Stable32 TimeLab allantools

Stable32, TimeLab and allantools

ntpstats is meant to sit next to the tools time-and-frequency people already use. This page shows how to move data and code between them, and what to expect when you compare results.

Stable32

Stable32 reads plain ASCII columns: values, optionally with an MJD timetag first, plus header or comment lines, which it skips. ntpstats reads and writes the same layout.

# any supported log (chrony, ntpd, linuxptp, pcap, CSV...) -> Stable32 phase file with MJD timetags
ntpstats convert /var/log/chrony/tracking.log -o tracking.dat
# fractional-frequency file instead, values only
ntpstats convert tracking.log -o tracking-freq.dat --to stable32-freq --no-timetags

# and back: analyse a Stable32 data file
ntpstats stability data.dat -f stable32-phase -k oadev,mdev,mtot
ntpstats stability freq.dat -f stable32-freq --tau0 1 -k oadev,hdev,ttot

from ntpstats.interop import read_stable32, write_stable32

s = read_stable32("freq.dat", data_type="freq", tau0=1.0)   # integrated to phase
write_stable32(s, "phase.dat", data_type="phase")

Conventions:

• Phase is in seconds, and frequency is fractional (dimensionless).
• Zero frequency values are gaps, as in Stable32.
• A phase gap is written as a missing timetag.

Comparing numbers. ADEV, OADEV, MDEV, TDEV, HDEV, TOTDEV, MTOT and TTOT reproduce the NIST SP 1065 test suites (which come from Stable32) to 7 digits; see Validation. MTOT and TTOT include Stable32's noise-type bias correction. Use --raw-mtot (CLI) or bias_correction=False (API) for the uncorrected eq. (27) value. Confidence intervals can differ: for ADEV-family statistics ntpstats computes the EDF exactly for the discrete noise model, where Stable32 uses published approximations.

TimeLab

TimeLab's native .tim format is not publicly documented, so ntpstats does not read it yet. To move data into TimeLab, export plain phase or frequency columns (ntpstats convert ... --no-timetags). If you can share a small .tim file, please attach it to issue #33.

allantools

ntpstats.compat.allantools has the allantools call signatures, so existing scripts switch with one import:

# import allantools as at
from ntpstats.compat import allantools as at

taus, devs, errs, ns = at.oadev(y, rate=1.0, data_type="freq", taus="octave")
taus, devs, errs, ns = at.mdev(x, rate=10.0, taus=[0.1, 1, 10])

Available functions:

• adev, oadev, mdev, tdev;
• hdev (non-overlapping) and ohdev;
• totdev, mtotdev, ttotdev;
• theo1, mtie, tierms;
• frequency2phase and phase2frequency.

The values match allantools to 1e-9 on the frozen comparison table in the tests. There are three differences:

• mtotdev and ttotdev stay raw, as in allantools, while stability.compute bias-corrects them.
• theo1 returns the effective τ = 0.75·m/rate.
• htotdev is not implemented yet.

For confidence intervals, noise identification and gap handling, use the native API:

from ntpstats import stability

r = stability.compute(x, tau0=1.0, kind="oadev", taus="octave", ci=0.683)
r.taus, r.dev, r.lo, r.hi, r.edf, r.alpha