SAFETY-136 round 2: tests for override and direction, true wording

F1 the on-change case is tested as slow, F2 override and direction checks,
F3 the 3.75 s rule in the texts, F4 the quarter figures and the live note.
No behaviour change.

Co-Authored-By: Claude <noreply@anthropic.com>

goodwe_controller/DECISIONS/SAFETY-128-late-readings.md

@@ -71,7 +71,8 @@ The fits run all the time; the pull request has the counts.
 **What it costs.**
 - Found 36-68 s after a lag starts at 1-2 s meters; at a 5 s meter 30 s late
   is found within 100 s after it starts (88 s measured) (the loop first moves 100 W after 60 s,
-  SAFETY-129) with the export above -200 W, and 10 s late is not found. Until
+  SAFETY-129) with the export above -200 W, and 10 s late is not found (SAFETY-136 calms
+  the loop at a slow meter instead). Until
   then control is as before. In a quiet house the "readings late" row stays
   about 2 minutes longer after the lag ends (126 s against 32 s on base); no
   harm measured, and it clears as early as on base when the load changes.

goodwe_controller/DECISIONS/SAFETY-136-slow-meter-settle.md

@@ -0,0 +1,81 @@
+# SAFETY-136 - a slow meter gets a gentler loop until the last move shows
+
+**Status: for review.** Code: `app/settle.py`, a call in `Controller.cycle()`
+(`app/ctl_cycle.py`). Tests: `test_safety136.py`. No option, no text change.
+
+**Problem.** On a 5 s meter, Home Assistant readings 10-15 s late are not
+found (SAFETY-129): they look like a slow battery (R2-1), and a hold does not
+help (a perfect one cut the export of the oven by 7 %, SAFETY-129 review).
+With moving loads the loop answers the same stale error at each cycle and
+overshoots: an oven, a kettle and hob, the owner's day or a step export 3-10
+times what they do with no lag. The fix is a calmer loop, not a detector.
+
+**Decision.** After a move of 150 W or more, a loop on a slow meter runs at half
+its gain until the meter has fallen by half of that move, or for 2 cycles.
+Slow is judged from the readings that arrive: the usual gap
+between them, over the last 60 s and at least 5 readings, is over 3.75 s (the
+limit of SAFETY-128's fast meter fit). It counts arrivals, not changes of
+value: on the recorded day at 1-2 s the value-based test (`MeterFit.slow()`)
+called 24 % of the cycles slow, because the recorded house repeats a value
+for 5 s or more, and the commands then differed from base. So there is no
+option. At a meter with a usual gap of 3.75 s or less (1-3 s) it is false, the tuning is never touched and the
+commands are those of the tree before. A meter that Home Assistant passes on
+only when its value changes looks as slow as its changes are far apart, as it
+does to SAFETY-128's fits: a 1-2 s meter with a value that holds for 5 s or
+more is then treated as slow, and the loop is gentler for it (the cost below).
+With no lag the meter shows a move at the next reading, so the wait ends at
+once.
+
+**Candidates** (SAFETY-129 sim, real `cycle()`, 5 s meter, sum over oven,
+kettle and hob, owner shape over the oven and over the heat pump, step down,
+step up, flat; export Wh, lag 0 / 10 s / 15 s; base 64 / 340 / 363):
+
