Files
sim-numerics/tests/test_extrapolate.py
T
vvsandClaude Opus 5 68df1d25db Sign tests by product underflowed: FIXED everywhere (branch, not master - the paper is not yet updated). FA * fnew < 0.0 with FA ~ -1e-200, fnew ~ 1e-150 is -0.0 and '-0.0 < 0.0' is False, so on flat functions (x^19) the bracket update moved the wrong end, the root left the bracket and the run still reported convergence - the proposed rule returned 4.9e-9, bisection 3.5e-9, ITP 1.6e-8 with a claimed 1e-12 bracket; the 1e-6 harness scored them solved. Same defect in our bisection, false-position family, Ridders, Brent, ITP and twelve copies in stage scripts, simroot/sim.py and one test; all replaced by _opposite / _same_sign, pinned by test_sign_underflow.
Impact, every sweep regenerated: the paper's key configurations are unchanged to the evaluation (proposed 2806/3220, credit 3568/3020, Chandrupatla, TOMS 748, Brent, bisection); 46 stated numbers move (ITP CHA 2857 -> 2896, ITP oracle 2611 -> 2647, record CHA figures by 14-18, the grid means by ~1%) and one finding weakens: the measured-order exponent of section 7.1 was cheaper in 29 of 60 far cells and 7 of 7 safeguards; with the fix 12 of 61 and 6 of 7, and on the wide-bracket set it now loses in every safeguard and drops 5 problems.

PREREG G1-G3 outcome on the fixed code: G2 (repeating step pattern, period from the data) PASSES Y1-Y4 and is ACCEPTED by the stop rule - proposed rule APS 2806 -> 2782 (below Chandrupatla's 2787), CHA 3220 -> 3169, both 6026 -> 5951, per problem vs Chandrupatla on APS 95/20/38 p = 8e-7. G1 fails Y1/Y2 (its Y3 miss was the sign bug), G3 fails Y2, A fails Y2. Regression 887 pass; the two red tests are the paper-number check (awaiting the paper update) and test_blend (fixed since, copy in stage16).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-09-21 12:49:01 +01:00

