Fix benchmark interval count jitter

As the benchmark policy and the interval statistics start at
nearly exactly the same time this could cause the interval statistics
to report one interval too much or not.

This change slightly delays to policy start and suppresses printing
of the last incomplete interval. That way the first interval captures
slightly too little data (but that doesn't matter as it's normally cut
off anyways) and the last incomplete interval only captures data
for the fraction of a second.

src/refit/client/REFITBenchmark.java

@@ -144,6 +144,9 @@ public class REFITBenchmark implements REFITStatisticsListener {
 
 		// Wait for benchmark end
 		statistics.start();
+		// Delay the policy start a bit to make it very likely that the policy completes a short time
+		// after a statistics interval result is printed
+		REFITTime.sleep(79);
 		policy.execute();
 		statistics.end();
 

src/refit/util/REFITIntervalStatistics.java

@@ -27,6 +27,7 @@ public class REFITIntervalStatistics extends Thread {
 	private final WriterReaderPhaser eventPhaser;
 	private final AtomicBoolean firstEvent;
 
+	public int lastEpochCounter;
 	public long overallDurationInUs;
 	public int overallEventCounter;
 	public long overallEventValueAggregation;
@@ -103,7 +104,13 @@ public class REFITIntervalStatistics extends Thread {
 			long myEventValueMax = oldEvent.valueMax.get();
 			eventPhaser.readerUnlock();
 
+			// don't print incomplete last interval
+			if (!running) {
+				break;
+			}
+
 			// update overall counters
+			lastEpochCounter = myResultIndex;
 			overallEventCounter += myEventCount;
 			overallEventValueAggregation += myEventValueAggregation;
 
@@ -154,7 +161,7 @@ public class REFITIntervalStatistics extends Thread {
 		eventPhaser.flipPhase();
 		eventPhaser.readerUnlock();
 
-		listener.statisticsOverallResult(event.epochCounter - 1,
+		listener.statisticsOverallResult(lastEpochCounter,
 				overallEventCounter,
 				overallEventCounter / (float) (overallDurationInUs / (intervalInMs * 1000)),
 				overallEventValueAggregation / (float) overallEventCounter);