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sourcestats: include precision in weight calculation

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In order to stabilize the weights of refclock samples which have only
slightly different distances, don't allow the stddev value used in the
weight calculation to be smaller than the precision and also assign
weight of 1 to all samples which have distance < minimum + precision.
This commit is contained in:
Miroslav Lichvar 2017-06-21 17:48:26 +02:00
parent cc507bffae
commit 7fb7f95979
1 changed files with 8 additions and 6 deletions
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14
sourcestats.c
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@ -51,9 +51,6 @@
#define MIN_SKEW 1.0e-12
#define MAX_SKEW 1.0e+02
/* The minimum assumed std dev for weighting */
#define MIN_WEIGHT_SD 1.0e-9
/* The asymmetry of network jitter when all jitter is in one direction */
#define MAX_ASYMMETRY 0.5
@ -489,6 +486,7 @@ SST_DoNewRegression(SST_Stats inst)
double min_distance, mean_distance;
double sd_weight, sd;
double old_skew, old_freq, stress;
double precision;
convert_to_intervals(inst, times_back + inst->runs_samples);
@ -510,11 +508,15 @@ SST_DoNewRegression(SST_Stats inst)
/* And now, work out the weight vector */
sd = mean_distance - min_distance;
sd = CLAMP(MIN_WEIGHT_SD, sd, min_distance);
precision = LCL_GetSysPrecisionAsQuantum();
sd = (mean_distance - min_distance) / SD_TO_DIST_RATIO;
sd = CLAMP(precision, sd, min_distance);
min_distance += precision;
for (i=0; i<inst->n_samples; i++) {
sd_weight = 1.0 + SD_TO_DIST_RATIO * (peer_distances[i] - min_distance) / sd;
sd_weight = 1.0;
if (peer_distances[i] > min_distance)
sd_weight += (peer_distances[i] - min_distance) / sd;
weights[i] = sd_weight * sd_weight;
}
}