FESADev/docs/shell-transient-heat-transfer/numerical-oracle-scratch.md

# 독립 numerical oracle scratch

이 파일은 numerical-review.md의 사전 계산을 재현하는 문서 부록이다. Solver 또는
production test가 아니며 외부 package·reference·출력 파일을 사용하지 않는다.
Python 표준 라이브러리만 사용한다. Fraction은 oracle에서 입력 double의 exact 산술을
확인하는 용도이며 production arbitrary-precision dependency를 요구하지 않는다.

T1 root에서 다음 명령은 각 Python block을 순서대로 메모리에서 실행한다.

```powershell
@'
from pathlib import Path
import re
p = Path('docs/shell-transient-heat-transfer/numerical-oracle-scratch.md')
blocks = re.findall(r'```python\n(.*?)```', p.read_text(encoding='utf-8-sig'), re.S)
assert len(blocks) == 4
scope = {}
for block in blocks:
    exec(compile(block, str(p), 'exec'), scope)
print('ALL SCRATCH BLOCKS COMPLETED')
'@ | python -
```

실행 exit는 0이어야 한다. Assertion 범위는 exact algebra와 독립 oracle 자체에 한정된다.
수렴/이산 오차의 출력 숫자 자체를 production tolerance로 사용하지 않고 본 보고서의
roundoff·conditioning·오차 전파 기준을 적용한다. NumPy 부재 probe exit1은 실행 실패
이력으로 보고서에 남겼으며 아래 코드에는 NumPy를 쓰지 않는다.

