The tail rescale shipped in cd392e7 is a measured NULL as a search
intervention -- 12 of 12 pairs byte-identical on harbor and maple, 8000 evals
from a plateau, not merely underpowered. Of course it is: the whole failing
tail is 0.034% of corpus value. Looking at the rest of the factor, prompted by
the owner, found something much larger above the threshold.
crink = area_outside/area = (L*h)/A, so 1/crink = A/(L*h) is the room's mean
depth from its daylit wall in storey-heights. That is the right variable for a
daylight rule, and the fail boundary it implies (1/crink = 1.62, i.e. 4.86 m at
h=3) is a sensible one that agrees with 38.3's frontage bound derived
independently. What is wrong is hanging a TWO-sided gaussian on it:
* The near side penalises a room for having MORE daylit wall than target --
while leaf_cost's siblings edge_cost and outside_edge_cost already charge
that same wall at exterior_wall=100 and boundary_wall=133.3 per m2. The wall
is billed once in cost and again as lost value.
* It never earns its keep as a failure either: the over-exposed branch only
reaches FAIL_THRESHOLD above crinkliness 21.5, and the corpus maximum is
3.95. It has never produced a single fail; it only removes value.
* 133 of the 318 passing graded leaves in the 500k baseline (42%) sit on that
side, mean quality 0.810.
crinkliness_shape="daylight" (default OFF, "gaussian" is stock) clips it: a
room shallower than the gaussian's peak scores 1.0, because daylight is a
sufficiency requirement and surplus is the cost model's business, not this
factor's. Clipping at the PEAK rather than at FAIL_THRESHOLD is deliberate --
it keeps the factor continuous and preserves the graded approach to the
daylight limit, where clipping at the threshold would put a 10x cliff on the
exact boundary the 0.5**n fail multiplier already steps on.
Fail set byte-identical on all 21 corpus artefacts for all four
shape/tail combinations, so stock stays a valid yardstick for every arm.
Area-weighted crinkliness quality 0.480 -> 0.513, leaf quality product
0.2722 -> 0.2831; per-artefact score +0.2%..+19.6%, and unlike the ramp it
reaches health-centre and programme-house, where the tail change was 0.000%.
Note "daylight" clips the OPPOSITE side from 38.1's superseded compact_ok,
which forgives being buried; composing either with those modes is refused.
ab_9gj_ramp.py becomes ab_9gj_crinkliness.py and takes named arms, since it
now covers both changes; its first arm is the baseline and the yardstick.
Refs homemaker-py-9gj.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MJ84Feep79Hhm3E4zZJmnB
quality_uncrinkliness evaluates a gaussian at x = 1/crink, so its exponent
grows like 1/crink^2 and underflows a double to exactly zero below crink ~
1/15. Measured over the twelve 500k cold-start runs (39.12): 430 leaves carry
a minimum-exposure requirement, 112 fail it, and those 112 span quality
1e-300..1e-1 while contributing 0.034% of total value on 23% of the floor
area. Every value in that range is numerically zero beside a passing leaf's
~1, so the search cannot rank two layouts that differ only in how exposed
their under-lit rooms are.
This is wider than the bead's diagnosis (a flat 0.0 for zero-exposure leaves)
and it explains why 38.1's `floor` mode measured as a no-op: max(q, 0.01) maps
110 of the 112 onto one constant, replacing a flat zero with a flat 0.01.
crinkliness_tail="ramp" (default OFF, "gaussian" is stock) replaces the tail --
only the tail, only below FAIL_THRESHOLD, only on the compact side -- with a
straight line in crinkliness meeting the gaussian exactly at the crossing.
_crink_at_fail_threshold inverts the gaussian there using the same truncated
_E the factor is evaluated with.
Deliberately conservative: nothing at or above FAIL_THRESHOLD moves, so no
calibration changes and no leaf crosses the threshold. The fail set is
byte-identical on all 21 committed corpus artefacts, the four init.dom seeds
included -- asserted in tests/test_fitness_crinkliness_tail.py, not assumed.
That invariance is also what makes it legal to score both arms of the A/B
under stock (the 38.9 trap's one exemption). A fully buried leaf still scores
exactly 0; this restores an ordering within the failing region, it does not
forgive it. Composing with 38.1's superseded modes is refused, since both
rewrite the same tail.
Score effect on the baseline artefacts: +0.3%..+2.8% on harbor and maple,
exactly +0.000% on health-centre, programme-house, and every init.dom -- a
programme with no partially-exposed failing rooms has nothing to grade, and
neither does any starting layout. The ramp is a mid-search signal by
construction, so experiments/ab_9gj_ramp.py defaults to seeding each run from
a 500k plateau artefact rather than cold.
The module-level math import replaces a now-redundant local one.
DESIGN.md 39.13 and the A/B verdict follow in a separate commit.
Refs homemaker-py-9gj.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MJ84Feep79Hhm3E4zZJmnB
Claude