IBM Power7 Optimization And Tuning Manual page 195

static int Num=1000;
public static void main(String[] args) {
o = new Object();
new ProfileTest().start(); /* start 3 threads */
new ProfileTest().start(); /* each thread executes the "run" method */
new ProfileTest().start();
}
public void run() {
double sum = 0.0;
for (int i = 0; i < 50000; i++) {
sum += doWork(); /* repeatedly do some work */
}
System.out.println("sum: "+sum); /* use the results of the work */
}
public double doWork() {
double d;
synchronized (o) { /* serialize the threads to create lock contention */
A = new Double [Num];
B = new Double [Num];
C = new Double [Num];
initialize();
calculate();
d = C[0].doubleValue();
}
return(d); /* use the calculated values */
}
public static void initialize() {
/* Initialize A and B. */
for (int i = 0; i < Num; i++) {
A[i] = new Double(Math.random()); /* use new to create objects */
B[i] = new Double(Math.random()); /* to force garbage collection */
}
}
public static void calculate() {
for (int i = 0; i < Num; i++) {
C[i] = new Double(A[i].doubleValue() * B[i].doubleValue());
}
}
}
The program also uses the Double class, creating many short-lived objects by using new. By
running the program with a small Java heap, GC frequently is required to free the Java heap
space that is taken by the Double objects that are no longer in use.
Appendix B. Performance tooling and empirical performance analysis
179