## A. Slab spectral·quadrature·공간/시간 oracle

```python
import math,json
def zeros(n,m=None): return [[0.0]*(n if m is None else m) for _ in range(n)]
def tr(A):return list(map(list,zip(*A)))
def mm(A,B):return [[sum(a*b for a,b in zip(row,col)) for col in zip(*B)]for row in A]
def mv(A,x):return [sum(a*b for a,b in zip(row,x)) for row in A]
def solve(A,b):
 a=[list(r)+[v]for r,v in zip(A,b)];n=len(b)
 for k in range(n):
  p=max(range(k,n),key=lambda i:abs(a[i][k]));a[k],a[p]=a[p],a[k]
  d=a[k][k]
  for j in range(k,n+1):a[k][j]/=d
  for i in range(n):
   if i!=k:
    d=a[i][k]
    for j in range(k,n+1):a[i][j]-=d*a[k][j]
 return [r[-1]for r in a]
def chol(A):
 n=len(A);L=zeros(n)
 for i in range(n):
  for j in range(i+1):
   v=A[i][j]-sum(L[i][k]*L[j][k]for k in range(j))
   L[i][j]=math.sqrt(v)if i==j else v/L[j][j]
 return L
def eig(A):
 a=[r[:]for r in A];n=len(a);v=[[float(i==j)for j in range(n)]for i in range(n)]
 for z in range(100*n*n):
  p,q=max(((i,j)for i in range(n)for j in range(i+1,n)),key=lambda ij:abs(a[ij[0]][ij[1]]))
  if abs(a[p][q])<1e-15*sum(abs(a[i][i])for i in range(n)):break
  phi=.5*math.atan2(2*a[p][q],a[q][q]-a[p][p]);c=math.cos(phi);s=math.sin(phi)
  J=[[float(i==j)for j in range(n)]for i in range(n)]
  J[p][p]=J[q][q]=c;J[p][q]=s;J[q][p]=-s
  a=mm(mm(tr(J),a),J);v=mm(v,J)
 ix=sorted(range(n),key=lambda i:a[i][i])
 return [a[i][i]for i in ix],[[v[j][i]for i in ix]for j in range(n)]
def slabmat(ne):
 n=2*ne+1;C=zeros(n);K=zeros(n);l=1/ne
 for e in range(ne):
  for i in range(3):
   for j in range(3):
    C[2*e+i][2*e+j]+=l/30*[[4,2,-1],[2,16,2],[-1,2,4]][i][j]
    K[2*e+i][2*e+j]+=[[7,-8,1],[-8,16,-8],[1,-8,7]][i][j]/(3*l)
 return C,K
C,K=slabmat(2);Cf=[r[1:]for r in C[1:]];Kf=[r[1:]for r in K[1:]]
L=chol(Cf);Li=tr([solve(L,[float(i==j)for i in range(4)])for j in range(4)])
lam,V=eig(mm(mm(Li,Kf),tr(Li)));W=mm(tr(Li),V)
yp=[-1-x for x in solve(Cf,[r[0]for r in C[1:]])]
coef=mv(tr(W),mv(Cf,yp))
def spectral(t,n=None):
 amp=[a*(math.exp(-l*t)if n is None else math.exp(-n*math.log1p(l*t/n)))for a,l in zip(coef,lam)]
 T=[1]+[1+x for x in mv(W,amp)]
 if n is None:dT=[0]+mv(W,[-l*x for l,x in zip(lam,amp)])
 else:
  oldamp=[x*(1+l*t/n)for l,x in zip(lam,amp)]
  old=[1]+[1+x for x in mv(W,oldamp)]
  dT=[(a-b)/(t/n)for a,b in zip(T,old)]
 E=sum(mv(C,T));R=mv(C,dT)[0]+mv(K,T)[0]
 q=[]
 for e,ss in [(0,-1),(0,0),(0,1),(1,-1),(1,0),(1,1)]:
  q.append(-4*sum(a*b for a,b in zip([ss-.5,-2*ss,ss+.5],T[2*e:2*e+3])))
 return T,q,E,R
def exact(t):
 M=80
 T=[1-sum(4/((2*m+1)*math.pi)*math.sin((2*m+1)*math.pi*x/2)*math.exp(-((2*m+1)*math.pi/2)**2*t)for m in range(M))for x in [0,.25,.5,.75,1]]
 q=[sum(2*math.cos((2*m+1)*math.pi*x/2)*math.exp(-((2*m+1)*math.pi/2)**2*t)for m in range(M))for x in [0,.25,.5,.5,.75,1]]
 E=1-sum(8/((2*m+1)*math.pi)**2*math.exp(-((2*m+1)*math.pi/2)**2*t)for m in range(M))
 return T,q,E,q[0]
def errors(a,b):return [max(abs(x-y)for x,y in zip(a[0],b[0])),max(abs(x-y)for x,y in zip(a[1],b[1])),abs(a[2]-b[2]),abs(a[3]-b[3])]
out={"lambda":lam,"projected_initial_free":[1+x for x in yp],"slab":[]}
for t in [.001,.01,.05,.1,.5,1]:
 s=spectral(t);x=exact(t)
