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sourcestats: add fixed asymmetry

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Rework the code to allow the jitter asymmetry to be specified.
This commit is contained in:
Miroslav Lichvar
2017-08-22 16:26:40 +02:00
parent d0964ffa83
commit b06d74ab73
7 changed files with 59 additions and 32 deletions
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68
sourcestats.c
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@@ -85,6 +85,9 @@ struct SST_Stats_Record {
/* User defined minimum delay */
double fixed_min_delay;
/* User defined asymmetry of network jitter */
double fixed_asymmetry;
/* Number of samples currently stored. The samples are stored in circular
buffer. */
int n_samples;
@@ -200,7 +203,8 @@ 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, double min_delay)
SST_CreateInstance(uint32_t refid, IPAddr *addr, int min_samples, int max_samples,
double min_delay, double asymmetry)
{
SST_Stats inst;
inst = MallocNew(struct SST_Stats_Record);
@@ -208,6 +212,7 @@ SST_CreateInstance(uint32_t refid, IPAddr *addr, int min_samples, int max_sample
inst->min_samples = min_samples;
inst->max_samples = max_samples;
inst->fixed_min_delay = min_delay;
inst->fixed_asymmetry = asymmetry;
SST_SetRefid(inst, refid, addr);
SST_ResetInstance(inst);
@@ -422,14 +427,43 @@ find_min_delay_sample(SST_Stats inst)
minimum network delay. This can significantly improve the accuracy and
stability of the estimated offset and frequency. */
static int
estimate_asymmetry(double *times_back, double *offsets, double *delays, int n,
double *asymmetry, int *asymmetry_run)
{
double a;
/* Reset the counter when the regression fails or the sign changes */
if (!RGR_MultipleRegress(times_back, delays, offsets, n, &a) ||
a * *asymmetry_run < 0.0) {
*asymmetry = 0;
*asymmetry_run = 0.0;
return 0;
}
if (a <= -MIN_ASYMMETRY && *asymmetry_run > -MAX_ASYMMETRY_RUN)
(*asymmetry_run)--;
else if (a >= MIN_ASYMMETRY && *asymmetry_run < MAX_ASYMMETRY_RUN)
(*asymmetry_run)++;
if (abs(*asymmetry_run) < MIN_ASYMMETRY_RUN)
return 0;
*asymmetry = CLAMP(-MAX_ASYMMETRY, a, MAX_ASYMMETRY);
return 1;
}
/* ================================================== */
static void
correct_asymmetry(SST_Stats inst, double *times_back, double *offsets)
{
double asymmetry, min_delay, delays[MAX_SAMPLES * REGRESS_RUNS_RATIO];
double 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)
/* Check if the asymmetry was not specified to be zero */
if (inst->fixed_asymmetry == 0.0)
return;
min_delay = SST_MinRoundTripDelay(inst);
@@ -439,29 +473,17 @@ correct_asymmetry(SST_Stats inst, double *times_back, double *offsets)
delays[i] = inst->peer_delays[get_runsbuf_index(inst, i - inst->runs_samples)] -
min_delay;
/* Reset the counter when the regression fails or the sign changes */
if (!RGR_MultipleRegress(times_back, delays, offsets, n, &asymmetry) ||
asymmetry * inst->asymmetry_run < 0.0) {
inst->asymmetry_run = 0;
inst->asymmetry = 0.0;
return;
if (fabs(inst->fixed_asymmetry) <= MAX_ASYMMETRY) {
inst->asymmetry = inst->fixed_asymmetry;
} else {
if (!estimate_asymmetry(times_back, offsets, delays, n,
&inst->asymmetry, &inst->asymmetry_run))
return;
}
asymmetry = CLAMP(-MAX_ASYMMETRY, asymmetry, MAX_ASYMMETRY);
if (asymmetry <= -MIN_ASYMMETRY && inst->asymmetry_run > -MAX_ASYMMETRY_RUN)
inst->asymmetry_run--;
else if (asymmetry >= MIN_ASYMMETRY && inst->asymmetry_run < MAX_ASYMMETRY_RUN)
inst->asymmetry_run++;
if (abs(inst->asymmetry_run) < MIN_ASYMMETRY_RUN)
return;
/* Correct the offsets */
for (i = 0; i < n; i++)
offsets[i] -= asymmetry * delays[i];
inst->asymmetry = asymmetry;
offsets[i] -= inst->asymmetry * delays[i];
}
/* ================================================== */