+| Candidate, only at a slow meter | 0 s | 10 s | 15 s | Import Wh, 0 / 10 / 15 s |
+|---|---|---|---|---|
+| gain 0.4 | 97 | 201 | 299 | 97 / 224 / 301 |
+| gain 0.3 | 128 | 185 | 322 | 132 / 232 / 293 |
+| step limit 500 W | 118 | 285 | 293 | 110 / 325 / 324 |
+| cut fast, raise slowly (0.6 / 0.3) | 55 | 140 | 226 | 140 / 332 / 345 |
+| ignore 1 cycle after a move | 93 | 216 | 325 | 90 / 240 / 291 |
+| ignore 2 cycles after a move, unless the meter showed half | 69 | 206 | 277 | 62 / 240 / 354 |
+| **half gain for 2 cycles after a move, unless the meter showed half** | **67** | **189** | **296** | **62 / 223 / 288** |
+
+A lower gain for good, a step limit and a fixed ignore all make a 5 s meter
+with no lag worse (export +30-110 Wh, quarter peak up to 150 W): that is the
+common case. Cutting fast and raising slowly moves export to import and peak.
+Waiting only while the last move has not shown costs nothing with no lag.
+Ignoring the meter (the 2-cycle line) was worse than half gain where the plant
+is slow, not the readings late: a 12 s dead time with one inverter went from
+250 to 841 Wh import and a quarter peak of 206 to 1 509 W, so the loop keeps
+following at half gain.
+
+**What it gives** (5 s meter; the pull request and the report have each
+scenario). Export summed over the seven houses: 10 s late 340 -> 189 Wh
+(-44 %, import 363 -> 223), 15 s late 363 -> 296 Wh (-19 %, import 281 ->
+288), together -31 %. At 15 s the oven and the owner's oven are not better
+(92 / 39 Wh against 91 / 37), the kettle and the steps are. No lag: export
+64.4 -> 66.5 Wh (kettle +2), import and peak the same.
+
+**What it costs.** The loop follows a real step more slowly: half gain for up
+to two cycles after each move of 150 W or more. Of the 136 sim runs (every
+SAFETY-129 review scenario and its 15 harm runs), 56 at 4-10 s meters differ
+from base. Together their export is 10 363 -> 9 559 Wh (-8 %) and import
+8 389 -> 7 835 Wh (-7 %). Only 5 export more than 1 Wh and 14 import more:
+export by at most 11.5 Wh (a 10 s battery lag, +10 %), import by at most
+17 Wh (a 12 s dead time, one inverter, +7 %), and the quarter average by at
+most 35 W, except two import quarters: +73 W (10 s meter, 10 s dead time,
+export -59 Wh) and +40 W (`dead10_p6`, -6 to 34 W, export -68 Wh). Slow
+batteries with a dead time of 8-10 s export 5-39 % less; a 12 s dead time is
+the same. `READINGS_LATE` holds are the same seconds in every run.
+
+**Live, a 1-2 s meter can be judged slow.** Through Home Assistant on change,
+a value that holds for 4-10 s makes a 1 s meter slow. In 20 rig scenarios the
+commands were those of base. On the recorded day (1 s, N=1, 1 day, repeats
+dropped; its values hold about 5 s) it was slow in 33 % of cycles, half gain
+in 83 cycles, 15 422 commands in both trees, 4 016 with another value (at
+most 190 W apart), cost 0.61 EUR in both (review of SAFETY-136).
+
+**Does not change.** Meters of 1-2 s: the same commands in all 63 runs (34
+at 1 s, 29 at 2 s), and the recorded-day digests (see the report). The late
+verdict, the hold and the freeze tests. 15 s late is only partly helped, and
+30 s late is the hold's (SAFETY-129).

