out.println("Starting sync test");
cleanGC();
Timestamp syncTS = new Timestamp();
doTest(new SyncRunnable());
syncTS.stop();
System.out.println("Local sync took " + syncTS);
double d = ((double) (syncTS.elapsedTime() - atomicTS.elapsedTime()))
/ (nLoops * nThreads);
System.out.println("Atomic operation saves " + d + " " + syncTS.units()
+ " per call");
}
static void cleanGC() {
System.gc();
System.runFinalization();
System.gc();
}
static class AtomicRunnable implements Runnable {
AtomicInteger ai = new AtomicInteger(1);
public void run() {
for (int i = 0; i < nLoops; i++)
ai.incrementAndGet();
}
}
static class SyncRunnable implements Runnable {
int testVar;
synchronized void incrVar() {
testVar++;
}
public void run() {
for (int i = 0; i < nLoops; i++)
incrVar();
}
}
static void doTest(Runnable r) {
Thread threads[] = new Thread[nThreads];
for (int i = 0; i < nThreads; i++) {
threads[i] = new Thread(r);
}
for (int i = 0; i < nThreads; i++) {
threads[i].start();
}
for (int i = 0; i < nThreads; i++) {
try {
threads[i].join();
} catch (InterruptedException ie) {
}
}
}
}
class Timestamp {
private long startTime;
private long stopTime;
private boolean stopped = false;
private TimeUnit ts;
public Timestamp() {
this(TimeUnit.NANOSECONDS);
}
public Timestamp(TimeUnit ts) {
this.ts = ts;
start();
}
public void start() {
startTime = System.nanoTime();
stopped = false;
}
public void stop() {
stopTime = System.nanoTime();
stopped = true;
}
public long elapsedTime() {
if (!stopped)
throw new IllegalStateException("Timestamp not stopped");
return ts.convert(stopTime - startTime, TimeUnit.NANOSECONDS);
}
public String toString() {
try {
return elapsedTime() + " " + ts;
} catch (IllegalStateException ise) {
return "Timestamp (not stopped)";
}
}
public String units() {
return ts.toString();
}
}
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