"long" Division and Assignment: 53 Nanoseconds per Step

This section provides a tutorial example on how to perform benchmark tests to find out how long a division and assignment loop will take to run. The answer is 53 nanoseconds per step.

The next test is to measure the division operation performance. Here is the test method:

```/**
* BenchmarkTestLong.java
*/
class BenchmarkTestLong {
...
// Test method for a division operation in a loop
public static long division(int steps, BenchmarkRunner runner) {
long x = 0;
long i = 0;
long last = steps;
runner.startTimer();
for (i=0; i<last; i++) {
x = i/3;
}
runner.stopTimer();
return x;
}
}
```

Here are test results:

```C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestInt division 10000 100 10
...
Runs: 100, Ave: 285, Min: 251, Max: 335 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestInt division 10000 100 100
...
Runs: 100, Ave: 73, Min: 70, Max: 75 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestInt division 10000 100 1000
...
Runs: 100, Ave: 52, Min: 52, Max: 53 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestInt division 10000 100 10000
...
Runs: 100, Ave: 50, Min: 50, Max: 51 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestInt division 10000 100 100000
...
Runs: 100, Ave: 51, Min: 51, Max: 54 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestInt division 10000 100 1000000
...
Runs: 100, Ave: 53, Min: 52, Max: 55 - Per step in nanoseconds
```

Conclusions based on the test result:

• The loop runs 53 nanoseconds per step with an division operation in the assignment statement.
• The execution time of a division operation, i/3, is about 29 nanoseconds in interpreted-only mode. This conclusion can be arrived from test results of 10000, 100000 and 1000000 steps and minus the assignment loop execution time: 53 - 24 = 29 nanoseconds.

Last update: 2010.