goodwe_controller/app/ctl_cycle.py

@@ -734,15 +734,21 @@ class CycleMixin:
             # TEL-10. ⚠️ ONE NAME FOR THE COMMAND THE LOOP WAS MEASURED
             # AGAINST. (DECISIONS/MAIN-orchestration-archive.md)
             loop_prev = self.target
+            # SAFETY-95: a drain's tail is not the loop's to chase.
+            # OPT-15: `loop_grid` is the grid, or the target while a run
+            # edge is held.
+            grid_in = (self._drain_grid_w(_live96) if self._drain_tail
+                       else loop_grid)
+            # SAFETY-136: on a slow meter, a gentler loop until the last move
+            # shows.
+            slow_meter = self.settle.slow()
+            if moved or mode_trade:
+                self.settle.reset()
             decision = compute(
                 prev_w=loop_prev,
-                # SAFETY-95: a drain's tail is not the loop's to chase.
-                # OPT-15: `loop_grid` is the grid, or the target while a run
-                # edge is held.
-                grid_w=(self._drain_grid_w(_live96) if self._drain_tail
-                        else loop_grid),
+                grid_w=grid_in,
                 actual_w=site_batt,
-                tuning=self.tuning,
+                tuning=self.settle.tuning(self.tuning, grid_in, slow_meter),
                 sat_count=self.sat_count,
                 i_w=self.i_w,
                 # SAFETY-52 at one inverter only: with several, OPT-09's pack
@@ -772,6 +778,7 @@ class CycleMixin:
                 self.log_event(f"saturation freeze ({self.target:.0f} W vs "
                                f"{site_batt:.0f} W)",
                                hint=messages.hint("not_keeping_up"))
+            self.settle.moved(grid_in, loop_prev, decision.target_w, slow_meter)
             self.sat_count = decision.sat_count
             self.i_w = decision.i_w
             self.loop_w = decision.target_w
@@ -811,6 +818,7 @@ class CycleMixin:
         else:
             # Stopped or blind: no accumulation may survive the outage.
             self.i_w = 0.0
+            self.settle.reset()
             self.loop_w = None
             self._live_was = frozenset(_live96)
             # TEL-10, and it is the same zero the line above writes rather than

goodwe_controller/app/ctl_inputs.py

@@ -197,6 +197,7 @@ class InputsMixin:
             # correlates 0.998 with battery power and 0.09 with the real meter
             # (a controller would regulate against its own output).
             self.grid = self.p1.net_w
+            self.settle.arrive(now_mono, self.p1.samples)   # SAFETY-136
         else:
             self.grid = await self.hass.number(o.get("meter_entity", ""),
                                                bool(o.get("meter_invert")))

goodwe_controller/app/main.py

@@ -63,6 +63,7 @@ from .clamp import (
 )
 from . import freshness
 from . import lateness
+from .settle import Settle
 from . import dayview, homeview
 from .daycurve import SolarToday
 from . import handback
@@ -741,6 +742,7 @@ class Controller(InputsMixin, WritesMixin, TradeMixin, CycleMixin, AlarmsMixin,
         self._arb_action = None
         self.inputs_bad_since = None
         self.answer = lateness.Answer()           # SAFETY-128
+        self.settle = Settle()                    # SAFETY-136
         self._late_logged = self._late_zero = False
         # SAFETY-03: what the loop's OWN bounds did last cycle, `(engaged,
         # note, over_rating)` (SAFETY-40 splits the last out). Site-level: the