 out["slab"].append({"t":t,"penetration":math.sqrt(t),"spatial_error":errors(s,x),"BE4096_temporal":errors(spectral(t,4096),s),"BE8192_temporal":errors(spectral(t,8192),s),"spectral":s})
print(json.dumps(out,indent=2))

def gauss(n):
 x=[];w=[]
 for i in range(1,n+1):
  z=math.cos(math.pi*(i-.25)/(n+.5))
  for _ in range(30):
   p0,p1=1.,z
   for j in range(2,n+1):p0,p1=p1,((2*j-1)*z*p1-(j-1)*p0)/j
   dp=n*(z*p1-p0)/(z*z-1);nz=z-p1/dp
   if abs(nz-z)<2e-16: z=nz;break
   z=nz
  x.append(z);w.append(2/((1-z*z)*dp*dp))
 return list(zip(x,w))
def dot(x,y):return sum(a*b for a,b in zip(x,y))
def cross(a,b):return [a[1]*b[2]-a[2]*b[1],a[2]*b[0]-a[0]*b[2],a[0]*b[1]-a[1]*b[0]]
def geometry(X,xi,eta):
 signs=[(-1,-1),(1,-1),(1,1),(-1,1)]
 N=[(1+s*xi)*(1+t*eta)/4 for s,t in signs]
 D=[[s*(1+t*eta)/4,t*(1+s*xi)/4]for s,t in signs]
 a=[sum(D[i][0]*X[i][j]for i in range(4))for j in range(3)]
 b=[sum(D[i][1]*X[i][j]for i in range(4))for j in range(3)]
 W=cross(a,b);J=math.sqrt(dot(W,W));norm=[z/J for z in W]
 aa,ab,bb=dot(a,a),dot(a,b),dot(b,b);det=J*J
 ra=[(bb*x-ab*y)/det for x,y in zip(a,b)];rb=[(aa*y-ab*x)/det for x,y in zip(a,b)]
 G=[[D[i][0]*ra[j]+D[i][1]*rb[j]for j in range(3)]for i in range(4)]
 return N,G,J,norm
def surface(X,n):
 M=zeros(4);S=zeros(4)
 for xi,wx in gauss(n):
  for eta,wy in gauss(n):
   N,G,J,no=geometry(X,xi,eta)
   for i in range(4):
    for j in range(4):
     M[i][j]+=N[i]*N[j]*J*wx*wy;S[i][j]+=dot(G[i],G[j])*J*wx*wy
 return M,S
Z0,Z1=slabmat(2)
# h=1: Z0 physical mass already; Z1 physical normal stiffness already.
def mats(X,n):
 M,S=surface(X,n);C=zeros(20);K=zeros(20)
 for i in range(4):
  for j in range(4):
   for a in range(5):
    for b in range(5):
     C[5*i+a][5*j+b]=M[i][j]*Z0[a][b]
     K[5*i+a][5*j+b]=S[i][j]*Z0[a][b]+M[i][j]*Z1[a][b]
 return C,K
def fn(A):return math.sqrt(sum(x*x for r in A for x in r))
def rel(A,B):return fn([[a-b for a,b in zip(r,s)]for r,s in zip(A,B)])/fn(B)
def response(X,C,K):
 A=[[c/.1+k for c,k in zip(cr,kr)]for cr,kr in zip(C,K)]
 T=solve(A,[float(i==0)for i in range(20)])
 flux=[]
 for xi,eta in [(-1/math.sqrt(3),-1/math.sqrt(3)),(1/math.sqrt(3),-1/math.sqrt(3)),(1/math.sqrt(3),1/math.sqrt(3)),(-1/math.sqrt(3),1/math.sqrt(3))]:
  N,G,J,no=geometry(X,xi,eta)
  for off,s in [(0,-1),(0,0),(0,1),(2,-1),(2,0),(2,1)]:
   Ls=[s*(s-1)/2,1-s*s,s*(s+1)/2];Ds=[4*(s-.5),-8*s,4*(s+.5)]
   flux.append([-sum((G[i][j]*Ls[a]+no[j]*N[i]*Ds[a])*T[5*i+off+a]for i in range(4)for a in range(3))for j in range(3)])
 return T,flux
def rv(a,b):return math.sqrt(sum((x-y)**2 for x,y in zip(a,b)))/math.sqrt(sum(x*x for x in b))
cases={"affine":[[0,0,0],[1,0,0],[1,1,0],[0,1,0]],"distorted":[[0,0,0],[2,0,0],[1.5,1,0],[0,1,0]]}
for w in [.1,.5,2]:cases["saddle"+str(w)]=[[x,y,w*x*y]for x,y in [(-1,-1),(1,-1),(1,1),(-1,1)]]
ans={}
for name,X in cases.items():
 ds=[]
 for n in [3,5,7]:
  C,K=mats(X,n);T,q=response(X,C,K);ds.append((C,K,T,q))
 rows=[]
 for a,b in [(ds[0],ds[1]),(ds[1],ds[2])]:
  rows.append([rel(a[0],b[0]),rel(a[1],b[1]),rv(a[2],b[2]),max(math.sqrt(dot([x-y for x,y in zip(q,r)],[x-y for x,y in zip(q,r)]))for q,r in zip(a[3],b[3]))/max(math.sqrt(dot(r,r))for r in b[3])])