119 lines
5.0 KiB
Python

"""Pins for PREREG_extrapolate_in_method_2026-09-21.md: step extrapolation (A)."""
from __future__ import annotations
import math
import pytest
from simroot.pure import pure_root
SMOOTH = (
(lambda t: t ** 3 - 2.0 * t - 5.0, 1.0, 4.0),
(lambda t: math.exp(t) - 2.0, 0.0, 3.0),
(lambda t: math.sin(t) - 0.5, 0.0, 1.5),
)
FLAT = (
(lambda t: 6.0 * (t - 2.0) ** 5, 0.0, 10.0),
(lambda t: t ** 9, -1.0, 2.0),
(lambda t: (t - 3.0) ** 3, 0.0, 10.0),
)
XTOL, MAXFEV = 1e-12, 200
@pytest.mark.parametrize("f,a,b", SMOOTH + FLAT)
@pytest.mark.parametrize("guard", ("project", "safe", "credit"))
def test_default_is_the_published_method_bit_for_bit(f, a, b, guard):
ref = pure_root(f, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3", guard=guard)
off = pure_root(f, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3", guard=guard,
extrapolate="none")
assert ref == off
@pytest.mark.parametrize("f,a,b", SMOOTH + FLAT)
@pytest.mark.parametrize("guard", ("project", "credit"))
def test_the_guarantee_survives_extrapolation(f, a, b, guard):
x, n, ok = pure_root(f, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3",
guard=guard, extrapolate="steps")
assert ok and min(a, b) <= x <= max(a, b)
half = math.ceil(math.log2(abs(b - a) / XTOL))
bound = 2 * half + 3 if guard == "project" else half + 4
assert n <= bound, (n, bound)
@pytest.mark.parametrize("f,a,b", FLAT[1:])
def test_extrapolation_breaks_the_flat_cycle(f, a, b):
"""The mechanism the pre-registration rests on: on a pure power the similar successive
undershoots are replaced by a longer step, and the run gets cheaper."""
_x, n_off, _ = pure_root(f, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3",
guard="project")
_x, n_on, _ = pure_root(f, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3",
guard="project", extrapolate="steps")
assert n_on < n_off, (n_on, n_off)
def test_on_a_budget_bound_run_extrapolation_changes_the_path_not_the_count():
"""MEASURED, pinned as measured: on 6(x-2)^5 over [0, 10] both runs cost 90 evaluations
against a projection guarantee of 2*44 + 3 = 91 - the budget schedule, not the step,
decides when the run ends. The paths differ from the fourth evaluation on (87
positions), so the mode is active; its gain is absorbed by the safeguard here. The
expectation written first (strictly fewer evaluations) was wrong for this problem."""
f, a, b = FLAT[0]
ev = {}
for mode in ("none", "steps"):
seen = []
def g(t, _s=seen):
_s.append(t)
return f(t)
_x, n, ok = pure_root(g, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3",
guard="project", extrapolate=mode)
assert ok
ev[mode] = (n, seen)
assert ev["steps"][0] <= ev["none"][0]
assert ev["steps"][1] != ev["none"][1]
GATES = ("confirmed", "pattern", "steps+results")
@pytest.mark.parametrize("mode", GATES)
@pytest.mark.parametrize("f,a,b", SMOOTH + FLAT)
@pytest.mark.parametrize("guard", ("project", "credit"))
def test_every_gate_keeps_the_guarantee(mode, f, a, b, guard):
x, n, ok = pure_root(f, a, b, XTOL, MAXFEV, similarity="ratio", scale="derived3",
guard=guard, extrapolate=mode)
assert ok and min(a, b) <= x <= max(a, b)
half = math.ceil(math.log2(abs(b - a) / XTOL))
assert n <= (2 * half + 3 if guard == "project" else half + 4), (mode, n)
def test_the_gates_decline_without_history():
"""Each gate needs history to confirm anything; without it the step is untouched."""
from simroot.pure import _extrapolation_s
# opposite directions -> nothing to confirm, in every mode
for mode in ("steps",) + GATES:
assert _extrapolation_s(mode, 0.1, 1.0, 1.5, None, 1.0, 2.0, None, []) == 0.0
# same direction, but G1 has no third point, G3 no third value, G2 no history
assert _extrapolation_s("confirmed", 0.1, 1.0, 0.8, None, 1.0, 2.0, None, []) == 0.0
assert _extrapolation_s("steps+results", 0.1, 1.0, 0.8, None, 1.0, 2.0, None, []) == 0.0
assert _extrapolation_s("pattern", 0.1, 1.0, 0.8, None, 1.0, 2.0, None, [0.2]) == 0.0
def test_results_after_a_crossing_confirm_nothing():
"""G3: a sign change of f between the last results is a crossing, not a creep."""
from simroot.pure import _extrapolation_s
assert _extrapolation_s("steps+results", 0.1, 1.0, 0.9, 0.8, 1.0, -2.0, 4.0, []) == 0.0
assert _extrapolation_s("steps+results", 0.1, 1.0, 0.9, 0.8, 1.0, 2.0, 4.0, []) > 0.0
def test_a_confirmed_geometric_series_is_read_exactly():
"""G1 on three moves in ratio 0.5, 0.5: fully confirmed, s = q2 = 0.5."""
from simroot.pure import _extrapolation_s
s = _extrapolation_s("confirmed", 0.025, 1.0, 0.95, 0.85, 1.0, 2.0, 4.0, [])
assert s == pytest.approx(0.5)
def test_unknown_mode_is_refused():
with pytest.raises(ValueError):
pure_root(lambda t: t, -1.0, 1.0, XTOL, MAXFEV, extrapolate="aitken")