Paper A v4.1: BCD-baseline reframe + screening positioning + trim

- Re-anchor inter-CPA coincidence-rate (ICCR) calibration on a normative
  non-Firm-A baseline (Firms B/C/D); Firm A held out as an out-of-sample
  target. Locked canonical numbers (codex-audited; Scripts 46/52/53):
  per-comparison HC 0.00014->0.000018, per-signature HC 0.0116, per-document
  HC+MC 0.34->0.1905; KDE crossover 0.837 retained corpus-wide.
- Reposition as an operator-tunable, semi-automated screening/triage framework
  (title -> "Automated Screening..."): HC = high-specificity operating point;
  MC band demoted to low-specificity advisory; Firm A = demonstration that the
  screening surfaces a templated end, audit-quality implications deferred.
- Apply codex prose-review fixes: triage-neutral five-way labels, soften
  mechanism/specificity wording, supersede MC claim-strength, update stale
  Appendix script references (40b/43/45 -> 46/52/53).
- Trim pass: compress Sec. V discussion + Sec. III echoes (27.7k -> 26.8k
  words); no substantive content removed.
- Add analysis scripts 45-53 (firm-year trends; BCD-only ICCR recompute;
  canonical-sampler locked numbers; Firm-A out-of-sample; BCD regression +
  cross-firm hit matrix).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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2026-06-04 19:35:10 +08:00
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#!/usr/bin/env python3
"""Script 53: BCD-only firm-effect logistic regression (Firm D reference) and
BCD-only cross-firm hit matrix. Candidate pool = BCD (exclude Firm A and
same-CPA). Canonical retry-loop sampler, any-pair + same-pair. Read-only.
Replicates Script 44's logistic_fit and matrix logic, restricted to BCD.
"""
import sqlite3
from collections import defaultdict
import numpy as np
DB = '/Volumes/NV2/PDF-Processing/signature-analysis/signature_analysis.db'
FIRM_A = '勤業眾信聯合'
BIG4 = ('勤業眾信聯合', '安侯建業聯合', '資誠聯合', '安永聯合')
ALIAS = {'勤業眾信聯合': 'A', '安侯建業聯合': 'B', '資誠聯合': 'C', '安永聯合': 'D'}
SEED = 42
POP = np.array([bin(i).count('1') for i in range(256)], dtype=np.uint8)
def logistic_fit(X, y, max_iter=200, l2=0.001):
n, k = X.shape
beta = np.zeros(k)
for _ in range(max_iter):
eta = np.clip(X @ beta, -30, 30)
p = 1.0/(1.0+np.exp(-eta))
grad = X.T @ (y-p) - l2*beta
W = p*(1-p)
H = -(X.T*W) @ X - l2*np.eye(k)
try:
delta = np.linalg.solve(H, grad)
except np.linalg.LinAlgError:
delta = 0.3*grad
nb = beta - delta
if np.max(np.abs(nb-beta)) < 1e-8:
beta = nb; break
beta = nb
eta = np.clip(X @ beta, -30, 30)
p = 1.0/(1.0+np.exp(-eta)); W = p*(1-p)
cov = np.linalg.inv((X.T*W) @ X + l2*np.eye(k))
return beta, np.sqrt(np.diag(cov))
conn = sqlite3.connect(f'file:{DB}?mode=ro', uri=True)
cur = conn.cursor()
cur.execute("""SELECT s.assigned_accountant, a.firm, s.feature_vector, s.dhash_vector
FROM signatures s JOIN accountants a ON s.assigned_accountant=a.name
WHERE s.assigned_accountant IS NOT NULL AND a.firm IN (?,?,?)