goodwe_controller/app/settle.py

@@ -0,0 +1,74 @@
+"""SAFETY-136: on a slow meter, follow the meter gently until the last move shows.
+
+A meter whose usual gap between readings is over 3.75 s (a 4-5 s meter), read
+through Home Assistant, can be 10-15 s late. The loop then answers the same error again at each cycle
+and overshoots. After a move of MOVE_W or more the loop therefore runs at
+WAIT_SHARE of its gain until the meter has fallen SHOWN of the move, or for at
+most WAIT_CYCLES cycles. Off for a meter with a usual gap of 3.75 s or less, so those sites run as
+before. DECISIONS/SAFETY-136-slow-meter-settle.md.
+"""
+
+from collections import deque
+from dataclasses import replace
+
+from .lateness import M_FIT_S, M_ROWS
+
+# A meter is slow when its readings come further apart than this (the usual
+# gap, over the last 60 s and at least 5 readings): the fast meter fit's own
+# limit (SAFETY-128), 3.75 s.
+SLOW_GAP_S = M_FIT_S / M_ROWS
+SLOW_ROWS = 5
+# A move this big is waited for (above the house noise of about 80 W).
+MOVE_W = 150.0
+# The meter has shown a move once it fell by this share of it.
+SHOWN = 0.5
+# Meanwhile the loop runs at this share of its gain.
+WAIT_SHARE = 0.5
+# Wait at most this many cycles (10 s at a 5 s meter).
+WAIT_CYCLES = 2
+
+
+class Settle:
+    def __init__(self):
+        self.pend = None          # (meter at the move, the move in W, cycles waited)
+        self._n = None            # readings taken in so far
+        self._at = deque()        # when the last ones arrived, over M_FIT_S
+
+    def arrive(self, now, n):
+        """Each read: `n` is the count of meter readings taken in. A reading
+        counts when it arrives, not when its value changes, so a steady load on
+        a 1 s meter is not a slow meter."""
+        if n != self._n:
+            self._n = n
+            self._at.append(now)
+        while self._at and self._at[0] < now - M_FIT_S:
+            self._at.popleft()
+
+    def slow(self):
+        """The usual gap between readings is over SLOW_GAP_S."""
+        ts = list(self._at)
+        if len(ts) < SLOW_ROWS:
+            return False
+        gaps = sorted(b - a for a, b in zip(ts, ts[1:]))
+        return gaps[len(gaps) // 2] > SLOW_GAP_S
+
+    def reset(self):
+        self.pend = None
+
+    def tuning(self, tuning, grid_w, slow):
+        """The tuning for this cycle: `tuning`, or with the gain cut while the
+        last move has not shown on the meter (`grid_w`)."""
+        p = self.pend
+        if p is None:
+            return tuning
+        g0, move, waited = p
+        if not slow or (g0 - grid_w) / move >= SHOWN or waited >= WAIT_CYCLES:
+            self.pend = None
+            return tuning
+        self.pend = (g0, move, waited + 1)
+        return replace(tuning, gain=tuning.gain * WAIT_SHARE)
+
+    def moved(self, grid_w, prev_w, new_w, slow):
+        """After a cycle: start waiting if the loop moved by MOVE_W or more."""
+        if slow and self.pend is None and abs(new_w - prev_w) >= MOVE_W:
+            self.pend = (float(grid_w), float(new_w - prev_w), 0)

goodwe_controller/test_safety129.py

@@ -38,6 +38,7 @@ logging.disable(logging.WARNING)
 import safety128_rig as R                                      # noqa: E402
 import app.main as app_main                                    # noqa: E402
 from app import lateness                                       # noqa: E402
+from app import settle                                         # noqa: E402
 
 fails = []
 
@@ -58,6 +59,17 @@ def no_gate(fn):
         app_main.Controller._readings_late = real
 
 
+def no_settle(fn):
+    """`fn()` without SAFETY-136's gentler loop: the tree this card was written
+    against (with it the same run exports -645 W, not -1 325 W)."""
+    real = settle.Settle.moved
+    settle.Settle.moved = lambda self, *a, **k: None
+    try:
+        return fn()
+    finally:
+        settle.Settle.moved = real
+
+
 def run_late(**kw):
     """Run the rig; (rig, seconds the verdict stood, first second it stood)."""
     dur = kw.pop("dur")
@@ -91,7 +103,7 @@ for units, house in ((AB, 1800.0), (A, 1500.0)):
     if len(units) == 2:
         old = R.Rig(house=house, lag_s=30.0, lag_on=ON, lag_off=ON + 300.0,
                     units=units, p1_s=5.0)
-        no_gate(lambda: old.run(ON + 300.0))
+        no_settle(lambda: no_gate(lambda: old.run(ON + 300.0)))
         check(f"{n}: without the gate the export goes below -1 kW",
               grid_min(old.rows, ON, ON + 300.0) < -1000.0)
 