 ans[name]=rows
print(json.dumps({"quadrature":ans},indent=2))
# Independent uniform Q1 Neumann mode and continuum error by high-order integral.
def spatial(n):
 h=1/n;lam=6*(1-math.cos(math.pi/n))/(h*h*(2+math.cos(math.pi/n)))
 t=.1;af=math.exp(-lam*t);ae=math.exp(-math.pi**2*t);et=eg=0
 for i in range(n):
  for s,w in gauss(12):
   x=(i+(s+1)/2)*h
   T=af*((1-s)*math.cos(math.pi*i/n)+(1+s)*math.cos(math.pi*(i+1)/n))/2
   G=af*(math.cos(math.pi*(i+1)/n)-math.cos(math.pi*i/n))/h
   et+=(T-ae*math.cos(math.pi*x))**2*w*h/2
   eg+=(G+math.pi*ae*math.sin(math.pi*x))**2*w*h/2
 return math.sqrt(et),math.sqrt(eg)
ss=[spatial(n)for n in [8,16,32,64]]
print(json.dumps({"spatial_errors":ss,"orders":[[math.log(a/b,2)for a,b in zip(ss[i],ss[i+1])]for i in range(3)]},indent=2))
print(json.dumps({"time_orders":[math.log(abs((1+1/n)**(-n)-math.exp(-1))/abs((1+1/(2*n))**(-2*n)-math.exp(-1)),2)for n in [16,32,64,128]]}))


def direct54(X):
 C=zeros(20);K=zeros(20)
 for xi,wx in gauss(3):
  for eta,wy in gauss(3):
   N,G,J,no=geometry(X,xi,eta)
   for off in [0,2]:
    for s,ws in gauss(3):
     ls=[s*(s-1)/2,1-s*s,s*(s+1)/2]
     ds=[4*(s-.5),-8*s,4*(s+.5)]
     H=[0.]*20;B=zeros(20,3)
     for i in range(4):
      for a in range(3):
       p=5*i+off+a;H[p]=N[i]*ls[a]
       B[p]=[G[i][j]*ls[a]+no[j]*N[i]*ds[a]for j in range(3)]
     weight=wx*wy*ws*J/4
     for i in range(20):
      for j in range(20):
       C[i][j]+=weight*H[i]*H[j];K[i][j]+=weight*dot(B[i],B[j])
 return C,K
for name,X in cases.items():
 C,K=mats(X,3);Cd,Kd=direct54(X)
 print("54point",name,rel(C,Cd),rel(K,Kd))
 assert rel(C,Cd)<1e-12 and rel(K,Kd)<1e-12
# Generalized eigen residual and C orthogonality, independently reassemble.
C,K=slabmat(2);Cf=[r[1:]for r in C[1:]];Kf=[r[1:]for r in K[1:]]
res=fn([[a-b*l for a,b,l in zip(kr,cr,lam)]for kr,cr in zip(mm(Kf,W),mm(Cf,W))])/fn(mm(Kf,W))
orth=fn([[v-float(i==j)for j,v in enumerate(row)]for i,row in enumerate(mm(mm(tr(W),Cf),W))])
print("slab eigen residual",res,"C orthogonality",orth)
assert res<1e-12 and orth<1e-12

def spatial_full(n,ng):
 h=1/n;t=.1;steps=16*n*n
 l=6*(1-math.cos(math.pi/n))/(h*h*(2+math.cos(math.pi/n)))
 af=math.exp(-steps*math.log1p(l*t/steps));ase=math.exp(-l*t);ae=math.exp(-math.pi**2*t)
 et=eg=etime=0
 for i in range(n):
  for s,w in gauss(ng):
   x=(i+(s+1)/2)*h
   v=((1-s)*math.cos(math.pi*i/n)+(1+s)*math.cos(math.pi*(i+1)/n))/2
   G=af*(math.cos(math.pi*(i+1)/n)-math.cos(math.pi*i/n))/h
   et+=(af*v-ae*math.cos(math.pi*x))**2*w*h/2
   eg+=(G+math.pi*ae*math.sin(math.pi*x))**2*w*h/2
   etime+=((af-ase)*v)**2*w*h/2
 return math.sqrt(et),math.sqrt(eg),math.sqrt(etime)
sbe=[]
for n in [8,16,32,64]:
 a=spatial_full(n,12);b=spatial_full(n,16)
 er=spatial(n)[0];ratio=a[2]/er
 quadr=max(abs(x-y)/abs(x)for x,y in zip(a,b))
 assert ratio<=1/32 and quadr<=1e-8
 sbe.append(a)
 print("spatial BE",n,"time/spatial",ratio,"12/16 relative change",quadr)
for i in range(3):
 pt=math.log(sbe[i][0]/sbe[i+1][0],2);pg=math.log(sbe[i][1]/sbe[i+1][1],2)
 assert 1.95<=pt<=2.05 and .98<=pg<=1.03
 print("spatial BE order",pt,pg)


