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Go back to using the median value for our delta estimate.

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git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@3991 542714f4-19e9-0310-aa3c-eee0fc999fb1
This commit is contained in:
Ray Greenwell
2006-03-30 19:06:40 +00:00
parent 981deb3b6b
commit fb913a6bba
1 changed files with 29 additions and 18 deletions
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src/java/com/threerings/presents/client/DeltaCalculator.java
+29 -18
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@@ -106,26 +106,37 @@ public class DeltaCalculator
return 0L; return 0L;
} }
if (true) { // Return a median value as our estimate, rather than an average.
// return the mean // Mdb writes:
long est = 0; // -----------
for (int ii=0; ii < _iter; ii++) { // I used the median because that was more likely to result in a
est += _deltas[ii]; // sensible value.
} //
return (est / _iter); // Assuming there are two kinds of packets, one that goes and comes
// back without delay and provides an accurate time value, and one
// that gets delayed somewhere on the way there or the way back and
// provides an inaccurate time value.
//
// If no packets are delayed, both algorithms should be fine. If one
// packet is delayed the median will select the middle, non-delayed
// packet, whereas the average will skew everything a bit because
// of the delayed packet. If two packets are delayed, the median
// will be more skewed than the average because it will benefit
// from the one accurate packet and if all three packets are delayed
// both algorithms will be (approximately) equally inaccurate.
//
// I believe the chances are most likely that zero or one packets
// will be delayed, so I chose the median rather than the average.
// -----------
} else { // copy the deltas array so that we don't alter things before
// return the median value // all pongs have arrived
long[] deltasCopy = new long[_iter];
System.arraycopy(_deltas, 0, deltasCopy, 0, _iter);
// copy the deltas array so that we don't alter things before // sort the estimates and return one from the middle
// all pongs have arrived Arrays.sort(deltasCopy);
long[] deltasCopy = new long[_iter]; return deltasCopy[deltasCopy.length/2];
System.arraycopy(_deltas, 0, deltasCopy, 0, _iter);
// sort the estimates and return one from the middle
Arrays.sort(deltasCopy);
return deltasCopy[deltasCopy.length/2];
}
} }
/** /**