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sourcestats: add fixed minimum delay

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If the minimum delay is known (in a static network configuration), it
can replace the measured minimum from the register. This should improve
the stability of corrections for asymmetric jitter, sample weighting and
maxdelay* tests.
This commit is contained in:
Miroslav Lichvar
2017-08-17 16:44:18 +02:00
parent 3d08815efb
commit d0964ffa83
7 changed files with 26 additions and 10 deletions
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18
sourcestats.c
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@@ -82,6 +82,9 @@ struct SST_Stats_Record {
int min_samples;
int max_samples;
/* User defined minimum delay */
double fixed_min_delay;
/* Number of samples currently stored. The samples are stored in circular
buffer. */
int n_samples;
@@ -197,13 +200,14 @@ SST_Finalise(void)
/* This function creates a new instance of the statistics handler */
SST_Stats
SST_CreateInstance(uint32_t refid, IPAddr *addr, int min_samples, int max_samples)
SST_CreateInstance(uint32_t refid, IPAddr *addr, int min_samples, int max_samples, double min_delay)
{
SST_Stats inst;
inst = MallocNew(struct SST_Stats_Record);
inst->min_samples = min_samples;
inst->max_samples = max_samples;
inst->fixed_min_delay = min_delay;
SST_SetRefid(inst, refid, addr);
SST_ResetInstance(inst);
@@ -310,6 +314,9 @@ SST_AccumulateSample(SST_Stats inst, struct timespec *sample_time,
inst->root_dispersions[m] = root_dispersion;
inst->strata[m] = stratum;
if (inst->peer_delays[n] < inst->fixed_min_delay)
inst->peer_delays[n] = 2.0 * inst->fixed_min_delay - inst->peer_delays[n];
if (!inst->n_samples || inst->peer_delays[n] < inst->peer_delays[inst->min_delay_sample])
inst->min_delay_sample = n;
@@ -418,18 +425,19 @@ find_min_delay_sample(SST_Stats inst)
static void
correct_asymmetry(SST_Stats inst, double *times_back, double *offsets)
{
double asymmetry, delays[MAX_SAMPLES * REGRESS_RUNS_RATIO];
double asymmetry, min_delay, delays[MAX_SAMPLES * REGRESS_RUNS_RATIO];
int i, n;
/* Don't try to estimate the asymmetry with reference clocks */
if (!inst->ip_addr)
return;
min_delay = SST_MinRoundTripDelay(inst);
n = inst->runs_samples + inst->n_samples;
for (i = 0; i < n; i++)
delays[i] = inst->peer_delays[get_runsbuf_index(inst, i - inst->runs_samples)] -
inst->peer_delays[inst->min_delay_sample];
min_delay;
/* Reset the counter when the regression fails or the sign changes */
if (!RGR_MultipleRegress(times_back, delays, offsets, n, &asymmetry) ||
@@ -771,8 +779,12 @@ SST_PredictOffset(SST_Stats inst, struct timespec *when)
double
SST_MinRoundTripDelay(SST_Stats inst)
{
if (inst->fixed_min_delay > 0.0)
return inst->fixed_min_delay;
if (!inst->n_samples)
return DBL_MAX;
return inst->peer_delays[inst->min_delay_sample];
}