```

## B. Exact Fraction integration·rank·jump

```python

from fractions import Fraction as F
def fmat(A,d):return [[F(v,d)for v in r]for r in A]
def mul(a,b):
 c=[F(0)]*(len(a)+len(b)-1)
 for i,x in enumerate(a):
  for j,y in enumerate(b):c[i+j]+=x*y
 return c
def der(a):return [i*a[i] for i in range(1,len(a))]
def integ(a):return sum(F(x,i+1)for i,x in enumerate(a))
sh=[[1,-3,2],[0,4,-4],[0,-1,2]]
assert [[integ(mul(a,b))for b in sh]for a in sh]==fmat([[4,2,-1],[2,16,2],[-1,2,4]],30)
assert [[integ(mul(der(a),der(b)))for b in sh]for a in sh]==fmat([[7,-8,1],[-8,16,-8],[1,-8,7]],3)
M=fmat([[4,2,1,2],[2,4,2,1],[1,2,4,2],[2,1,2,4]],36)
S=fmat([[4,-1,-2,-1],[-1,4,-1,-2],[-2,-1,4,-1],[-1,-2,-1,4]],6)
fac=[([1,-1],[1,-1]),([0,1],[1,-1]),([0,1],[0,1]),([1,-1],[0,1])]
assert [[integ(mul(a,c))*integ(mul(b,d))for c,d in fac]for a,b in fac]==M
assert [[integ(mul(der(a),der(c)))*integ(mul(b,d))+integ(mul(a,c))*integ(mul(der(b),der(d)))for c,d in fac]for a,b in fac]==S
Z0=[[F(0)for _ in range(5)]for _ in range(5)]
Z1=[[F(0)for _ in range(5)]for _ in range(5)]
for off in [0,2]:
 for i in range(3):
  for j in range(3):
   Z0[i+off][j+off]+=F([[4,2,-1],[2,16,2],[-1,2,4]][i][j],30)
   Z1[i+off][j+off]+=F([[7,-8,1],[-8,16,-8],[1,-8,7]][i][j],3)
C=[[M[i//5][j//5]*Z0[i%5][j%5]for j in range(20)]for i in range(20)]
K=[[S[i//5][j//5]*Z0[i%5][j%5]+M[i//5][j//5]*Z1[i%5][j%5]for j in range(20)]for i in range(20)]
def pivots(A):
 a=[r[:]for r in A];p=[]
 for k in range(len(a)):
  d=a[k][k];p.append(d)
  for i in range(k+1,len(a)):
   for j in range(k+1,len(a)):a[i][j]-=a[i][k]*a[k][j]/d
 return p
assert all(x>0 for x in pivots(C))
assert all(x>0 for x in pivots([r[:19]for r in K[:19]]))
assert all(sum(r)==0 for r in K)
assert sum(map(sum,C))==2
cc=[[F(2),F(1)],[F(1),F(2)]];kk=[[F(1),F(-1)],[F(-1),F(1)]]
old=[F(0),F(0)]
for expected,react in [(F(-1,5),F(24,5)),(F(1,25),F(36,25))]:
 new=[(2*(2*old[0]+old[1])-1)/5,F(1)]
 r=[2*sum(cc[i][j]*(new[j]-old[j])for j in range(2))+sum(kk[i][j]*new[j]for j in range(2))for i in range(2)]
 assert new[0]==expected and r==[0,react]
 assert 3*sum(new[j]-old[j]for j in range(2))==react/2
 old=new
print("exact: C SPD 20/20; K rank19; K1=0; 1TC1=2; jump -1/5,1/25; Rc 24/5,36/25")