goodwe_controller/test_safety136.py

@@ -0,0 +1,263 @@
+"""Runnable check for SAFETY-136: a calmer loop on a slow meter.
+`python3 test_safety136.py`
+
+With a 5 s meter and Home Assistant readings 10-15 s late the loop answers the
+same error again at each cycle and overshoots: with an oven, a kettle and hob,
+or a step the export was 3-10 times that of a meter with no lag. After a move
+of 150 W or more `app/settle.py` now runs the loop at half its gain (at most
+2 cycles) until the meter shows half of it. It is off for a meter under 4 s.
+DECISIONS/SAFETY-136-slow-meter-settle.md.
+
+The REAL Controller on TEST-23's plant (tools/safety128_rig.py). "Off" is the
+same run with `Settle.moved` doing nothing: the tree before this card.
+
+1. `Settle` alone.
+2. 5 s meter, readings 10 s late: oven, kettle and hob, a step down and a step
+   up export clearly less than with it off.
+3. 5 s meter, no lag: the same houses are no worse than a small margin.
+4. 1 s and 2 s meters: the commands are those of the run with it off, and the
+   loop never waits.
+5. The slow meter is told by its observed interval, at 4 s and 5 s.
+
+Mutations (MUTATION.md, purged copies) are listed in the pull request.
+"""
+
+import logging
+import os
+import sys
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, HERE)
+sys.path.insert(0, os.path.join(HERE, "tools"))
+logging.disable(logging.WARNING)
+
+import safety128_rig as R                                      # noqa: E402
+from app.control import Tuning                                # noqa: E402
+from named_absence import nth, present                         # noqa: E402
+from app import settle                                         # noqa: E402
+from app.lateness import MeterFit                              # noqa: E402
+
+fails = []
+
+
+def check(name, cond):
+    print(f"  {'ok  ' if cond else 'FAIL'} {name}")
+    if not cond:
+        fails.append(name)
+
+
+def off(fn):
+    """`fn()` with the settle wait off: the tree before this card."""
+    real = settle.Settle.moved
+    settle.Settle.moved = lambda self, *a, **k: None
+    try:
+        return fn()
+    finally:
+        settle.Settle.moved = real
+
+
+def oven(t):
+    return 1800.0 + (2000.0 if (t >= 300.0 and (t - 300.0) % 105 < 45) else 0.0)
+
+
+def kettle(t):
+    w = 600.0
+    if t % 400 < 120:
+        w += 2200
+    if t >= 900 and t % 90 < 30:
+        w += 1500
+    return w
+
+
+def step(t):
+    return 1800.0 if t < 320.0 else 300.0
+
+
+def stepup(t):
+    return 300.0 if t < 320.0 else 2500.0
+
+
+# name: (house, noise, run length, lag end)
+HOUSES = {"oven": (oven, 80.0, 900.0, 900.0),
+          "kettle": (kettle, 80.0, 1500.0, 1500.0),
+          "step": (step, 50.0, 700.0, 600.0),
+          "stepup": (stepup, 50.0, 700.0, 600.0)}
+ON = 300.0
+
+
+def wh(rows, t0, t1, sign):
+    """Export (sign -1) or import (sign +1) energy in Wh over [t0, t1)."""
+    return sum((-min(r[1], 0.0) if sign < 0 else max(r[1], 0.0))
+               for r in rows if t0 <= r[0] < t1) / 3600.0
+
+
+def run(name, lag, p1_s=5.0, units=("a", "b"), dur=None):
+    house, noise, length, lag_off = HOUSES[name]
+    r = R.Rig(house=house, noise=noise, p1_s=p1_s, units=units, lag_s=lag,
+              lag_on=ON, lag_off=lag_off)
+    waits = []
+    r.run(dur or length + 20.0,
+          lambda rig, c, t: waits.append(1) if c.settle.pend else None)
+    return r, len(waits)
+
+
