I've a requirement to capture the execution time of some code in iterations. I've decided to use a Map<Integer,Long> for capturing this data where Integer(key) is the iteration number and Long(value) is the time consumed by that iteration in milliseconds.
I've written the below java code to compute the time taken for each iteration. I want to ensure that the time taken by all iterations is zero before invoking actual code. Surprisingly, the below code behaves differently for every execution.
Sometimes, I get the desired output(zero millisecond for all iterations), but at times I do get positive and even negative values for some random iterations.
I've tried replacing System.currentTimeMillis(); with below code:
new java.util.Date().getTime();
System.nanoTime();
org.apache.commons.lang.time.StopWatch
but still no luck.
Any suggestions as why some iterations take additional time and how to eliminate it?
package com.stackoverflow.programmer;
import java.util.HashMap;
import java.util.Map;
public class TestTimeConsumption {
public static void main(String[] args) {
Integer totalIterations = 100000;
Integer nonZeroMilliSecondsCounter = 0;
Map<Integer, Long> timeTakenMap = new HashMap<>();
for (Integer iteration = 1; iteration <= totalIterations; iteration++) {
timeTakenMap.put(iteration, getTimeConsumed(iteration));
if (timeTakenMap.get(iteration) != 0) {
nonZeroMilliSecondsCounter++;
System.out.format("Iteration %6d has taken %d millisecond(s).\n", iteration,
timeTakenMap.get(iteration));
}
}
System.out.format("Total non zero entries : %d", nonZeroMilliSecondsCounter);
}
private static Long getTimeConsumed(Integer iteration) {
long startTime = System.currentTimeMillis();
// Execute code for which execution time needs to be captured
long endTime = System.currentTimeMillis();
return (endTime - startTime);
}
}
Here's the sample output from 5 different executions of the same code:
Execution #1 (NOT OK)
Iteration 42970 has taken 1 millisecond(s).
Total non zero entries : 1
Execution #2 (OK)
Total non zero entries : 0
Execution #3 (OK)
Total non zero entries : 0
Execution #4 (NOT OK)
Iteration 65769 has taken -1 millisecond(s).
Total non zero entries : 1
Execution #5 (NOT OK)
Iteration 424 has taken 1 millisecond(s).
Iteration 33053 has taken 1 millisecond(s).
Iteration 76755 has taken -1 millisecond(s).
Total non zero entries : 3
I am looking for a Java based solution that ensures that all iterations consume zero milliseconds consistently. I prefer to accomplish this using pure Java code without using a profiler.
Note: I was also able to accomplish this through C code.