```

## C. Time predicate와 경계

```python

import math,random,struct
from fractions import Fraction as F
def input_cell(x):
 v=F(x);prev=F(math.nextafter(x,-math.inf))
 nxt=math.nextafter(x,math.inf)
 hi=(v+F(nxt))/2 if math.isfinite(nxt) else v+(v-prev)/2
 even=not(struct.unpack('>Q',struct.pack('>d',x))[0]&1)
 return (prev+v)/2,hi,even
def cell_overlap(t,d,m):
 a,b,ca=input_cell(t);c,e,cb=input_cell(d);c*=m;e*=m
 lo=max(a,c);hi=min(b,e)
 return lo<hi or (lo==hi and (ca or (a<lo<b)) and (cb or (c<lo<e)))
def dyadic_overlap(t,d,m):
 _,ex=math.frexp(t)
 factor=F(2)**(-ex)
 aa,bb,ca=input_cell(t);cc,ee,cb=input_cell(d)
 ints=[]
 for x in [aa,bb,cc,ee]:
  z=x*factor*2**88
  assert z.denominator==1
  ints.append(z.numerator)
 a,b,c,e=ints;c*=m;e*=m
 assert max(z.bit_length()for z in [a,b,c,e])<=122
 lo=max(a,c);hi=min(b,e)
 return lo<hi or (lo==hi and (ca or (a<lo<b)) and (cb or(c<lo<e)))
def fm(a,b,c):return float(F(a)*F(b)+F(c))
def grid_cell(t,d,inc=100):
 if not(math.isfinite(t)and math.isfinite(d)and t>0 and d>0 and type(inc)is int and 1<=inc<=2**32-1):return "input-error"
 if d>=t:return 1,False,t
 if F(t)/F(d)>inc+1:return "INC"
 _,e=math.frexp(t);q=math.ldexp(t,-e)/math.ldexp(d,-e);m=round(q)
 close=cell_overlap(t,d,m)
 assert close==dyadic_overlap(t,d,m)
 if close:n=m
 else:
  factor=F(2)**(-e+88);X=F(t)*factor;Y=F(d)*factor
  assert X.denominator==Y.denominator==1
  X=int(X);Y=int(Y);f=math.floor(q)
  if f*Y>X:f-=1
  elif (f+1)*Y<=X:f+=1
  assert f*Y<=X<(f+1)*Y
  n=f if X==f*Y else f+1
 if n>inc:return "INC"
 if not close:assert n==-(-F(t)//F(d))
 delta=d if close else fm(-(n-1),d,t)
 assert 0<delta<=d and math.isfinite(delta)
 assert (n-1)*d<t
 return n,close,delta
pairs=[(10.,3.),(2.,3.),(.9,.3),(math.nextafter(.9,math.inf),.3),
(5.351455173733616,.17262758624947144),
(20*math.ulp(0.),6*math.ulp(0.)),(17*math.ulp(0.),5*math.ulp(0.)),
(math.nextafter(math.inf,0.),math.nextafter(math.inf,0.)/3)]
for t,d in pairs:print("input-cell grid",repr(t),repr(d),grid_cell(t,d))
rng=random.Random(901)
count=0
for i in range(10000):
 m=rng.randint(2,2**32-1);d=math.ldexp(rng.uniform(.5,1),rng.randint(-1073,990))
 t=m*d
 if not(math.isfinite(t)and d>0):continue
 t=math.nextafter(t,math.inf if i%2 else -math.inf)
 if not math.isfinite(t):continue
 q=t/d
 if not math.isfinite(q)or q>2**32:continue
 mm=round(q)
 assert cell_overlap(t,d,mm)==dyadic_overlap(t,d,mm)
 count+=1
print("input-cell/fixed-dyadic independent comparisons",count)
assert grid_cell(5.351455173733616,.17262758624947144)[0]==31
assert grid_cell(math.nextafter(.9,math.inf),.3)[0]==4
assert grid_cell(20*math.ulp(0.),6*math.ulp(0.))[0]==3
assert grid_cell(17*math.ulp(0.),5*math.ulp(0.))[0]==4
print("INPUT-CELL ASSERTIONS PASSED")

for t,d in [(1.,.1),(math.ldexp(.9,-1000),math.ldexp(.3,-1000)),(math.ldexp(.9,1000),math.ldexp(.3,1000)),(1e-323,5e-324)]:
 print("input-cell scale",repr(t),repr(d),grid_cell(t,d))
assert grid_cell(10.,3.,3)=="INC" and grid_cell(10.,3.,4)[0]==4
assert grid_cell(float(2**32),1.,2**32-1)=="INC"
for bad in [0,-1,1.5,2**32]:assert grid_cell(1.,.1,bad)=="input-error"
for bad in [0.,-1.,math.inf,math.nan]:assert grid_cell(bad,.1)=="input-error"
print("CURRENT TIME GRID ASSERTIONS PASSED")