+# --------------------------------------------------------------------------- #
+print("1. Settle alone")
+T = Tuning()
+s = settle.Settle()
+check("no move: the tuning is untouched", s.tuning(T, 500.0, True) is T)
+s.moved(500.0, 0.0, 100.0, True)
+check("a move under 150 W is not waited for", s.pend is None)
+s.moved(500.0, 0.0, 600.0, False)
+check("a meter that is not slow is not waited for", s.pend is None)
+s.moved(500.0, 0.0, 600.0, True)
+check("a move of 600 W is waited for: half the gain",
+      s.tuning(T, 500.0, True).gain == T.gain * 0.5)
+check("the meter fell 200 W of 600 W: still half the gain",
+      s.tuning(T, 300.0, True).gain == T.gain * 0.5)
+check("two cycles waited: the third has the whole gain",
+      s.tuning(T, 300.0, True) is T and s.pend is None)
+s.moved(500.0, 0.0, 600.0, True)
+check("the meter went the other way by half the move: the wait stands",
+      s.tuning(T, 800.0, True).gain == T.gain * 0.5)
+s.reset()
+s.moved(500.0, 0.0, -600.0, True)
+check("a move down, the meter rose half the move: the whole gain",
+      s.tuning(T, 800.0, True) is T)
+s.reset()
+s.moved(500.0, 0.0, 600.0, True)
+check("the meter fell half the move: the whole gain at once",
+      s.tuning(T, 200.0, True) is T and s.pend is None)
+s.moved(500.0, 0.0, -600.0, True)
+check("a move down is waited for too",
+      s.tuning(T, 500.0, True).gain == T.gain * 0.5)
+s.reset()
+check("reset ends the wait", s.pend is None)
+s.moved(500.0, 0.0, 600.0, True)
+check("a meter that turns out not to be slow ends the wait",
+      s.tuning(T, 500.0, False) is T and s.pend is None)
+check("the numbers are pinned",
+      (settle.MOVE_W, settle.SHOWN, settle.WAIT_SHARE, settle.WAIT_CYCLES)
+      == (150.0, 0.5, 0.5, 2))
+
+# --------------------------------------------------------------------------- #
+print("\n2. 5 s meter, readings 10 s late")
+tot_on = tot_off = 0.0
+for name, (_h, _n, length, lag_off) in HOUSES.items():
+    a, waited = run(name, 10.0)
+    b, _w = off(lambda: run(name, 10.0))
+    ea, eb = wh(a.rows, ON, lag_off, -1), wh(b.rows, ON, lag_off, -1)
+    tot_on, tot_off = tot_on + ea, tot_off + eb
+    print(f"    {name}: export {ea:.1f} Wh, off {eb:.1f} Wh, waited {waited} s")
+    check(f"{name}: waits at some point", waited > 0)
+    check(f"{name}: exports at most 75 % of the run with it off",
+          ea <= 0.75 * eb)
+print(f"    sum: {tot_on:.1f} Wh, off {tot_off:.1f} Wh")
+check("the four together export at most 65 % of the run with it off",
+      tot_on <= 0.65 * tot_off)
+
+# --------------------------------------------------------------------------- #
+print("\n2b. Another writer overrides the loop: the wait ends")
+halved = []
+real_tuning = settle.Settle.tuning
+
+
+def watch_tuning(self, tuning, grid_w, slow):
+    r = real_tuning(self, tuning, grid_w, slow)
+    halved.append(r is not tuning)
+    return r
+
+
+settle.Settle.tuning = watch_tuning
+try:
+    mark = []
+
+    def bump(rig, c, t):
+        # right after a cycle that started a wait, another writer moves the
+        # command, so the next cycle sees `target != loop_w`
+        if not mark and c.settle.pend and t > 330.0:
+            mark.append(len(halved))
+            c.target = c.target + 300.0
+
+    r = R.Rig(house=oven, noise=80.0, p1_s=5.0, lag_s=10.0, lag_on=ON,
+              lag_off=900.0)
+    r.run(500.0, bump)
+finally:
+    settle.Settle.tuning = real_tuning
