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Introduce offset correction rate

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We want to correct the offset quickly, but we also want to keep the
frequency error caused by the correction itself low.

Define correction rate as the area of the region bounded by the graph of
offset corrected in time. Set the rate so that the time needed to correct
an offset equal to the current sourcestats stddev will be equal to the
update interval (assuming linear adjustment). The offset and the
time needed to make the correction are inversely proportional.

This is only a suggestion and it's up to the system driver how the
adjustment will be executed.
This commit is contained in:
Miroslav Lichvar
2011-09-05 15:45:32 +02:00
parent 79e5f2be13
commit c7d0232bb1
13 changed files with 40 additions and 20 deletions
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7
local.h
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@@ -138,9 +138,10 @@ extern void LCL_AccumulateDeltaFrequency(double dfreq);
/* Routine to apply an offset (in seconds) to the local clock. The
argument should be positive to move the clock backwards (i.e. the
local clock is currently fast of true time), or negative to move it
forwards (i.e. it is currently slow of true time). */
forwards (i.e. it is currently slow of true time). Provided is also
a suggested correction rate (correction time * offset). */
extern void LCL_AccumulateOffset(double offset);
extern void LCL_AccumulateOffset(double offset, double corr_rate);
/* Routine to apply an immediate offset by doing a sudden step if
possible. (Intended for use after an initial estimate of offset has
@@ -158,7 +159,7 @@ extern void LCL_NotifyExternalTimeStep(struct timeval *raw, struct timeval *cook
/* Perform the combination of modifying the frequency and applying
a slew, in one easy step */
extern void LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset);
extern void LCL_AccumulateFrequencyAndOffset(double dfreq, double doffset, double corr_rate);
/* Routine to read the system precision as a log to base 2 value. */
extern int LCL_GetSysPrecisionAsLog(void);