```

## D. 입력 rounding-cell의 독립 반증 검색

고정 seed의 검색은 폐기된 arithmetic-only predicate와 입력 rounding-cell의 차이를
검출한다. 이 출력은 predicate 실행 성공과 승인 시간 의미의 정합을 구별하기 위한
반증 evidence다. 상세 판정은 numerical-review.md §8을 따른다.

```python

import math,random
from fractions import Fraction as F
def rad(x):return max(x-math.nextafter(x,-math.inf),math.nextafter(x,math.inf)-x)/2
def pred(t,d,m):
 q=t/d;p=m*d
 B=math.nextafter(d*rad(q)+rad(p),math.inf)
 return abs(float(F(t)-m*F(d)))<=B,B
rng=random.Random(41);found=[]
for z in range(20000):
 d=rng.uniform(.125,.25);m=rng.randint(2,100);t=m*d
 for dr in [-1,1]:
  tt=math.nextafter(t,math.inf if dr>0 else -math.inf)
  loT=(F(tt)+F(math.nextafter(tt,-math.inf)))/2
  hiT=(F(tt)+F(math.nextafter(tt,math.inf)))/2
  loD=(F(d)+F(math.nextafter(d,-math.inf)))/2
  hiD=(F(d)+F(math.nextafter(d,math.inf)))/2
  overlap=max(loT,m*loD)<=min(hiT,m*hiD)
  ok,B=pred(tt,d,m)
  if overlap and not ok:
   found.append((tt,d,m,float(abs(F(tt)-m*F(d))),B));break
 if found:break
print("input-cell overlap rejected by retired arithmetic predicate:",found)
t=math.nextafter(.9,math.inf);d=.3;m=3
print("specific .9 upper:",float(F(t)-m*F(d)),rad(t)+m*rad(d),"input-cell overlap",abs(F(t)-m*F(d))<=F(rad(t))+m*F(rad(d)))

```