+nxt = nth(halved, mark[0] if mark else 10 ** 6)
+check("the cycle after an override has the whole gain",
+      bool(mark) and present(nxt) and nxt is False)
+
+# --------------------------------------------------------------------------- #
+print("\n3. 5 s meter, no lag")
+for name in ("oven", "kettle", "step", "stepup"):
+    _h, _n, length, lag_off = HOUSES[name]
+    a, _w = run(name, 0.0)
+    b, _w = off(lambda: run(name, 0.0))
+    ea, eb = wh(a.rows, ON, lag_off, -1), wh(b.rows, ON, lag_off, -1)
+    ia, ib = wh(a.rows, ON, lag_off, 1), wh(b.rows, ON, lag_off, 1)
+    print(f"    {name}: export {ea:.1f} Wh (off {eb:.1f}), import {ia:.1f} Wh "
+          f"(off {ib:.1f})")
+    check(f"{name}: export at most 6 Wh over the run with it off",
+          ea <= eb + 6.0)
+    check(f"{name}: import at most 1 Wh over the run with it off",
+          ia <= ib + 1.0)
+
+# --------------------------------------------------------------------------- #
+print("\n4. 1 s and 2 s meters")
+for p1 in (1.0, 2.0):
+    for lag in (0.0, 10.0):
+        for units in (("a", "b"), ("a",)):
+            a, waited = run("oven", lag, p1_s=p1, units=units, dur=700.0)
+            b, _w = off(lambda: run("oven", lag, p1_s=p1, units=units,
+                                    dur=700.0))
+            same = ([(r[0], r[1], r[2]) for r in a.rows]
+                    == [(r[0], r[1], r[2]) for r in b.rows])
+            check(f"{p1:.0f} s meter, {lag:.0f} s late, N={len(units)}: "
+                  f"same commands, never waits", same and waited == 0)
+
+# --------------------------------------------------------------------------- #
+print("\n5. The slow meter is told by its observed interval")
+s = settle.Settle()
+for k in range(30):
+    s.arrive(float(k), k)
+check("a reading each second is not a slow meter", not s.slow())
+s = settle.Settle()
+for k in range(30):
+    s.arrive(5.0 * k, k)
+check("a reading every 5 s is a slow meter", s.slow())
+s = settle.Settle()
+for k in range(4):
+    s.arrive(5.0 * k, k)
+check("fewer than 5 readings in a minute tell nothing", not s.slow())
+s = settle.Settle()
+for k in range(30):
+    s.arrive(5.0 * k, 0 if k else 1)
+check("the same count again is no new reading", not s.slow())
+for p1, expect in ((1.0, False), (2.0, False), (3.0, False), (4.0, True),
+                   (5.0, True), (10.0, True)):
+    r = R.Rig(house=1800.0, p1_s=p1)
+    seen = []
+    r.run(120.0, lambda rig, c, t: seen.append(c.settle.slow()))
+    last = nth(seen, -1)
+    check(f"{p1:.0f} s meter: slow is {expect}",
+          present(last) and last is expect)
+# A 1 s meter on a house that changes every 5 s repeats its value 4 times in 5.
+# Where every reading arrives (the rig, a polled meter) it is not slow; where
+# Home Assistant sends a reading only when the value changes (ha_signed) the
+# same meter is slow (T3 of the review; DECISIONS).
+s, m, h = settle.Settle(), MeterFit(), settle.Settle()
+for k in range(60):
+    s.arrive(float(k), k)
+    h.arrive(float(k), k // 5)
+    m.add(float(k), 0.0, 1800.0 + 100.0 * (k // 5))
+check("every reading arrives, value changes every 5 s: not slow (the value "
+      "fit says slow)", not s.slow() and m.slow())
+check("the same meter through Home Assistant on change (a reading per "
+      "change): slow", h.slow())
+
+print()
+if fails:
+    print(f"{len(fails)} FAILED: " + ", ".join(fails))
+    sys.exit(1)
+print("all checks passed")