AND s.feature_vector IS NOT NULL AND s.dhash_vector IS NOT NULL""",
('安侯建業聯合', '資誠聯合', '安永聯合'))
rows = cur.fetchall()
conn.close()
n = len(rows)
feats = np.stack([np.frombuffer(r[2], np.float32) for r in rows]).astype(np.float32)
norms = np.linalg.norm(feats, axis=1, keepdims=True); norms[norms == 0] = 1.0
feats = feats / norms
dh = np.stack([np.frombuffer(r[3], np.uint8) for r in rows])
cpas = np.array([r[0] for r in rows])
firms = np.array([ALIAS[r[1]] for r in rows])
cpa_idx = defaultdict(list)
for i, c in enumerate(cpas):
cpa_idx[c].append(i)
cpa_idx = {c: np.array(v) for c, v in cpa_idx.items()}
pool_size = {c: len(v)-1 for c, v in cpa_idx.items()}
all_idx = np.arange(n)
print(f'BCD signatures: {n:,}; CPAs: {len(cpa_idx)}')
rng = np.random.default_rng(SEED)
hit_any = np.zeros(n, bool)
hit_same = np.zeros(n, bool)
cand_firm_maxcos = np.empty(n, dtype=object) # any-pair partner firm
cand_firm_same = np.empty(n, dtype=object)
psize = np.zeros(n, np.int32)
for si in range(n):
np_ = pool_size[cpas[si]]; psize[si] = np_
if np_ <= 0:
continue
same = cpa_idx[cpas[si]]
need = np_; cand = []; att = 0
while need > 0 and att < 10:
draw = rng.choice(n, size=need*2, replace=True)
ok = draw[~np.isin(draw, same)]
cand.extend(ok[:need].tolist()); need -= len(ok[:need]); att += 1
if need > 0:
pm = np.ones(n, bool); pm[same] = False
cand.extend(rng.choice(all_idx[pm], size=need, replace=False).tolist())
cand = np.array(cand[:np_], dtype=np.int64)
cosv = feats[cand] @ feats[si]
dist = POP[dh[cand] ^ dh[si]].sum(axis=1)
mc = int(np.argmax(cosv)); md = int(np.argmin(dist))
if cosv[mc] > 0.95 and dist[md] <= 5:
hit_any[si] = True
cand_firm_maxcos[si] = firms[cand[mc]]
spm = (cosv > 0.95) & (dist <= 5)
if spm.any():
hit_same[si] = True
cand_firm_same[si] = firms[cand[int(np.argmax(spm))]]
# ---- Logistic regression: hit_any ~ FirmB + FirmC + log(pool), Firm D reference ----
hp = psize > 0
y = hit_any[hp].astype(np.float64)
fa = firms[hp]
lp = np.log(psize[hp].astype(np.float64)); lp = lp - lp.mean()
X = np.column_stack([np.ones(y.shape), (fa == 'B').astype(float), (fa == 'C').astype(float), lp])
beta, se = logistic_fit(X, y)
print(f'\n[BCD logistic: hit_any ~ FirmB + FirmC + log(pool); Firm D = reference] n={len(y):,}, y_mean={y.mean():.4f}')
for nm, b, s in zip(['intercept(FirmD)', 'FirmB', 'FirmC', 'log(pool,centred)'], beta, se):
print(f' {nm}: beta={b:+.4f} SE={s:.4f} OR={np.exp(b):.4f} z~{abs(b)/s if s>0 else float("inf"):.2f}')
# ---- Cross-firm hit matrix (any-pair max-cos partner) ----
print('\n[BCD cross-firm hit matrix: any-pair, source firm x max-cos partner firm]')
print(' src -> B C D | within-firm% (n hits)')
for sf in ['B', 'C', 'D']:
m = (firms == sf) & hit_any
parts = cand_firm_maxcos[m]
tot = len(parts)
cnt = {f: int((parts == f).sum()) for f in ['B', 'C', 'D']}
wf = cnt[sf]/tot if tot else 0
print(f' {sf} {cnt["B"]:5d} {cnt["C"]:5d} {cnt["D"]:5d} | {wf:6.1%} ({tot})')
print('\n[BCD same-pair within-firm concentration]')
for sf in ['B', 'C', 'D']:
m = (firms == sf) & hit_same
parts = cand_firm_same[m]; tot = len(parts)
wf = int((parts == sf).sum())/tot if tot else 0
print(f' Firm {sf}: {wf:.1%} within-firm ({int((parts==sf).sum())}/{tot})')