"long" Multiply and Assignment: 38 Nanoseconds per Step

This section provides a tutorial example on how to perform benchmark tests to find out how long a multiply and assignment loop will take to run. The answer is 38 nanoseconds per step.

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

```/**
* BenchmarkTestLong.java
*/
class BenchmarkTestLong {
...
// Test method for a multiply operation in a loop
public static long multiply(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
BanchmarkTestLong multiply 10000 100 10
...
Runs: 100, Ave: 276, Min: 251, Max: 279 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestLong multiply 10000 100 100
...
Runs: 100, Ave: 61, Min: 59, Max: 64 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestLong multiply 10000 100 1000
...
Runs: 100, Ave: 40, Min: 40, Max: 41 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestLong multiply 10000 100 10000
...
Runs: 100, Ave: 38, Min: 38, Max: 44 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestLong multiply 10000 100 100000
...
Runs: 100, Ave: 38, Min: 38, Max: 38 - Per step in nanoseconds

C:\herong\jvm>java -Xint -Xms100m -Xmx100m BenchmarkRunner
BanchmarkTestLong multiply 10000 100 1000000
...
Runs: 100, Ave: 38, Min: 38, Max: 40 - Per step in nanoseconds
```

Conclusions based on the test result:

• The loop runs 38 nanoseconds per step with a multiply operation in the assignment statement.
• Clearly, the execution time of a multiplication operation, i*3, is about 14 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: 38 - 24 = 14 nanoseconds.

Last update: 2010.